PCS TR 013 Public Trasport Modal Shift_v1.0

Document Control

Document identification

• Document code: PCS-TR-013

• Title: Public Transport Modal Shift Methodology

• Scope: Defines eligibility conditions, boundary and baseline determination rules, additionality requirements, monitoring requirements, leakage treatment, and calculation procedures for PCS projects that shift passenger travel from higher-emitting baseline modes to eligible public transport modes and achieve net GHG emission reductions without reducing service output.

Version history and change log

Table DC-1. Revision history

Version	Date	Status	Summary of changes	Prepared by	Approved by
v1.0	TBD	Draft	Release for public consultation	PCS	TBD

Superseded versions

No superseded versions for v1.0.

Governance note on versioning and archiving

Only the latest approved version of this Methodology shall be used. Superseded versions shall be archived and retained for traceability and audit purposes. Printed or downloaded copies are uncontrolled; stakeholders must refer to the PCS-published version as the authoritative current version.

Chapter 1 - Purpose

1.1 Purpose

This methodology establishes requirements for quantifying emission reductions from projects that cause a measurable and verifiable shift of passenger travel from higher-emitting baseline transport modes to eligible public transport modes under the Planetary Carbon Standard (PCS). It sets requirements for eligibility, baseline scenario determination, project boundary definition, monitoring and calculation procedures, and conservative leakage treatment so that credited reductions reflect real, additional, and verifiable net climate benefits.

1.2 Intended use

This methodology shall be applied to projects where passenger travel is shifted to eligible public transport services and where the project proponent can demonstrate, using auditable data, that baseline travel would have occurred using identifiable baseline modes and that the project results in net emissions reductions after accounting for project service emissions.

This methodology is designed to prevent over-crediting that can arise from weak attribution of passenger behaviour, double counting with vehicle electrification or fuel switch claims, and crediting that is driven by reduced travel rather than mode shift.

1.3 Relationship to other PCS documents

This methodology shall be applied together with applicable PCS standards, any PCS methodological tools referenced by this methodology, and the approved PCS templates and forms used for project submission and monitoring/reporting. In the event of inconsistency, higher-order PCS documents prevail.

1.4 Binding nature

Requirements expressed using “shall” are mandatory. Where this methodology references a methodological tool, that tool shall be applied as specified. PCS templates and forms required for submissions shall be used without substitution unless an explicit exception is granted through the PCS deviation process.

1.5 Version control and applicability

This methodology is subject to controlled versioning. The applicable version is the version in force at the time of project submission unless transition provisions specify otherwise. Revisions do not apply until they enter into force under PCS governance procedures.

Chapter 2 - Scope and Applicability

2.1 Scope

This methodology applies to projects that reduce GHG emissions by shifting passenger travel from baseline modes to eligible public transport modes, where the project results in a measurable change in travel behaviour and where emissions can be quantified on a service-equivalent basis.

The methodology is designed for situations where the project can establish a credible baseline for the modes displaced, can quantify passenger travel shifted using auditable activity data, and can quantify project service emissions attributable to the shifted travel.

2.2 Eligible project types

Eligible projects include interventions that demonstrably increase passenger travel on eligible public transport services and thereby displace travel that would otherwise occur using higher-emitting baseline modes. Eligible interventions may include network improvements, service frequency enhancements, fare integration and ticketing systems, demand management measures tied to public transport use, station and access improvements, and other measures that can be linked to measurable modal shift.

Eligible public transport modes may include buses, bus rapid transit, metro, light rail, commuter rail, ferries, and other mass transit services where passenger travel and service emissions can be quantified credibly.

Projects may be implemented by transport authorities, operators, concessionaires, or other entities, provided that the right to claim emission reductions is demonstrated and double counting risks are controlled.

2.3 Non-eligible and excluded cases

This methodology shall not be applied where the claimed emission reductions are primarily due to reduced passenger travel rather than mode shift, including cases where travel demand is suppressed by service reduction, access restrictions, or other factors that reduce mobility service.

This methodology shall not be applied where the project cannot demonstrate that incremental public transport ridership represents displacement from identifiable baseline modes rather than primarily induced demand, mode shift from already low-emission modes, or demographic and macroeconomic trends not attributable to the project.

This methodology shall not be applied where the same emission reductions are claimed under another PCS methodology for the same activity, including electrification of the same service under an electric mobility methodology, fuel switch claims for the same fleet, or other overlapping project claims. Where multiple measures occur in the same system, boundaries and claims shall be separated to avoid overlap.

Projects that are legally mandated in a way that would deliver the same modal shift outcomes absent the project are not eligible.

2.4 Applicability conditions

A project shall be applicable under this methodology only where it can define and evidence the following elements in a manner suitable for validation and verification.

The project shall define the eligible public transport service(s), the geographic service area, and the intervention(s) that are asserted to cause modal shift.

The project shall define the passenger travel metric used for quantification, such as passenger-kilometres, boardings with distance attribution, or other PCS-accepted metrics that represent travel activity and enable service-equivalent comparison.

The project shall establish the baseline mode mix for the incremental ridership or incremental passenger travel, including the baseline modes displaced and their emissions intensities.

The project shall quantify project service emissions attributable to the shifted passenger travel, using appropriate emissions intensities for the eligible public transport service(s).

The project shall implement monitoring capable of attributing incremental ridership or passenger travel to the project intervention(s) using auditable evidence, and capable of preventing double counting between multiple interventions or programs.

2.5 Treatment of service quality and equivalence

The project shall demonstrate that the credited outcome is mode shift rather than reduced mobility. Service equivalence shall be ensured by quantifying travel activity on a passenger travel basis and by applying baseline and project emissions intensities to an equivalent passenger travel unit.

Where the project involves changes in route structure, service frequency, capacity, or fare policy, the project shall document how passenger travel is quantified and how baseline comparability is maintained.

2.6 Boundary attribution and double counting controls

The project shall define the roles of entities involved, including operators, authorities, and any third-party implementers, and shall demonstrate the right to claim emission reductions for the quantified modal shift.

Where the eligible public transport service is also subject to other decarbonisation measures, including electrification, fuel switching, or efficiency improvements, the project shall define how emissions factors are applied and how overlap is prevented. The project shall not claim the same reduction twice through both a lower project emissions factor and an independent credit claim for the fleet decarbonisation measure unless explicitly allowed by PCS and demonstrated to be non-overlapping.

2.7 Applicability evidence requirements

Applicability shall be supported by documentary evidence sufficient for validation. Evidence shall be traceable, dated where relevant, and auditable.

Table 2-1. Minimum applicability evidence (non-exhaustive)

Applicability area	Minimum evidence to be provided
Project description	Intervention description, service area, implementation timeline, implementing entity roles
Service definition	Eligible public transport modes and routes, service capacity and schedules where relevant
Passenger travel metric	Definition of passenger-km or alternative metric, measurement method, QA/QC approach
Baseline mode mix	Evidence supporting displaced modes for incremental ridership, survey design and results where used
Emissions intensities	Baseline mode emissions factors, project service emissions factors and derivation
Attribution approach	Method linking incremental ridership to intervention, controls for trends and confounders
Right to claim	Contracts, operator/authority agreements, non-overlap declarations

Chapter 3 - Conditions for Eligibility

3.1 General eligibility requirement

A project shall be eligible under this methodology only where it is demonstrably within scope, meets all applicability conditions, and can be validated and verified using auditable records. A project shall not proceed to registration where this methodology is not fully applicable or where required evidence cannot be produced in a verifiable form.

3.2 Eligible project activity

The project activity shall consist of an intervention or set of interventions that demonstrably increases passenger travel on eligible public transport services and thereby displaces passenger travel that would otherwise occur using higher-emitting baseline modes.

The project shall identify the eligible public transport service(s) and clearly define the intervention(s) asserted to cause the modal shift. The project shall define the credited population of travel activity and demonstrate that credited reductions arise from mode shift rather than reduced travel.

The project shall not claim emission reductions based on construction, procurement, or policy announcement alone. Crediting is conditional on verified implementation and verified incremental passenger travel attributable to the intervention.

3.3 Eligible public transport services and modes

Eligible services are public transport services that are open to the public or a defined eligible passenger group and are delivered on a scheduled or semi-scheduled basis with measurable passenger travel activity.

Eligible modes may include buses, bus rapid transit, metro, light rail, commuter rail, ferries, and other mass transit services where passenger travel and service emissions can be quantified credibly.

Private charter services, ad hoc services without auditable passenger activity measurement, and services without a credible emissions intensity basis shall be treated as ineligible.

3.4 Incremental passenger travel as the crediting basis

Crediting shall be based on incremental passenger travel attributable to the project intervention(s) during the monitoring period. Incremental passenger travel shall be quantified relative to a defined baseline ridership or passenger travel level that represents the counterfactual absent the project.

The project shall define the baseline ridership or passenger travel level using a credible approach that controls for normal trends, seasonal variation, macroeconomic drivers, and other confounders that could affect ridership independent of the project.

