of road vehicles good data are available for passenger cars only. The weight induced energy savings with adjustments in the axle transmission, however, have been studied by few sources only, while the debate on the functional unit of passenger cars is still go- ing on. For other vehicles, no adjustments have been taken into account by the ana- lysed literature, the performance of passenger vehicles will therefore change with a weight reduction. For freight transport a higher payload will in many cases maintain the functional unit. Specific energy savings for other road vehicles are rather estimates than precise scientific chargeable tests or simulations. Good data for the relative energy sav- ings of rail vehicles are available mainly for short distance trains with frequent stops and accelerations. For other vehicles estimates with uncertainties have been undertaken as well. Relative energy savings have a maximum range between 0% and 10% and the values used in this study are plausible in comparison with values verified in tests and simulations. Uncertainties, however, arise from the ascertainment of the total weight and energy consumption of the train relations, because trains vary much, mainly de- pending on the number of rail cars they are composed of.
Data uncertainties in the life-time performance of road vehicles arise from the share and the use of exported used vehicles. Differences between countries are also consid- erable, depending on the infrastructure, climate, lifestyle, age of the vehicles and legisla- tion. For rail vehicles, a “real” value for the life-time performance is critical because lo- comotives and rail cars may have a very different life-time. Some rail vehicles have a very high life-time performance due to a revision after 20 or 30 years. For a weight re- duced vehicle it has to be considered if the weight reduction is maintained after the revi- sion (e. g. previous weight reduction by a lighter chassis).