The Handbook of Emission Factors for Road Transport

Two small errors have been noted in the German fleet scenario for HBEFA 5.1:

• Bifuel CNG/Petrol LCV: mileages were missing for CNG driving shares for most years in the time series

• 4-stroke mopeds: mileages were missing for most years in the time series

Consequently, no emission factors have been output in “weighted” queries for the respective vehicle types and years.

These errors will be corrected with Version number 5.1.004.
We will carry out the update immediately.
For users, the update will take effect with the next application restart.

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.