The project shall not assume that all ridership growth is attributable to the intervention. Attribution shall be supported by evidence and shall be conservative.

3.5 Demonstration of displacement of baseline modes

The project shall demonstrate that incremental passenger travel on eligible public transport services displaces travel from identifiable baseline modes. Baseline modes may include private cars, motorcycles, taxis, ride-hailing, informal minibuses, or other modes relevant to the local context.

The project shall establish the baseline mode mix for the incremental passenger travel and shall not assume that all incremental passengers would have used the highest-emitting mode absent the project. Mode mix determination shall be evidence-based and conservative.

Mode shift evidence may include passenger surveys, ticketing data linked to origin-destination patterns, travel demand models, or other approaches acceptable under PCS, provided that the method is auditable and controls for bias. Survey-based evidence shall meet minimum sampling, representativeness, and anti-gaming requirements as specified in the monitoring chapter.

Where displacement cannot be demonstrated credibly, the project shall apply conservative default mode shares that do not inflate reductions or shall exclude the affected incremental passenger travel from crediting.

3.6 Induced demand and rebound exclusion

The project shall assess induced demand risk. Crediting shall exclude passenger travel that represents primarily new trips that would not have occurred absent the project, unless PCS permits inclusion with a conservative treatment and the project can quantify net reductions credibly.

Where induced demand cannot be quantified credibly and is plausibly material, the project shall apply conservative deductions or crediting limits to prevent over-crediting.

3.7 Legal compliance and permits

The project shall comply with all applicable laws and regulations relevant to public transport operation, route licensing, safety, fare collection, accessibility, and infrastructure development.

The project proponent shall demonstrate that all material permits and approvals required for the eligible service operations and the intervention implementation are obtained and valid at the time of registration.

3.8 Regulatory surplus and mandate exclusion

The project shall not be eligible where the intervention is legally mandated in a manner that would deliver equivalent modal shift outcomes absent the project, including enforceable requirements on service frequency, capacity, fare policy, route licensing, or network expansion that materially drive the same ridership change.

Where policies exist that encourage public transport use through incentives without mandating outcomes, the project shall disclose such policies and demonstrate additionality and non-overlap.

3.9 Right to claim and avoidance of double counting

The project proponent shall demonstrate legal authority and contractual rights to claim emission reductions resulting from the quantified modal shift. The project shall not claim emission reductions that are claimed or used under another crediting program, compliance mechanism, or overlapping attribute claim in a manner that conflicts with PCS requirements.

Where the eligible public transport service is also part of an electrification program or fuel switch project, the project shall demonstrate that claims are not overlapping. The project shall not claim the same reduction through both a lower project emissions factor due to electrification and a separate credit claim for that electrification under another methodology unless explicitly allowed by PCS and demonstrated to be non-overlapping.

3.10 Control of overlapping interventions

Where multiple interventions occur within the same service area, such as fare subsidies, service frequency upgrades, infrastructure changes, and marketing campaigns, the project shall define which interventions are included in the project boundary and how incremental passenger travel is attributed to the project intervention(s) without double counting.

Where attribution between interventions cannot be separated credibly, the project shall apply conservative aggregation and shall avoid claiming full benefits for all interventions simultaneously.

3.11 Start date and prior consideration

The project shall define a clear project start date corresponding to the implementation of the intervention(s) and the start of measurable incremental passenger travel.

Where required by PCS rules, the project proponent shall demonstrate prior consideration of carbon finance through contemporaneous evidence. Absence of credible contemporaneous evidence, where required, shall render the project ineligible.

3.12 Monitoring system eligibility

Eligibility under this methodology is conditional on auditable monitoring. The project shall have a monitoring system capable of producing complete and auditable records for passenger travel activity, incremental passenger travel determination, baseline mode mix determination, project service emissions intensity, and attribution controls.

If monitoring is not feasible at validation for the parameters required by this methodology, the project shall not be eligible for registration under this methodology.

3.13 Material change controls

The project proponent shall disclose any material change that may affect applicability, baseline, additionality, passenger travel quantification, mode mix determination, attribution, monitoring, or quantification. Material changes include changes in service frequency, route structure, capacity, fare policy, ticketing system coverage, fleet technology, fuel type, electricity supply arrangements where applicable, and external policies affecting travel behaviour.

Where a material change occurs, the project proponent shall follow PCS procedures for post-registration changes and shall obtain approval where required prior to claiming credits for the affected period.

3.14 Eligibility evidence requirements

Eligibility shall be supported by documentary evidence sufficient for validation and verification. Evidence shall be traceable, dated where relevant, and auditable.

Table 3-1. Minimum eligibility evidence (non-exhaustive)

Eligibility area	Minimum evidence to be provided
Service definition	Routes and service map, schedules, capacity, fare structure, service change records
Passenger travel data	Ticketing datasets, ridership counts, passenger-km estimation method, QA/QC procedures
Incremental travel basis	Baseline ridership model, baseline period datasets, trend controls
Mode mix evidence	Survey design and results, model outputs, or other acceptable evidence
Attribution evidence	Intervention timeline, control group or counterfactual analysis approach
Emissions intensities	Baseline mode emission factors, project service emissions factors and derivation
Overlap controls	Non-overlap statements, separation from electrification/fuel switch crediting
Compliance	Permits, licensing, safety documentation
Right to claim	Contracts and authorisations among relevant entities

Chapter 4 - Project Boundary

4.1 Boundary principle

The project boundary shall include all emission sources and activity data necessary to quantify, in a complete and conservative manner, the net emission reductions attributable to shifting passenger travel from baseline modes to eligible public transport services. The boundary shall be defined such that baseline and project scenarios are comparable and exclusions do not result in over-crediting through unaccounted service emissions, unverified displacement, or double counting.

The boundary shall be defined around the incremental passenger travel attributable to the project intervention(s), the baseline travel modes displaced by that incremental travel, and the project public transport service emissions attributable to delivering that incremental travel.

4.2 Boundary components

The project boundary shall include the incremental passenger travel attributable to the project in monitoring period expressed in passenger-kilometres or another PCS-accepted passenger travel metric.

The baseline boundary shall include emissions associated with delivering the same incremental passenger travel using baseline modes displaced by the project. Baseline modes shall be identified and their emissions intensities shall be applied to the incremental passenger travel on a service-equivalent basis.

The project boundary shall include emissions associated with delivering the incremental passenger travel on the eligible public transport service(s), expressed as a project emissions intensity per passenger-kilometre and applied to the same incremental passenger travel.

Where the eligible public transport service includes multiple routes, vehicle classes, or fuels, the boundary shall include the relevant service emissions intensity for the routes and services that deliver the incremental passenger travel.

4.3 Included greenhouse gases

Emissions shall include CO₂ and may include CH₄ and N₂O where emission factors include those gases. Emissions shall be expressed in CO₂e using the applicable factors.

4.4 Boundary for baseline displaced modes

Baseline modes displaced by the incremental passenger travel shall be defined and evidenced. Baseline modes may include private cars, motorcycles, taxis, ride-hailing, informal transport, or other relevant modes.

The boundary shall include baseline emissions for the displaced modes only to the extent that displacement is supported by evidence. The project shall not assume that all incremental public transport passengers would have used a single highest-emitting baseline mode absent the project unless this is evidenced and conservative.

Where baseline mode shares are uncertain, conservative mode shares and emissions intensities shall be applied to avoid inflating baseline emissions.

4.5 Boundary for project service emissions

Project emissions shall include emissions from operating the eligible public transport service attributable to delivering the incremental passenger travel. Project emissions may be derived using an emissions intensity per passenger-kilometre for the service.

Where the intervention increases service frequency, capacity, or vehicle kilometres operated, project emissions shall reflect the actual service emissions for the incremental service delivered, not a theoretical average that excludes additional supply emissions.

Where the public transport service is electrified, project emissions shall reflect electricity emissions consistent with PCS rules and shall not double count reductions claimed under another methodology.

4.6 Treatment of induced demand and reduced travel

The project boundary shall exclude travel that represents induced demand where induced demand cannot be quantified conservatively. Where induced demand is plausible and material, the project shall apply conservative treatment as specified in Chapter 8 and Chapter 11.

The boundary shall not credit reductions that arise primarily from reduced travel activity. The project shall quantify incremental passenger travel and apply baseline and project emissions intensities to the same travel unit to ensure service-equivalent comparison.

4.7 Boundary exclusions

Upstream lifecycle emissions from manufacturing of vehicles and infrastructure are excluded.

Emissions associated with construction of public transport infrastructure are excluded.

Emissions associated with passenger access travel, such as walking or cycling to stations, are excluded. Where access travel by motorised modes is plausibly material and attributable to the intervention, the project shall assess whether leakage treatment is required under PCS rules.

