The Handbook of Emission Factors for Road Transport

So far, the mileage correction for hot NO2 emission factors of heavy duty vehicles (HDV) is not carried out in HBEFA 5.1 if NOx (on which NO2 depends) is not selected in an emission factor query. This needs to be corrected. The update will carry version number 5.1.003.

We will carry out the update this coming Thursday, 15.01.2026, from 17:00 CET; it may take about one hour.

Users do not need to take any action. The new version will automatically be selected in the front-end application and in API queries unless another version is explicitly set. Only queries for hot emission factors of HDV (i.e. trucks, coaches, buses) that included NO2, but not NOx, are affected.

We are using the opportunity to also implement a small improvement for API users: The "hbversion_int" used in an emission factor query will be returned in the "Input_ pars" dictionary for better traceability.

We will implement an update tonight on the HBEFA server to correct some errors identified in HBEFA 5.1 since its publication.

For details on the changes, please see: HBEFA5.1.002_Update_Dec2025.pdf

Since the changes are implemented on the server, HBEFA users do not have to download a fresh desktop client (front-end application) due to the update.

‍The update will be implemented tonight, i.e. on December 17, 2025, from 18:00 CET (likely for not more than 1 hour) on the central server. Several server restarts may be possible during that time.

A new version of the desktop client will be made available in the next days - with the only change being that the button to open the Help file has been moved to a separate "Help" menu in order to be found more easily. It is completely optional to download this new version. The content corrections on the server will also be effective with the desktop client used so far.

The free "online version" on this website will be updated in the next days to reflect the changes in the 5.1.002 update.

We are pleased to announce the release of HBEFA Version 5.1!

Registered and new users can obtain the new version by filling in the registration form on this website under SOFTWARE > GET THE HANDBOOK.

Version 5.1 is a major update. All contents of the Handbook have been updated. Version 5.1 represents a substantial extension of contents compared to previous versions, with additional pollutants, subsegments, and about five times as many base emission factors as in HBEFA 4.2. Furthermore, the new version is implemented as a user-friendlier Python-based client-server solution (as opposed to the previous MS Access-based versions).

An overview and documentation of the updated aspects is available under METHODOLOGY > REPORTS > “HBEFA 5.1 Update Documentation”

Please see the updated help file on this website under SOFTWARE > VERSIONS >HBEFA 5.1 for a quick start with the new application.

Unfortunately, the French country data inputs are slightly delayed. They will be updated in a few days. Since the new application is a client-server solution, it will not need to be downloaded or installed afresh after the update. For the moment, it is just not possible to calculate results weighted with a fleet composition for France.