An analysis of the Swedish HGV fleet with driving resistance in focus: vehicle parameters as a basis for HBEFA emission factor estimation

Ulf Hammarström
Mohammad Reza Yahya

In order to estimate energy use and exhaust emissions from road traffic, on a regional or a national level, one needs representative emission factors. Emission factors are estimated based on vehicle driving resistance. Driving resistance is estimated based on representative driving patterns and vehicle parameters. In the HBEFA program, used for estimation of road traffic exhaust emissions, the vehicle fleet is divided into vehicle categories. One such category is Heavy Goods Vehicles (HGV). The HGV category is divided into vehicle segments after maximum vehicle weight (GVW). One further division is into vehicle combinations, a rigid truck (RT) or a truck with trailer (TT). Vehicle segments are divided into Euro classes approximately corresponding to year model intervals. For each segment and Euro class there is a set of emission factors. Then there is need for vehicle parameters per vehicle segment and Euro class. HGV emission factors on the Euro class level are treated as independent of calculation year. Emission factors for HGV vehicles in HBEFA are calculated by means of the PHEM computer program. The PHEM simulations are based on driving resistance estimation. In order to estimate vehicle parameters, data available in the Swedish national vehicle register (1997, 2004 and 2009) and in transport surveys (1997 and 2003) has been compiled. Survey data including mileage is necessary in order to estimate vehicle parameters for average road conditions. The split into RT and TT segments demands access to mileage data describing the use of trailer. The total number of HGV in the Swedish vehicle fleet is approximately the same 2010 as 1990. Despite this there are most important changes within the HGV fleet in this time period, such as the proportion of trucks with GVW>26t has increased from 6 to 36 per cent. In this group there are some segments with very large changes of proportion. In parallel to an important change in the segment distribution one could expect a change in distribution also inside individual segments and Euro classes by time influencing the average vehicle parameters and finally the emission factors.



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