4.8 Boundary table

Table 4-1. Boundary sources and inclusion status (public transport modal shift)

Source / sink / flow	Included in baseline scenario	Included in project scenario	Inclusion rationale
Passenger travel activity for the credited shift	Yes	Yes	Same travel unit required for service-equivalent comparison.
Baseline mode emissions for displaced travel	Yes	No	Represents emissions avoided through mode shift.
Public transport service operational emissions	No	Yes	Represents project emissions to deliver the shifted travel.
Additional supply emissions due to higher service	No	Yes	Included where service provision increases to enable shift.
Vehicle and infrastructure manufacturing	No	No	Excluded.
Infrastructure construction	No	No	Excluded.

4.9 Documentation requirements

The project proponent shall document the boundary in a manner sufficient for validation and verification. Documentation shall include the definition of incremental passenger travel, the identification of baseline displaced modes and mode share evidence, the definition and derivation of project service emissions intensity, treatment of service changes and additional supply, controls to prevent overlap with other credit claims, and justification for exclusions.

Failure to demonstrate an unambiguous and conservative boundary definition and auditable attribution of incremental passenger travel shall render the project ineligible for issuance for the affected periods.

Chapter 5 - Baseline Scenario and Baseline Emissions

5.1 Baseline principle

The baseline scenario shall represent the delivery of the same incremental passenger travel that occurs due to the project using baseline transport modes that would have been used in the absence of the project intervention(s). The baseline shall be defined in a transparent, conservative, and verifiable manner and shall not be selected or structured to inflate emission reductions.

Baseline emissions shall be determined on a service-equivalent basis using passenger travel units. The project shall not claim emission reductions driven primarily by reduced travel or by unverified assumptions about which modes are displaced.

5.2 Identification of the baseline scenario

The project shall identify the most plausible baseline modes for the incremental passenger travel attributable to the project. Baseline modes may include private cars, motorcycles, taxis, ride-hailing, informal transport services, or other modes relevant to the local context.

The baseline mode mix for the incremental passenger travel shall be evidence-based and representative of the passenger group affected by the intervention(s), the service area, trip types, and the time period. The project shall not assume displacement of a single high-emitting mode unless it is evidenced and conservative.

Where the intervention targets a specific corridor, passenger group, or service segment, baseline mode mix shall be determined for that segment. Where baseline mode mix varies by time of day, season, or route segment, the project shall apply disaggregation or conservative averaging that does not overstate baseline emissions.

5.3 Determination of incremental passenger travel

The project shall quantify incremental passenger travel attributable to the project intervention(s) in monitoring period , expressed in passenger-kilometres or another PCS-accepted passenger travel metric.

Incremental passenger travel shall be determined relative to a defined baseline ridership or passenger travel level that represents the counterfactual absent the project. The baseline ridership level shall be established using a credible approach that accounts for trends, seasonal patterns, population and economic growth, and other confounders that materially affect ridership independent of the project.

Where the project cannot separate the effects of the intervention from other drivers of ridership change, conservative attribution shall be applied such that the credited incremental passenger travel is not overstated.

5.4 Baseline emissions intensity by mode

Baseline emissions shall be calculated using emissions intensities per passenger-kilometre for each baseline mode displaced by the incremental passenger travel.

Baseline emissions intensity for each mode shall be derived from credible sources and shall reflect the relevant vehicle type, fuel, occupancy, operating conditions, and trip characteristics. Where values are uncertain, conservative assumptions shall be applied that do not inflate baseline emissions.

Where the baseline mode is private car or motorcycle, the project shall use representative emissions per vehicle-kilometre combined with conservative occupancy assumptions to convert to emissions per passenger-kilometre. Occupancy assumptions shall be supported by evidence and selected conservatively.

Where the baseline mode is taxi or ride-hailing, occupancy and deadheading assumptions shall be treated conservatively and shall be evidenced where possible. If deadheading and occupancy cannot be credibly quantified, the project shall apply conservative values or exclude the mode from the baseline mix if doing so is required to prevent inflation.

5.5 Baseline emissions calculation

Baseline emissions for monitoring period shall be calculated by applying baseline mode shares and baseline emissions intensities per passenger-kilometre to the incremental passenger travel in period .

Table 5-1. Baseline emissions equations

Parameter	Equation
Baseline emissions

Where:

is incremental passenger travel attributable to the project in period (passenger-km).

is the baseline mode share for mode applicable to the incremental passenger travel in period .

is baseline emissions intensity of mode (tCO₂e/passenger-km).

Mode shares shall sum to one for the incremental passenger travel segment to which they are applied. Where mode shares are uncertain, the project shall apply conservative mode shares that do not inflate baseline emissions.

5.6 Baseline mode share determination requirements

Mode shares used for baseline shall be derived from a credible and auditable method. Methods may include passenger surveys, travel diaries, ticketing-linked origin-destination inference with stated preference validation, or travel demand modelling with calibration to observed data.

Survey-based approaches shall be designed to minimise bias and gaming. The project shall demonstrate sampling representativeness, adequate sample size, and controls for response manipulation. The survey instrument shall be retained and made available for verification.

Where mode shares are based on models, the model shall be documented, calibrated, and validated against observed data. Model assumptions that materially affect mode shares shall be disclosed and conservative choices shall be applied where uncertainty exists.

Where mode shares cannot be established credibly, the project shall apply PCS-defined conservative default shares if available, or shall apply a conservative baseline assumption that results in lower baseline emissions for the incremental passenger travel.

5.7 Baseline validity, updating, and policy interactions

Baseline parameters shall remain valid only where they continue to represent the plausible baseline for the incremental passenger travel. Where material changes occur that affect baseline mode availability, fuel prices, network structure, land-use patterns, competing transport interventions, or policy constraints, the project shall update baseline assumptions in accordance with PCS requirements and in a manner that avoids over-crediting.

Where enforceable policies mandate modal shift outcomes, congestion charging, parking restrictions, or other measures that would produce equivalent modal shift absent the project, the baseline shall be updated conservatively and the project shall not credit reductions that would occur due to mandated changes.

5.8 Documentation requirements

The project proponent shall document baseline scenario identification, baseline ridership level determination and representativeness assessment, incremental passenger travel calculation, mode share determination method and datasets, emissions intensity sources and conversions, occupancy assumptions and supporting evidence, and any baseline updates applied. Documentation shall be sufficient for independent replication.

Chapter 6 - Additionality

6.1 Requirement

The project activity shall be additional. The project proponent shall demonstrate that, in the absence of carbon credit revenues, the intervention(s) would not have occurred as implemented, would not have occurred at the same scale and timing, or would not have delivered the same verified incremental passenger travel and mode shift outcomes.

Additionality shall be assessed at validation. Where PCS requires reassessment at renewal or where material changes occur that affect the additionality basis, additionality shall be reassessed in accordance with PCS procedures.

6.2 Regulatory surplus and mandate test

The project shall not be eligible where the intervention is legally mandated in a manner that would deliver equivalent modal shift outcomes absent the project, including enforceable requirements on service expansion, frequency, fare policy, integrated ticketing, infrastructure upgrades, or network development that materially drive the same ridership change.

Where policies exist that encourage public transport improvements or use through incentives, targets, or non-binding commitments, the project proponent shall disclose those policies and demonstrate that the project is not simply business-as-usual and that carbon revenue is decisive to implementation as implemented.

Where a legally binding mandate comes into force during the crediting period that requires equivalent interventions or outcomes, the project shall not claim emission reductions for impacts that would occur due to the mandate, and baseline and crediting shall be updated conservatively in accordance with PCS requirements.

6.3 Investment analysis or barrier analysis

The project proponent shall demonstrate additionality using either an investment analysis or a barrier analysis, supported by auditable evidence reflecting information available at the time of the decision to implement the project.

6.3.1 Investment analysis

Where investment analysis is applied, the project proponent shall demonstrate that the intervention(s) are not financially attractive without carbon revenues or that carbon revenues are decisive to meeting an investment threshold required by decision-makers.

The analysis shall include all material costs and revenues for the intervention(s), including capex for infrastructure and systems, opex for additional service provision, staffing, maintenance, ticketing system costs, enforcement and demand management costs where applicable, and any impacts on fare revenues.

The analysis shall include all material support mechanisms, including government budgets, grants, subsidies, concessional finance, advertising revenues, land value capture revenues, development finance, and any donor funding. The analysis shall not omit material funding sources.

Sensitivity analysis shall be conducted for material parameters such as ridership, fare revenues, operating costs, fuel or electricity costs, and subsidy levels. Assumptions shall be conservative so that the role of carbon revenue is not overstated.

6.3.2 Barrier analysis

Where barrier analysis is applied, the project proponent shall demonstrate the presence of at least one credible barrier that would prevent implementation of the intervention(s) at the stated scale and timing in the absence of carbon revenues and that the project overcomes the identified barrier(s).

Barrier claims may include limited access to finance for service expansion, inability to sustain operating subsidies for increased frequency, institutional barriers to integrated ticketing, lack of political feasibility for demand management measures without compensatory improvements, technology implementation barriers for ticketing or data systems, or market acceptance barriers for new services. Claims shall be project- and corridor-specific, evidenced, and causally linked to the implementation decision.

Generic claims that public transport is underfunded without evidence shall not be accepted.

