Background, Goal and Scope. The transport sector contributes significantly to the global energy consumption and greenhouse gas emissions. Among other measures, also light-weighting of vehicles is discussed as a way to reduce the energy consumption and, thus, also CO2 emissions of transport. Currently, most Life Cycle Assessments (LCAs) use rough estimates on potential energy savings by light-weighting, which are not comparable due to different scopes and methodologies. This paper therefore presents a set of scientific data for use phase energy savings for different vehicle types for a harmonised and, thus, comparable weight reduction of 100 kg. Road and rail vehicles, ships and aircrafts are covered in this paper. Besides an analysis on a per vehicle basis, the potential contribution of light-weighting to a reduction of the global transport energy consumption is also estimated. All analysed energy savings are independent of the technical realisation of the weight reduction (e.g. new materials or improved design or logistics). The data can therefore be used in LCAs of different light-weighting technologies. Methods. Available data have been analysed in respect to system boundaries and methodologies. Several sources which are suitable for a comparable quantification of specific energy savings per vehicle-km or the use phase energy savings, for example, have been identified. In order to obtain more differentiated data and close the data gaps, specific modelling has also been undertaken for articulated trucks. Data have been checked for plausibility against the analysis of physical resistance factors and been converted to a harmonised and, thus, comparable weight reduction of 100 kg. Results and Discussion. The energy consumption per vehicle-km depends largely on the physical resistances which the vehicle has to overcome during its operation. Ground vehicles operated in urban areas, with frequent stops and accelerations, are generally capable of higher energy savings for a given weight reduction compared to vehicles on highways at steady speeds. The total use phase energy savings for a 100 kg weight reduction also depend on the total use phase transport performance. Road vehicles realise about the lowest use phase energy savings due to the limited use phase mileage. Rail cars commonly have a higher use phase mileage and can therefore achieve higher use phase energy savings. Even higher savings are estimated to be achieved by a weight reduction of high-speed ferries (about 10 times higher compared to rail vehicles) and aircraft (about 100 times higher compared to rail vehicles). On a global level, however, road vehicles and especially passenger cars could make the highest contribution to reduce energy consumption by light-weighting. This is due to the high share of these vehicles on the global energy consumption (because of the huge number of these vehicles) and also a considerable potential to realise a further weight reduction. Conclusion and Perspectives. Light-weighting is one way of reducing transport energy consumption in the use phase. The differences in use phase energy savings for a 100 kg weight reduction between the vehicle groups are considerable and allow for the identification of priorities for future light-weighting efforts. The contribution to a reduction of the global transport energy consumption, in turn, depends on the further potential for a weight reduction and on the number of vehicles which can be weight reduced. The OECD market of private passenger cars and trucks, for instance, offers a good perspective due to a high contribution to the global transport energy consumption, a considerable potential for weight reduction and a high turnover rate of the vehicle fleet. The benefits will be realised after a substantial replacement of the existing fleet with new, weight-reduced vehicles.
