2.2 Specific energy savings
Besides direct energy savings (Chart 1), a weight reduction permits a higher payload. In case of weight limited transport for an articulated truck and freight train respectively three and four times the direct energy savings can be achieved. Therefore the life-time energy savings in section 2.4 consider the share of weight limited transport.
Source: IFEU 2002 from various sources
Specific energy savings for a 100 kg weight reduction of one vehicle mainly depend on its use and the general physical specifics. Highest energy savings can be found for ve- hicles which are used with frequent stops and accelerations. Therefore cars and city buses have the highest specific energy savings among the road vehicles and regional trains and subways/ urban trains among the rail vehicles (Chart 1). For other vehicles with a more steady and higher speed, like long distance buses, trucks and trains, the weight independent aerodynamic resistance consumes a greater share of energy.
Passenger cars have particularly high specific energy savings, because additional en- ergy savings can be achieved by maintaining the performance of the original vehicle (e. g. by adjustments of engine size or axle transmissions). Such effects have not been considered for other vehicles by the analysed literature.
Chart 1: Specific primary energy savings for the use of selected vehicle examples
freight train freight train
Specific primary energy savings [MJ/(100 km*100 kg)]