6.4 Common practice assessment

The project proponent shall assess whether similar modal shift interventions are common practice in the applicable context, considering geography, corridor characteristics, governance and funding environment, and intervention type.

If similar interventions are already widely implemented without carbon finance and are delivering comparable ridership shifts in the same context, the project shall not be eligible unless the project proponent demonstrates material differences that affect likelihood of implementation and are not driven by legal requirements or normal sector development.

Common practice assessment shall be specific to the intervention type. A city with common practice of minor route adjustments does not imply common practice of integrated fare systems or BRT-grade corridor upgrades.

6.5 Additionality and attribution integrity

Additionality is not satisfied if the credited outcome is primarily due to external factors not caused by the intervention(s), such as fuel price shocks, unrelated policy changes, major land-use changes, unrelated economic shifts, or concurrent transport interventions that are not within the project boundary.

The project shall disclose concurrent interventions and assess confounding effects. Where confounding effects are material and cannot be separated credibly, conservative attribution shall be applied or the project shall not be eligible for crediting for the affected period.

6.6 Timing integrity and prior consideration

Where required by PCS rules, the project proponent shall demonstrate prior consideration of carbon finance through contemporaneous evidence. Absence of credible contemporaneous evidence, where required, shall render the project ineligible.

Where the intervention(s) began prior to entering PCS, the project proponent shall demonstrate eligibility under PCS rules applicable to start date and prior consideration and shall not claim reductions for periods that do not meet PCS timing requirements.

6.7 Additionality failure conditions

A project shall be deemed not additional where interventions are legally mandated, where investment analysis demonstrates financial attractiveness without carbon revenues and the project cannot show carbon revenue is decisive, where grants and subsidies already cover the incremental costs and remove the additionality barrier, where claimed barriers are not supported by corridor-specific evidence, where interventions are common practice without credible differentiation, or where timing and prior consideration requirements are not met.

6.8 Documentation requirements

The project proponent shall provide documentation sufficient for validation. Documentation shall include the regulatory analysis, the selected additionality demonstration method and supporting evidence, common practice evidence and analysis, disclosure of grants, subsidies, concessional finance, and other support mechanisms, disclosure of concurrent interventions and confounding drivers, and any prior consideration evidence required by PCS rules. Documentation shall be traceable, dated where relevant, and auditable.

Chapter 7 - Project Emissions and/or Removals

7.1 Principle

Project emissions shall include all GHG emissions within the project boundary that are attributable to delivering the incremental passenger travel on eligible public transport services during the monitoring period.

This methodology does not quantify removals. No removals shall be claimed under PCS-TR-013.

Project emissions shall be quantified on a service-equivalent basis using passenger-kilometres. Where the intervention increases service supply, project emissions shall reflect the additional operational emissions required to deliver the incremental passenger travel and any additional service output necessary to enable the shift.

7.2 Definition of project service emissions intensity

Project emissions shall be quantified using a project service emissions intensity expressed per passenger-kilometre for the eligible public transport service(s).

Project emissions intensity shall reflect the actual fleet and operational energy use applicable to the routes and services delivering the incremental passenger travel. Project emissions intensity shall account for vehicle fuel or electricity use and shall include the effect of occupancy and load factors on emissions per passenger-kilometre.

Where services are delivered using multiple fuels or vehicle types, project emissions intensity shall be determined as a weighted average based on measured energy use and service output or through disaggregated intensities by service segment.

7.3 Project energy consumption and emission factors

Project emissions may be calculated using either a direct energy consumption approach or an emissions intensity approach, provided that the approach is auditable and conservative.

Where energy consumption can be monitored credibly, the project shall quantify fuel and electricity consumption attributable to the service and allocate it to the incremental passenger travel conservatively.

Where energy consumption cannot be monitored directly at the service level, the project may use conservative default energy intensity values for the service, provided that these values are representative and verifiable and do not understate project emissions.

Fuel emission factors shall be selected from credible and applicable sources consistent with PCS requirements.

Electricity emission factors shall be selected for the electricity system from which the service electricity is drawn in the monitoring period and shall be applied consistently with PCS rules, including treatment of renewable electricity claims and non-overlap controls.

7.4 Treatment of additional service supply

Where the intervention increases service frequency, vehicle-kilometres, or capacity, project emissions shall include emissions from the additional service supplied.

The project shall not claim the full baseline emissions avoided for incremental passengers unless it also accounts for the operational emissions required to provide the additional service that enables those passengers to shift.

Where incremental ridership occurs without additional service supply, project emissions shall still reflect the emissions intensity of the service for the incremental passenger-kilometres delivered.

7.5 Project emissions calculation

Project emissions for monitoring period shall be calculated by applying the project emissions intensity to the incremental passenger travel attributable to the project in period , or by calculating emissions from energy consumption attributable to delivering that incremental passenger travel.

Table 7-1. Project emissions equations

Basis	Project emissions for monitoring period
Intensity-based
Energy-based

Where:

is incremental passenger travel attributable to the project in period (passenger-km).

is project emissions intensity for the eligible public transport service (tCO₂e/passenger-km).

is fuel consumption of fuel attributable to delivering the incremental passenger travel in period .

is the emission factor for fuel (tCO₂e/unit).

is electricity consumption attributable to delivering the incremental passenger travel in period (MWh).

is the electricity emission factor for the relevant system and period (tCO₂e/MWh).

Where the intensity-based approach is used, the project shall document derivation of including energy use basis, occupancy basis, and unit conversions.

7.6 Treatment of occupancy and passenger-km estimation

Project emissions intensity per passenger-kilometre depends on occupancy. Passenger-kilometre estimation shall be conservative and based on auditable data. Where passenger counts are estimated, methods shall be documented and bias controlled.

Where the project uses passenger counts and route distances to estimate passenger-kilometres, the project shall document the estimation method, data sources, and QA/QC controls. Where load factors vary materially by time and route, disaggregation shall be applied or conservative assumptions shall be used.

The project shall not use optimistic occupancy assumptions that reduce project emissions intensity.

7.7 Excluded project emissions

Upstream lifecycle emissions from manufacturing of vehicles and infrastructure are excluded.

Emissions associated with construction of infrastructure are excluded.

Emissions from ancillary activities not attributable to delivering the incremental passenger travel, such as general administrative electricity use, are excluded unless PCS requires inclusion due to materiality and attribution.

7.8 Documentation requirements

The project proponent shall document the derivation of incremental passenger travel, the determination of project service emissions intensity or energy consumption attributable to the service, emission factor sources and versions, occupancy and passenger-kilometre estimation methods, treatment of additional service supply, and calculation procedures. Documentation shall include operational datasets, ticketing and ridership datasets, fuel and electricity records, and calculation files sufficient for independent replication.

Chapter 8 - Leakage

8.1 Principle

Leakage is an increase in GHG emissions that occurs outside the project boundary and is attributable to implementation of the project activity. Leakage shall be assessed and included in the net emission reduction calculation where it is measurable, attributable, and material.

For modal shift projects, leakage risk is mainly associated with induced demand and rebound effects, displacement of low-emission modes, shifts in road traffic that offset reductions, and overlap with other interventions and claims that result in double counting.

8.2 Leakage assessment requirement

The project proponent shall assess leakage based on the intervention type, service area, baseline mode mix, and system context. Leakage assessment is mandatory.

Where leakage sources are plausible and material, leakage shall be quantified conservatively and deducted from emission reductions. Where leakage cannot be quantified credibly and the risk is material, the project shall apply conservative deductions up to and including exclusion of affected incremental passenger travel from issuance for the monitoring period.

8.3 Induced demand and rebound leakage

Induced demand leakage occurs where the intervention leads to additional passenger travel that would not have occurred absent the project rather than displacing baseline modes. This may occur due to lower fares, improved accessibility, improved convenience, or changes in travel patterns.

Where induced demand is plausible and material, the project shall quantify the induced travel share and exclude or deduct it from credited incremental passenger travel. Where induced demand cannot be quantified credibly, the project shall apply conservative limits on credited incremental passenger travel.

Rebound leakage may occur where reduced road congestion due to mode shift frees capacity and induces additional road traffic by other users. Where this effect is plausibly material in the service area and cannot be ignored, the project shall assess and treat it conservatively in accordance with PCS requirements.

8.4 Mode shift from low-emission modes

Leakage occurs where incremental public transport ridership is driven primarily by passengers shifting from already low-emission modes such as walking or cycling. Where such shifts are plausible and material, the project shall quantify the share of incremental passenger travel originating from low-emission modes and exclude or deduct it from credited travel.

Where the baseline mode mix evidence indicates significant shares from walking, cycling, or other low-emission modes, those shares shall be applied in baseline mode mix and will reduce baseline emissions accordingly. Where baseline mode mix is uncertain, the project shall apply conservative shares for low-emission modes to avoid over-crediting.

8.5 Shifting of baseline high-emission activity outside the boundary

Leakage may occur where the intervention displaces high-emission travel from one corridor to another or causes traffic diversion that offsets emissions reductions.

