Handbook emission factors 5.1
Project duration: 2021 to 2025
Funding: Germany, Switzerland, Austria, France, Sweden, Norway
Project team: Hausberger, Weller, Opetnik, Dippold, Landl, Present, Nöhrer, Vuckovic
In October 2025 the latest version of the Handbook Emission Factors (HBEFA 5.1) was released as a major update. A particular focus has been set on new aspects that gain importance as road vehicle fleets evolve due to emission and CO2-regulations– such as non-exhaust emissions (NEE), cold start extra energy consumption and emissions, non-regulated pollutant emission, and tampering and deterioration of vehicles.
We performed emission tests on our LDV and HDV chassis dynamometer and in real traffic with on-board measurement systems and we collected new test data from all HBEFA partner labs. Overall, 87 heavy duty vehicles (HDVs) and 90 cars and light commercial vehicles (LCVs) between EURO 6a and 6e have been tested for the update. The data is uploaded in our database, which provides the input data for our emission model PHEM to produce emission maps and vehicle specifications as basis for the simulation of all exhaust and non-exhaust emission factors of HBEFA. PHEM simulates forces and power from the equations of vehicle longitudinal and lateral dynamics from the vehicle input data for more than 1800 different traffic situations (i.e. driving cycles) and calculates based on these data the emission values from the emission maps.
We developed a now model approach for the simulation of cold start related extra emissions, which allows to use all cold started emission tests for model parametrization. This allows for the first time the consideration of cold start emissions from HDVs in HBEFA and to use a broad set of test data for cars. Results show, that cold starts have significant impact on the emissions of modern vehicles in urban areas where most starts appear.
Figure 1: NOx emissions of Euro 6d passenger cars in different scenarios
For the non-exhaust emissions novel simulation methods have been developed, using brake power and rotational disc-speed for brake wear particles and slip power for tire and road wear particle emission simulation. So far, the data for model parameterization is quite limited (8 tested brake systems and 6 tested tires), but the model is capable of simple updates when more data becomes available. Results show, that brake wear emissions dominate vehicle PM10 and PM2.5 emissions in urban traffic. In rural and motorway driving resuspended PM, road and tire wear are more important. Due to increasing shares of electric motors in vehicle drive trains and due to emission limits for brake wear in EURO 7, brake emissions and thus NEE in urban areas will drop in future significantly.
Figure 2: Non exhaust emission factors for all traffic situations in HBEFA for flat roads for the passenger car fleets 2025 and 2030 with average curve radii