Vehicle emissions prediction model

The Vehicle Emissions Prediction Model (VEPM) has been developed by Waka Kotahi and Auckland Council to predict emissions from vehicles in the New Zealand fleet under typical road, traffic and operating conditions. The model provides estimates that are suitable for air quality assessments and regional emissions inventories.

Since its release in 2008, VEPM has been successfully used in Auckland and around New Zealand to estimate vehicle emissions in air quality assessments for road projects. An important feature of the model is the ability to estimate changes to vehicle emissions in future years (out to 2050).

Note:

To understand the limitations and uncertainties of average-speed models like VEPM in relation to modelling changes in speed in urban areas (low speeds) on greenhouse gas emissions, refer to the following research reports.

Effect of speed on greenhouse gas emissions from road transport - a review, Emission Impossible Limited and EMM Consulting, December 2022. Revised September 2023 [PDF, 1.1 MB]

The effect of speed on emissions: summary report, Emission Impossible Limited, May 2023. Revised 20 September 2023 [PDF, 1.1 MB]

For guidance on the application of VEPM emissions rates to traffic data or transport model outputs for the purpose of estimating the change in vehicle greenhouse gas emissions from specific transport interventions, refer to the following research report:

Transport modelling methodology for determining greenhouse gas emissions from vehicles, Beca Limited, May 2024 [PDF, 962 KB]

For calculating emissions from transport model outputs use the Traffic Model Emissions Tool, which applies emission rates from VEPM to the output data from the traffic model.

Traffic Model Emissions Tool

Using the VEPM

VEPM is a publicly available database. A summary of the current and previous versions of VEPM are provided below.

If you wish to receive updates on VEPM, please email environment@nzta.govt.nz with Vehicle Emissions Prediction Model in the subject line and you will be added to the mailing list.

Current and past versions of the VEPM

Version	Notes
VEPM 7.0	The current version of the model is available at https://vepm.co.nz(external link) The previous version of VEPM (VEPM 6.3) was released in March 2022. An upgraded VEPM 7.0 has been developed from an Excel spreadsheet (VEPM 6.3) to a website interface. The benefits of this are: improved run times, particularly when running multiple scenarios reduced likelihood of unintended errors arising by knowingly or unknowingly changing Excel cells increased confidence in the model outputs due to improved visibility of the calculation logic for the model developers simpler annual updates provisions of a database of model outputs, available as an input to other emissions calculation tools such as the Project Emissions Estimation Tool (PEET). There have been no technical changes between VEPM 6.3 and VEPM 7.0.
VEPM 6.3	Changes to the previous version VEPM 6.2 released in 2021 include: updating the fleet profile based on updated vehicle kilometres travelled (VKT) data from the Vehicle Fleet Emission Model (VFEM3) provided by Ministry of Transport revising assumed emission standards for Japanese used imports from 2010 onwards revising the assumed date of introduction of Euro 6/VI standards in VEPM to reflect a likely 'no new policy' scenario updating the application of fuel correction factors.
VEPM 6.2	Changes to the previous version VEPM 6.1 released in 2020 include: updating the fleet profile based on updated VKT data from VFEM3 provided by Ministry of Transport revising the assumed date of introduction of Euro 6/VI standards in VEPM improving the assumptions in VEPM to split heavy commercial vehicle VKT between rigid and articulated truck categories providing methane (CH₄) and nitrous oxide (N₂O) emission factors and calculation of carbon dioxide equivalent (CO_2-e) emission factors incorporating updated emission factors from the latest version of COPERT (the EU standard vehicle emissions calculator) updating degradation factors for light duty vehicle carbon monoxide (CO) and nitrogen oxides (NO_X) emissions updating light duty gradient correction factors.
VEPM 6.1	Changes to the previous version VEPM 6.0 released in 2019 include: changes to significantly reduce bulk run processing times and rationalise the spreadsheet model replacing all existing Euro emission factors with emission factors from the latest version of COPERT incorporating articulated truck emission factors and estimated VKT into VEPM incorporating bus emission factors into VEPM incorporating New Zealand real world fuel consumption correction factors for diesel passenger cars and diesel light commercial vehicles.
VEPM 6.0	Changes to the previous version VEPM 5.3 released in 2017 include: updating the fleet and extending VEPM to 2050 creating separate categories in VEPM for light duty hybrid, plug-in hybrid and electric vehicles adding a new category for electric heavy-duty trucks and buses updating all Euro emission factors with emission factors from the latest version of COPERT incorporating new Euro 6 emission factors for passenger and light commercial vehicles updating the method for calculation of tailpipe CO₂ updating brake and tyre wear emission factors.
VEPM 5.3	Changes from the previous VEPM 5.1 released in 2012 include: incorporating nitrogen dioxide (NO₂) speeds for light vehicles up to 110km/h updates to the emission standard introduction date and country of origin assumptions updated emissions factors for Euro 5, Euro 6 and Euro V based on COPERT, and addition of Euro VI category.
VEPM 5.2	Beta version of model, which was not formally released but has been made available on specific request. This version included updates based on vehicle kilometres travelled (VKT) data from the Vehicle Fleet Emission Model (VFEM) provided by Ministry of Transport.
VEPM 5.1	Previous version of the model released in 2012.

Privacy statement

When you email us to request being updated on VEPM, we collect your name and email address. These details will be added to a mailing list that is only used to let you know about VEPM updates, for example when we make a change to the tool, or when we conduct surveys regarding improving the tool. You can request access to and correction of that information at any time by emailing environment@nzta.govt.nz

If you no longer wish to receive emails about the VEPM, please tell us; and remember to check this webpage regularly for updates and changes to the VEPM tool.

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Disclaimer

Waka Kotahi does not represent or endorse the information, content, presentation or accuracy of this vehicle emissions prediction model and its contents.

Read the full disclaimer(external link)

User guides and technical information

Waka Kotahi has prepared a VEPM user guide that describes the modelling process and the background for the VEPM method. The VEPM user guide and a summary of the development of VEPM are provided below. Additional supporting technical information can be found in the research reports which are referenced from the user guide.

Online services

Using the VEPM

Current and past versions of the VEPM

Privacy statement

Disclaimer

User guides and technical information