Where corridor-specific interventions are implemented and traffic diversion is plausible, the project shall assess whether diverted traffic materially affects net emissions and shall apply conservative deductions where required.

8.6 Overlap and double counting leakage

Leakage risk arises where the eligible public transport service is simultaneously subject to electrification, fuel switch, or efficiency upgrade measures claimed under other crediting activities.

The project shall demonstrate non-overlap of claims. Where the fleet emissions intensity is reduced due to a measure credited under another methodology, the project shall not claim that same reduction again through a reduced project emissions intensity unless explicitly allowed by PCS and demonstrated to be non-overlapping.

Where fare subsidies, congestion policies, or other external interventions materially drive ridership changes during the monitoring period and are not within the project boundary, the project shall treat attribution conservatively and adjust credited incremental passenger travel downward.

8.7 Leakage quantification

Where quantified, leakage emissions for monitoring period shall be calculated and deducted from emission reductions.

Table 8-1. Leakage accounting structure

Leakage component	Leakage emissions for monitoring period
Induced demand / rebound
Shift from low-emission modes	Treated through baseline mode shares or exclusion
Corridor diversion effects
Overlap/double counting effects	Treated through exclusions or PCS-defined deduction
Total leakage

Leakage may be treated through quantified deductions where credible, or through conservative exclusions or crediting limits where quantification is not feasible.

8.8 Documentation requirements

The project proponent shall document leakage assessment, inclusion or exclusion rationale, evidence supporting induced demand and rebound assessment, baseline mode mix evidence including shares from low-emission modes, any corridor diversion assessment performed, documentation of concurrent interventions and overlap controls, and any leakage calculations performed. Evidence shall be sufficient to allow validation and verification of leakage conclusions.

Chapter 9 - Net GHG Impact and Crediting

9.1 Principle

Emission reductions credited under this methodology shall be calculated for each monitoring period as the net difference between baseline emissions and the sum of project emissions and leakage emissions. Crediting shall be based on monitored and verifiable data and shall be limited to incremental passenger travel attributable to the project intervention(s) for which baseline mode shares and project service emissions can be quantified credibly.

Crediting shall not be issued for speculative attribution. Crediting shall not be issued where incremental passenger travel cannot be quantified and defended or where baseline displaced modes are not evidenced.

9.2 Net emission reductions

Net emission reductions for monitoring period shall be calculated as follows.

Table 9-1. Net emission reduction equation

Parameter	Equation
Net emission reductions

Where:

is emission reductions in monitoring period (tCO₂e).

is baseline emissions in monitoring period (tCO₂e), determined in Chapter 5 from displaced mode shares and emissions intensities applied to incremental passenger travel.

is project emissions in monitoring period (tCO₂e), determined in Chapter 7 from public transport service emissions attributable to delivering incremental passenger travel.

is leakage emissions in monitoring period (tCO₂e), determined in Chapter 8.

9.3 Credited activity and issuance boundary

Crediting is restricted to incremental passenger travel attributable to the intervention(s) during the monitoring period.

Incremental passenger travel shall be expressed in passenger-kilometres or other PCS-accepted passenger travel metrics. Where passenger-kilometres are estimated rather than directly measured, estimation shall be conservative and supported by auditable data.

The project shall not credit ridership growth that is not attributable to the intervention(s) or that is driven primarily by confounding drivers not within the project boundary.

9.4 Mode share application and conservativeness

Baseline mode shares applied to incremental passenger travel shall be evidence-based and conservative. Where mode shares are derived from surveys or models, the project shall apply controls that prevent selection bias and gaming.

Where baseline mode share evidence is weak or uncertain, the project shall apply conservative mode shares that do not inflate baseline emissions. Where conservative mode shares cannot be established credibly, the project shall exclude affected incremental passenger travel from crediting.

9.5 Treatment of induced demand and low-emission mode shift

Where induced demand is identified, the project shall exclude induced travel from credited incremental passenger travel or apply conservative leakage deductions in accordance with Chapter 8.

Where incremental ridership is sourced from low-emission modes such as walking and cycling, baseline mode shares shall include those modes, which reduces baseline emissions and therefore reduces credited reductions. The project shall not exclude low-emission modes from the baseline mode mix unless evidenced.

9.6 Treatment of project service changes

Where the intervention increases service supply, project emissions shall include emissions associated with the additional service and shall be reflected in the emissions intensity or energy-based accounting approach.

Where service supply changes materially during the monitoring period, the project shall update project emissions intensity accordingly or disaggregate calculations by period or service segment to maintain accuracy and conservativeness.

9.7 Treatment of negative or zero results

Emission reductions shall not be claimed for periods in which . Where is negative, it shall be reported and shall not be carried forward to offset positive emission reductions in other monitoring periods.

9.8 Rounding and units

All quantities shall be expressed in consistent units with documented conversion factors. Emissions and emission reductions shall be expressed in tCO₂e.

Rounding shall be applied conservatively. Where rounding is required, values shall be rounded down to the nearest whole unit at the stage of credit issuance. Intermediate calculations shall retain sufficient decimal precision to avoid systematic inflation of results.

9.9 Crediting period and renewal

The crediting period length, renewal rules, and any limits on total crediting duration shall be applied in accordance with PCS requirements. At renewal or where required by PCS, the project shall reassess baseline mode shares and emissions intensities, project service emissions intensity, induced demand and rebound risks, and policy or system changes that affect baseline and attribution.

9.10 Documentation requirements

For each monitoring period, the project proponent shall provide a complete calculation record that includes the intervention implementation evidence, incremental passenger travel totals and methodology, baseline ridership counterfactual model and datasets, baseline mode share evidence, baseline mode emissions factors and occupancy assumptions, project service emissions intensity or energy consumption basis and emission factors, leakage assessment and any leakage deductions applied, data QA/QC and data gaps, and the full calculation of net emission reductions. Records shall be sufficient to support validation and verification and allow independent reproduction of results.

Chapter 10 - Monitoring Requirements

10.1 Objective

The objective of monitoring under this methodology is to produce complete, accurate, and auditable data sufficient to quantify baseline emissions, project emissions, leakage where applicable, and net emission reductions for each monitoring period. Monitoring shall enable independent verification of intervention implementation, incremental passenger travel attributable to the intervention(s), baseline mode shares for the incremental passenger travel, project service emissions attributable to delivering that incremental travel, and integrity controls that prevent over-crediting.

Monitoring shall be implemented as a system. The system shall include passenger activity measurement procedures, counterfactual ridership determination procedures, mode share measurement procedures, public transport service emissions data procedures, QA/QC controls, change control, and record retention practices.

10.2 Monitoring period

The project proponent shall define monitoring periods in accordance with PCS requirements. For each monitoring period, the project shall compile monitored data and supporting evidence that cover the full period without gaps. Where data gaps occur, conservative treatment shall be applied as set out in this chapter.

10.3 Parameters to be monitored

The project proponent shall monitor the parameters in Table 10-1, as applicable to the project configuration and quantification approach. Where a parameter is not applicable, the project proponent shall justify non-applicability and demonstrate that exclusion does not result in over-crediting.

Table 10-1. Monitoring parameters (minimum)

Parameter	Description	Unit	Applicable to	Monitoring frequency	Data source / method	QA/QC requirements
Intervention implementation evidence	Evidence that interventions were implemented	N/A	All projects	On implementation; update on change	Contracts, commissioning reports, service change logs	Document control; dated evidence
Ticketing/ridership data	Passenger boardings and journeys	passenger counts	Most projects	Continuous; aggregated per period	AFC systems, ticket sales, gate counts	Completeness checks; anomaly checks
	Incremental passenger travel attributable to project	passenger-km	All projects	Per period	Counterfactual model + observed data	Conservative attribution
Passenger-km estimation inputs	Distances, OD matrices, trip lengths	km	Conditional	Per period	Route data, OD inference, surveys	Bias controls; validation
Baseline ridership counterfactual	Baseline passenger travel absent project	passenger-km	All projects	Per period	Baseline model, baseline period datasets	Trend/seasonality controls
Baseline mode shares	Mode mix for incremental travel	%	All projects	As required	Surveys, models, OD + survey validation	Representativeness; anti-gaming
Baseline mode emissions intensities	Emissions per passenger-km by mode	tCO₂e/passenger-km	All projects	Update as required	Credible sources	Version control; applicability checks
Project service emissions data	Fuel/electricity use and/or emissions intensity	fuel/MWh or tCO₂e/pkm	All projects	Per period	Operator energy records, fleet records	Reconciliation to service output
Project emissions intensity	Public transport emissions per passenger-km	tCO₂e/passenger-km	All projects	Per period	Derived from energy use + passenger-km	Conservative occupancy treatment
Leakage indicators	Induced demand, diversion, overlap	N/A	Conditional	Per period	Surveys, traffic data, program records	Conservative treatment
Data gaps log	Missing data and treatments	N/A	All projects	Per period	QA/QC record	Conservative rule application

10.4 Intervention implementation monitoring

The project shall maintain dated and auditable evidence that the intervention(s) were implemented as described, including commissioning records for infrastructure, service change logs for frequency or route changes, fare policy implementation records, and any operational documentation relevant to the intervention.

