Effects of version 3.3 of the Handbook on Emission Factors for Road Traffic (HBEFA) on air pollution prevention planning
On the basis of the emission values given in the handbook HBEFA, the air pollution and greenhouse gas load caused by road traffic can be calculated.
For the vehicle categories passenger car, light and heavy duty vehicles, services buses and touring coaches as well as motorbikes emission factors are stated in HBEFA differentiated according to different emission concepts (Euro 0 to Euro 6/V) and traffic situations.
HBEFA provides emission factors for all regulated pollutants as well as for several not regulated pollutants including CO2 and fuel consumption.
The fields of application range from the emission calculation within the scope of an EIA procedure or the determination of emissions for small-scale planning up to complex air pollution prevention planning.
The necessity of an adjustment of the emission factors for passenger cars given in HBEFA 3.2 results from NOx emission measurements at new diesel passenger cars in Europe and the USA. As the values measured during real operation and for temperatures below 20 °C were higher compared with those obtained in the test stand, ERMES/HBEFA has decided to take action. Already before the regularly planned new version HBEFA 4.1 (with publishing expected in the first half of 2018), version 3.3 is an intermediate update. Here, the NOx factors for the diesel passenger cars classes Euro 4, 5 and 6 have been updated.
New emission factors, why?
- It is now more clearly taken into account that the nitrogen oxide emissions (NOx emissions) of a motor and the function of the exhaust gas treatment system strongly depend on the ambient temperature. In the past, it was assumed that an engine at operating temperature has a stable emission behaviour also for cold temperatures. Thus, on the roller test stand the measurements were taken for a temperature range of between 20 °C and 25 °C.
- In HBEFA version 3.3 – in addition to the measurements on roller test stands – now also exhaust gas measuring values are taken into account which have been determined by means of a PEMS (Portable Emission Measurement System) during real drives on the road.
- Furthermore, the statistic data basis of the measured Euro 6 diesel passenger cars has improved.
What are the effects of the new findings on NOx emission factors?
The emission factors of all diesel passenger cars of class Euro 4, 5 and 6 have increased in the data base. Thus, according to the respective traffic situation an increase of the calculated NOx emissions of passenger cars on roads of 30 % to 50 % can be expected.
Therefore, an increase of the emission factors has a direct effect on the evaluation of air pollution prevention measures planned by the municipalities.
