How do you calculate transportation carbon emissions?

2 Data sources

To apply the basic formula, you need data on the vehicle type, the distance traveled, and the fuel efficiency. You can obtain this data from different sources, depending on the scale and scope of your analysis. For example, if you want to estimate the carbon emissions of a specific road or corridor, you can use traffic counts, vehicle classification, and average speed data from traffic sensors or surveys. If you want to estimate the carbon emissions of a city or region, you can use travel demand models, which simulate the travel behavior and patterns of the population based on land use, transportation network, and socio-economic factors. If you want to estimate the carbon emissions of a country or a global sector, you can use aggregate statistics on vehicle stock, fuel consumption, and vehicle kilometers traveled from national or international databases.

3 Tools and models

Calculating and incorporating various variables and factors into the transportation carbon emission estimation process can be simplified by using certain tools and models. For example, the EPA's MOVES model estimates emissions from on-road vehicles at various scales and resolutions, based on vehicle activity, emission rates, and meteorology. The California Air Resources Board's EMFAC model is designed to estimate emissions from on-road vehicles in California, while the European Environment Agency's COPERT model estimates emissions from road transport in Europe. The Argonne National Laboratory's GREET model evaluates emissions from various transportation modes and fuel cycles, with well-to-wheels and life cycle analysis, while the HBEFA model developed by a consortium of European countries assesses emissions from road transport in Europe, using data on vehicle fleet, activity, speed, and emission factors.

4 Uncertainties and limitations

When calculating transportation carbon emissions for transportation planning and policy making, it's important to be aware of the uncertainties and limitations that may arise. These can include data quality and availability, emission factors, and other factors such as traffic congestion, driving behavior, cold start, idling, road grade, weather, or emission control systems. Data accuracy and reliability will depend on the source, method, frequency, and coverage of the data collection and reporting. Emission factors can vary depending on fuel type, quality, blend, vehicle technology, age, and maintenance. Furthermore, some emission factors may not accurately reflect actual conditions or vehicle performance. Therefore, it is essential to consider all these sources of uncertainty and limitation when calculating transportation carbon emissions.

5 Best practices and tips

To improve the quality and usefulness of your transportation carbon emission calculation, you should define the purpose and scope of your analysis, choose the appropriate method and tool, and report and communicate the results. Consider the advantages and disadvantages of different methods and tools, as well as the data requirements and availability. When presenting the results, explain the main findings and implications, and address any uncertainties or limitations. By following these steps, you can calculate transportation carbon emissions for your projects or policies, which will help inform your decisions and actions.