Where implementation differs materially from the validated design, the project shall disclose the change and apply PCS change control procedures. Credits shall not be issued for impacts that cannot be attributed credibly to implemented interventions.

10.5 Passenger travel measurement

Passenger travel shall be monitored using auditable systems. Where automated fare collection systems are used, the project shall retain raw extracts and document data processing steps.

Where passenger counts are collected through manual counts, the project shall document sampling design, counting procedures, training, and QA/QC measures.

Passenger-kilometres shall be derived using a documented method appropriate to the available data. The method shall avoid optimistic assumptions about trip lengths, transfers, or completeness of ticketing coverage.

Where passenger-kilometres are estimated using average trip length, the average trip length shall be supported by representative data and shall be updated where conditions change.

10.6 Determination of incremental passenger travel

Incremental passenger travel shall be determined for each monitoring period by comparing observed passenger travel to a counterfactual baseline passenger travel level that represents the expected passenger travel absent the project intervention(s).

The counterfactual baseline shall account for seasonality and normal trends. Where baseline travel is affected by external shocks, the project shall treat attribution conservatively and shall not credit short-term ridership changes driven by unrelated confounding factors.

Where multiple interventions occur in the same period and attribution cannot be separated, the project shall apply conservative aggregation and shall not attribute full incremental travel to the PCS project unless evidenced.

10.7 Mode share monitoring for baseline displaced modes

Baseline mode shares for incremental passenger travel shall be established using an evidence-based approach suitable for verification.

Where passenger surveys are used, the survey shall measure the previous mode that would have been used for the same trip absent the intervention. The survey design shall address selection bias, leading questions, and response manipulation.

Survey sampling shall be representative of the incremental passenger population by route, time, and passenger type. Sample size shall be sufficient for materiality. Survey data collection shall be documented and independently auditable.

Where mode shares are based on models, the model shall be documented, calibrated, and validated against observed data. The project shall retain model inputs, calibration outputs, and sensitivity results.

Mode share updates shall be conducted when interventions, service conditions, fares, or competing mode conditions change materially.

10.8 Project service emissions monitoring

Project service emissions shall be monitored using operator energy consumption records and service output data sufficient to derive emissions per passenger-kilometre.

Where fuel consumption is monitored, the project shall retain fuel purchase and dispensing records and reconcile them with vehicle-kilometres operated and service schedules.

Where electricity consumption applies, the project shall retain electricity consumption and emission factor records consistent with PCS rules and disaggregate by electricity system where applicable.

The project shall apply conservative occupancy and passenger-kilometre estimation such that project emissions intensity is not understated.

Where the intervention increases service supply, the project shall monitor additional vehicle-kilometres operated and associated energy consumption so that additional supply emissions are included.

10.9 QA/QC and internal controls

Monitoring data shall be subject to QA/QC controls sufficient to ensure accuracy and integrity. The project shall implement documented procedures for data collection, processing, review, and change control, including an auditable trail from raw records to reported totals.

The project shall implement internal consistency checks including reconciliation of passenger counts between ticketing systems and independent counts where available, plausibility checks of passenger-kilometres versus capacity and schedules, reconciliation of energy consumption versus vehicle-kilometres operated, and review of mode share survey results for bias and consistency.

10.10 Data gaps and conservative treatment

Where monitored data are missing, corrupted, or otherwise unavailable, the project proponent shall apply a conservative approach to gap-filling that does not increase credited reductions.

Where passenger travel data are missing, the default treatment is exclusion of the affected period from crediting unless conservative reconstruction is possible using independent auditable records.

Where mode share data are missing or outdated and conditions changed materially, the project shall apply conservative mode shares that reduce baseline emissions or exclude affected incremental travel from crediting.

Where service emissions data are missing, the project shall apply conservative emissions intensity values that do not understate project emissions or exclude affected periods.

All data gaps and treatments shall be documented with the period affected and the impact on results.

Where credible conservative quantification cannot be demonstrated for a period, the project shall apply conservative deductions up to and including zero issuance for the affected monitoring period.

10.11 Record retention and accessibility

The project proponent shall retain monitoring records and supporting evidence for a period consistent with PCS requirements and sufficient to allow validation and verification across the crediting period and subsequent audits.

Records shall be stored to prevent loss and unauthorised modification and shall be made available to the VVB and PCS upon request.

10.12 Monitoring report content

For each monitoring period, the project proponent shall prepare a monitoring report that includes the monitoring period definition and operational summary, intervention implementation status, observed passenger travel and datasets, baseline counterfactual approach and datasets, incremental passenger travel results, mode share evidence and results, baseline emissions factors and occupancy assumptions, project service emissions data and emission factor sources, leakage assessment and any leakage deductions applied, data QA/QC and data gaps, and the full calculation of net emission reductions.

Chapter 11 - Uncertainty and Conservativeness

11.1 Principle

Uncertainty shall be managed to protect environmental integrity. Where uncertainty affects the quantification of emission reductions, the project proponent shall apply conservative approaches that avoid over-crediting.

Uncertainty treatment shall be transparent, documented, and verifiable. Weak data shall not be compensated by favourable assumptions.

11.2 Identification of uncertainty sources

The project proponent shall identify and document the sources of uncertainty that may materially affect baseline emissions, project emissions, leakage, and net emission reductions.

For modal shift projects, uncertainty commonly arises from inaccurate passenger travel measurement, incomplete ticketing coverage, passenger-kilometre estimation uncertainty, weak counterfactual baseline ridership determination, confounding drivers not controlled in attribution, biased mode share surveys, survey gaming risk, model uncertainty in mode shares, uncertainty in baseline mode emissions intensities and occupancy assumptions, uncertainty in project service emissions intensity and occupancy assumptions, uncertainty in induced demand and rebound impacts, and overlap risks with other interventions and claims.

Only uncertainty sources that affect the quantified net difference between baseline and project outcomes shall be considered for conservative treatment under this methodology.

11.3 Uncertainty in incremental passenger travel attribution

Incremental passenger travel is a gating integrity condition. Where cannot be quantified credibly and attributed to the project intervention(s), the affected travel shall not be credited.

Where counterfactual baseline ridership is uncertain due to confounding drivers or weak baseline models, conservative attribution shall be applied. The project shall not credit ridership changes driven by unrelated external shocks such as fuel price changes, unrelated policy changes, major land-use shifts, or macroeconomic events unless the project can isolate the intervention effect credibly.

Where multiple concurrent interventions affect ridership and attribution cannot be separated, conservative attribution shall be applied or credited incremental passenger travel shall be capped to the portion that can be defended.

11.4 Passenger-kilometre estimation uncertainty

Where passenger-kilometres are estimated rather than directly measured, assumptions regarding trip lengths, transfers, and origin-destination patterns create uncertainty.

The project shall apply conservative passenger-kilometre estimation methods that do not overstate incremental passenger travel. Where average trip length is used, the project shall use representative data and apply conservative adjustments where uncertainty is material.

Where estimation assumptions materially affect results and cannot be validated, conservative reductions shall be applied to incremental passenger travel or the affected segment shall be excluded.

11.5 Mode share uncertainty

Baseline mode shares for incremental passenger travel materially affect baseline emissions. Where mode shares are uncertain, the project shall apply conservative mode shares that do not inflate baseline emissions.

Where surveys are used, uncertainty arises from selection bias, response bias, small sample sizes, and gaming risk. If survey quality is weak or representativeness cannot be demonstrated, the project shall not use the survey results as the basis for high-emitting displacement claims. The project shall apply conservative mode shares that increase the share of low-emission modes and decrease the share of high-emitting modes unless contrary evidence is strong and auditable.

Where mode shares are model-based, uncertainty arises from model assumptions and calibration. If model validation is weak or inputs are uncertain, conservative mode shares shall be applied.

Where mode share evidence is missing for a monitoring period and conditions changed materially, the project shall apply conservative mode shares or exclude affected incremental travel.

11.6 Baseline emissions intensity uncertainty

Baseline emissions intensities per passenger-kilometre depend on vehicle fuel economy, occupancy, and operating conditions. Where baseline emissions intensity values are uncertain, the project shall apply conservative assumptions that do not inflate baseline emissions.

For private car and motorcycle baselines, conservative occupancy assumptions shall be applied. The project shall not assume low occupancy if it increases baseline emissions unless supported by robust evidence.

For taxi and ride-hailing baselines, deadheading and occupancy assumptions shall be treated conservatively. Where these parameters cannot be evidenced, conservative baseline emissions intensities shall be applied that do not inflate baseline emissions.

11.7 Project emissions intensity uncertainty

Project service emissions depend on energy use and passenger-kilometres. Where service emissions data are uncertain or incomplete, the project shall apply conservative assumptions that do not understate project emissions.

Where energy consumption data are incomplete, the project shall apply conservative higher emissions intensities or exclude the affected period or segment.

Where occupancy assumptions affect project emissions intensity, the project shall not use optimistic occupancy assumptions that reduce project emissions per passenger-kilometre without evidence.

Where additional service supply is required to enable the shift and is not measured, the project shall treat uncertainty conservatively by assigning higher project emissions or by limiting credited incremental travel.

11.8 Induced demand and rebound uncertainty

Induced demand and rebound can materially reduce net benefits. Where induced demand and rebound are plausible and cannot be quantified credibly, conservative crediting limits or conservative deductions shall be applied.

Where mode share evidence indicates significant shares from walking, cycling, or other low-emission modes, those shares shall be included. Where uncertainty exists, conservative assumptions shall increase low-emission shares.

11.9 Overlap and double counting uncertainty

Where other interventions reduce public transport service emissions intensity, such as electrification or fuel switching credited elsewhere, uncertainty arises if the modal shift project applies a reduced project emissions factor. The project shall treat overlap conservatively by applying emission factors that avoid double counting or by excluding overlapping reductions unless explicitly allowed and evidenced.

Where external policies drive ridership and cannot be separated, attribution shall be treated conservatively.

11.10 Data gaps and estimation

Data gaps increase uncertainty. Gap-filling shall not increase credited reductions.

Where passenger travel data are missing, the default treatment is exclusion of the affected period from crediting unless conservative reconstruction is possible using independent auditable records.

Where mode share data are missing or invalid, the default treatment is application of conservative mode shares that reduce baseline emissions or exclusion of affected incremental travel.

Where service emissions data are missing, the default treatment is application of conservative higher emissions intensities or exclusion of the affected period.

All data gaps and treatments shall be documented with the period affected and the impact on results.

Where credible conservative quantification cannot be demonstrated for a period, the project shall apply conservative deductions up to and including zero issuance for the affected monitoring period.

11.11 Documentation requirements

The project proponent shall maintain documentation sufficient for validation and verification. Documentation shall include intervention implementation records, ticketing and passenger datasets and QA/QC records, passenger-kilometre estimation methods and inputs, counterfactual baseline ridership determination and datasets, mode share survey instruments and datasets and representativeness evidence, mode share models and validation evidence where applicable, baseline emissions factors and occupancy assumptions, project service energy and emissions datasets and emission factor sources, records of additional service supply and energy use, leakage assessment evidence for induced demand, rebound, and diversion, overlap control documentation, and records of data gaps and conservative treatments applied.

Chapter 12 - Validation and Verification Guidance

12.1 Objective

This chapter defines the minimum validation and verification checks that shall be applied by the Validation and Verification Body (VVB) to determine whether the project is eligible, correctly applies this methodology, and has quantified emission reductions in a complete and conservative manner.

Where the VVB identifies non-conformities that materially affect eligibility, incremental passenger travel attribution, baseline mode mix credibility, project service emissions accounting, leakage treatment, emission factor applicability, overlap control, or quantification results, the VVB shall not issue a positive opinion for registration or issuance unless the non-conformities are corrected and corrective evidence is provided.

12.2 Validation scope

At validation, the VVB shall confirm that the project meets eligibility and applicability conditions and that the project design and monitoring system can implement this methodology as written. The VVB shall assess whether the eligible service definition and passenger travel metric are appropriate and auditable, whether the project intervention(s) are clearly defined and implemented within the boundary, whether the counterfactual baseline ridership determination approach is credible, whether baseline displaced modes and mode shares can be established in a conservative and auditable manner, whether baseline and project emissions intensities are correctly defined, whether additional service supply emissions are included where relevant, whether double counting risks are managed, and whether the project proponent has the right to claim emission reductions.

12.3 Validation checks on eligibility and applicability

The VVB shall confirm that the project is within scope and that exclusion triggers do not apply. The VVB shall verify legal compliance and required permits for the eligible service operations and intervention implementation.

The VVB shall verify the project start date and assess prior consideration requirements where applicable. The VVB shall assess the project proponent’s right to claim emission reductions and evaluate overlap risks with other crediting schemes, compliance instruments, and corporate claims.

The VVB shall assess whether the intervention is legally mandated in a manner that would deliver equivalent ridership and mode shift outcomes absent the project.

12.4 Validation checks on boundary definition and overlap controls

The VVB shall assess whether the project boundary captures incremental passenger travel attributable to the intervention(s), baseline displaced modes for that incremental travel, and project service emissions attributable to delivering that incremental travel.

The VVB shall assess overlap controls where the eligible public transport service is also subject to electrification, fuel switching, or efficiency upgrades credited elsewhere. The VVB shall confirm that the project does not double claim reductions through both modal shift crediting and fleet decarbonisation crediting unless explicitly allowed and demonstrated to be non-overlapping.

Where multiple interventions occur in the same service area, the VVB shall assess whether the project has credible attribution controls and conservative aggregation where separation is not feasible.

12.5 Validation checks on incremental passenger travel and counterfactual credibility

The VVB shall assess the method for determining incremental passenger travel and the counterfactual baseline ridership level. The VVB shall verify baseline period selection, trend and seasonality controls, and treatment of confounding drivers.

The VVB shall assess whether the method avoids attributing unrelated ridership growth to the project. Where confounding drivers are material, the VVB shall require conservative attribution or exclusion of affected periods.

Where ridership changes are influenced by external shocks, the VVB shall confirm that attribution is treated conservatively.

12.6 Validation checks on mode share determination

The VVB shall assess the method used to determine baseline displaced mode shares. Where surveys are used, the VVB shall assess survey design, sampling representativeness, sample size, data collection controls, and anti-gaming measures.

The VVB shall assess whether the survey question design accurately captures the previous mode for the same trip absent the intervention. The VVB shall assess whether results are plausible given context and whether selection bias could inflate high-emitting displaced mode shares.

Where models are used, the VVB shall assess model calibration and validation against observed data and assess sensitivity to key assumptions. The VVB shall require conservative mode shares where uncertainty exists.

12.7 Validation checks on baseline and project emissions intensities

The VVB shall verify baseline emissions intensities per passenger-kilometre for each baseline mode, including fuel economy, occupancy assumptions, and unit conversions. The VVB shall confirm that baseline assumptions are representative and conservative.

The VVB shall verify project emissions intensity for the eligible public transport service, including energy consumption data sources, occupancy and passenger-kilometre estimation, and the inclusion of additional service supply emissions where the intervention increases service provision.

Where electricity is used, the VVB shall verify electricity system mapping and emission factor selection consistent with PCS rules.

12.8 Validation checks on additionality

The VVB shall assess the additionality demonstration for completeness and credibility. The VVB shall confirm that the intervention is not legally mandated and assess policy interactions including subsidies, grants, donor funding, and budget allocations.

Where investment analysis is used, the VVB shall assess whether all material funding sources and revenues are included and whether sensitivity analysis is appropriate. Where barrier analysis is used, the VVB shall assess whether barriers are corridor- and intervention-specific and evidenced.

The VVB shall assess the common practice assessment and confirm that the applicable context is appropriate and that conclusions are supported by evidence.

12.9 Verification scope

At verification, the VVB shall confirm that monitoring data and calculations for each monitoring period are complete, accurate, and traceable, and that the project remains eligible under this methodology.

The VVB shall verify that service definition, route coverage, fare policy, service frequency and capacity, monitoring systems, and intervention components have not changed in a manner that affects baseline comparability, attribution, project emissions accounting, or quantification without appropriate PCS approval.

12.10 Verification checks on passenger travel data integrity

The VVB shall verify ticketing and ridership datasets and confirm that passenger travel totals are supported by raw records and QA/QC procedures.

The VVB shall verify passenger-kilometre estimation methods and confirm plausibility against capacity, service schedules, and independent counts where available.

Where passenger travel data are incomplete or inconsistent, the VVB shall require conservative exclusions.

12.11 Verification checks on incremental passenger travel attribution

The VVB shall reproduce or check the determination of incremental passenger travel for the monitoring period, including the counterfactual baseline ridership level and trend/seasonality controls.

The VVB shall assess whether confounding drivers are present and whether attribution remains conservative. Where attribution is not defensible, the VVB shall require reduction or exclusion of credited incremental travel.

12.12 Verification checks on mode share updates and validity

The VVB shall verify baseline mode share evidence and confirm that mode share assumptions remain valid for the monitoring period. Where conditions changed materially, the VVB shall verify that mode shares were updated or that conservative treatment was applied.

Where surveys are used, the VVB shall verify survey execution and data integrity for the period. Where models are used, the VVB shall verify input updates and calibration status.

12.13 Verification checks on project service emissions accounting

The VVB shall verify project service energy consumption and emissions intensity for the monitoring period and confirm that additional service supply emissions are included where service provision increased.

The VVB shall verify emission factor sources and versions and confirm correct unit conversions and aggregation.

Where electricity is used, the VVB shall verify electricity emission factor selection and mapping and verify compliance with PCS rules on renewable electricity claims and overlap controls.

12.14 Verification checks on leakage and overlap risks

The VVB shall verify leakage assessment, including induced demand risk, rebound and diversion indicators where applicable, and treatment of low-emission mode shifts in baseline mode shares.

The VVB shall verify overlap controls with other interventions and crediting claims, including electrification and fuel switching of the same service. Where overlap exists, the VVB shall require conservative corrections or exclusions.

12.15 Non-conformities and corrective actions

The VVB shall classify non-conformities based on materiality. Material non-conformities shall be corrected before a positive validation opinion or verification statement is issued.

Where corrections require changes to ridership datasets, passenger-kilometre estimates, counterfactual baselines, mode shares, emissions intensities, leakage deductions, or calculation methods, the VVB shall verify revised materials and confirm that revisions do not introduce over-crediting.

12.16 Common failure conditions under this methodology

A project shall be treated as having a material integrity failure where incremental passenger travel cannot be established, counterfactual baseline ridership is weak or manipulable, baseline mode share surveys are biased or gamed, baseline mode shares are cherry-picked, project service emissions accounting excludes additional supply emissions, service emissions data are incomplete, induced demand is ignored where material, or overlap with other crediting claims is unmanaged.

Where integrity cannot be established for a monitoring period, the VVB shall apply conservative outcomes up to and including zero issuance for the affected period.

12.17 Documentation requirements

The project proponent shall provide the VVB and PCS with all documents and datasets necessary to perform the checks in this chapter. Evidence shall be organised, traceable, and sufficient to support replication of results and independent assessment.

Chapter 13 - References

13.1 General requirement

The project proponent shall use credible, publicly available, and verifiable sources for baseline mode emissions intensities, occupancy assumptions, project service emissions factors or energy intensity, electricity emission factors where applicable, and any leakage assumptions or deductions applied. References shall be sufficiently specific to allow independent replication, including the title, issuing entity, version number or publication date, and the relevant sections or datasets.

Where multiple credible sources exist for a parameter, the project proponent shall justify the selection and shall apply conservative choices where uncertainty exists.

13.2 Minimum reference categories

PCS documents apply, including relevant PCS standards, this methodology, any referenced PCS methodological tools, and applicable PCS templates and forms. Host country laws and regulations apply where they affect public transport operation, route licensing, safety, fare collection, and data protection for passenger surveys and ticketing systems. Authoritative sources on fuel emission factors apply for project service fuel combustion emissions. Official electricity system datasets apply where electricity is used. Recognised technical standards for passenger count systems, survey design integrity, and travel demand modelling apply where used to support monitoring integrity and conservative attribution.

13.3 Citation and recordkeeping requirements

All sources used shall be cited in the project documentation and retained as part of the project record. Where a dataset is updated periodically, the project proponent shall retain the specific version used for each monitoring period and demonstrate consistency with update requirements. Monitoring datasets, survey instruments, and model files used for attribution and mode shares shall be retained with traceability to credited calculations.

Annex A - Parameters and Default Values

A.1 General

This annex specifies the minimum parameters required to implement this methodology. Project proponents shall use measured data where required. Default values may be used only where explicitly allowed and shall be justified as applicable and conservative.

Table A-1. Parameters (minimum)

Parameter	Description	Unit	Applicable to	Data source / method	Monitoring frequency	Default value allowed
	Incremental passenger travel attributable to project	passenger-km	All projects	Ticketing + counterfactual	Per period	No
Baseline ridership counterfactual	Baseline passenger travel absent project	passenger-km	All projects	Baseline model	Per period	No
	Baseline mode share for displaced travel	%	All projects	Survey/model	Update as required	Limited; only if PCS provides defaults
	Baseline emissions intensity by mode	tCO₂e/passenger-km	All projects	Credible sources	Update as required	Yes, where authoritative published factors are used
	Project service emissions intensity	tCO₂e/passenger-km	All projects	Operator data	Per period	Limited; conservative only
	Leakage emissions	tCO₂e	Conditional	Leakage assessment	Per period	No

Annex B - Worked Example

B.1 Example purpose and limitations

This worked example is illustrative and demonstrates calculation logic. Project proponents shall use project-specific monitored data, baseline mode shares and emissions intensities consistent with PCS requirements, project service emissions intensity for the monitored service, and conservative leakage deductions where required.

B.2 Example scenario and inputs

Assume an intervention increases incremental passenger travel on a metro line. Baseline displaced modes are a mix of private car and ride-hailing. Project service emissions are from electricity for metro operations.

Table B-1. Example inputs for monitoring period

Item	Value	Notes
Incremental passenger travel	120,000,000 passenger-km	Verified ticketing + attribution
Baseline mode share: car	70%	Evidence-based
Baseline mode share: ride-hailing	30%	Evidence-based
Baseline EI car	0.00018 tCO₂e/pkm	Example only
Baseline EI ride-hailing	0.00025 tCO₂e/pkm	Example only
Project EI	0.00005 tCO₂e/pkm	Example only
Leakage	1,000 tCO₂e	Example deduction

B.3 Baseline emissions

Compute weighted baseline EI:

B.4 Project emissions

B.5 Net emission reductions

Annex C - Monitoring Data Sheet

C.1 Monitoring log requirements

The project proponent shall maintain a monitoring log that allows independent reproduction of monitoring period totals and linkage to raw records. The monitoring log shall be maintained for each monitoring period and retained with supporting evidence.

Table C-1. Monitoring data sheet (minimum fields)

Field	Description	Unit / format	Required
Monitoring period ID	Unique identifier	Text	Yes
Period start date/time	Start of monitoring period	YYYY-MM-DD hh:mm	Yes
Period end date/time	End of monitoring period	YYYY-MM-DD hh:mm	Yes
Intervention status	Implemented / changed	Text	Yes
Observed passenger travel	Observed passenger-km	passenger-km	Yes
Counterfactual passenger travel	Baseline passenger-km	passenger-km	Yes
Incremental passenger travel	Difference attributable to project	passenger-km	Yes
Attribution method summary	Model/survey/control	Text	Yes
Mode share instrument ID	Survey/model version	Text	Yes
Baseline mode shares	Shares by mode	%	Yes
Baseline EI by mode		Text/value	Yes
Project EI		Text/value	Yes
Leakage assessment summary	Key risks and deductions	Text	Conditional
Leakage emissions	tCO₂e	Conditional
Baseline emissions	tCO₂e	Yes
Project emissions	tCO₂e	Yes
Net reductions	tCO₂e	Yes
Data gaps present	Yes/No	Text	Yes
Gap treatment description	Conservative treatment	Text	Conditional
Prepared by / date	Responsible person and date	Text / YYYY-MM-DD	Yes
Internal review by / date	Reviewer and date	Text / YYYY-MM-DD	Yes

Definitions and Acronyms

D.1 Definitions

For the purposes of this methodology, the following definitions apply.

Additionality means the demonstration that the project activity results in emission reductions that would not have occurred in the absence of the project and the incentive from carbon crediting.

Baseline emissions (BE_t) means the GHG emissions that would occur in monitoring period t in the absence of the project activity, representing delivery of the incremental passenger travel using baseline modes displaced by the project.

Baseline mode share (MS^BL_{m,t}) means the proportion of incremental passenger travel attributable to the project that would have been delivered by baseline mode m in the absence of the project, determined using evidence-based and conservative methods.

Baseline emissions intensity (EI^BL_m) means baseline emissions per passenger-kilometre for mode m, derived from energy use, fuel emission factors, occupancy assumptions, and operating conditions.

Counterfactual baseline ridership means the estimated passenger travel level that would occur absent the project intervention(s), used to determine incremental passenger travel.

Incremental passenger travel () means the passenger travel attributable to the project intervention(s) in monitoring period t that is above the counterfactual baseline passenger travel level, expressed in passenger-kilometres.

Induced demand means additional passenger travel that occurs as a result of the intervention and that would not have occurred absent the project, rather than travel displaced from baseline modes.

Leakage (LE_t) means an increase in GHG emissions occurring outside the project boundary that is attributable to the project activity and is measurable, attributable, and material under this methodology.

Project emissions (PE_t) means GHG emissions occurring within the project boundary in monitoring period t that are attributable to operation of the eligible public transport service to deliver the incremental passenger travel.

Project emissions intensity (EI^PJ) means emissions per passenger-kilometre for the eligible public transport service delivering the incremental passenger travel, expressed in tCO₂e/passenger-km.

Public transport means a passenger transport service available to the public or defined eligible passenger group, operated on a scheduled or semi-scheduled basis, with measurable passenger travel activity.

D.2 Acronyms

Table D-1. Acronyms

Acronym	Meaning
AFC	Automated Fare Collection
BE	Baseline Emissions
EF	Emission Factor
EI	Emissions Intensity
ER	Emission Reductions
GHG	Greenhouse Gas
LE	Leakage Emissions
PCS	Planetary Carbon Standard
PKM	Passenger-kilometre
QA/QC	Quality Assurance / Quality Control
VVB	Validation and Verification Body