4.3 Secondary effects of weight reduction
With the reduction of weight, other effects can be achieved and thus more energy be saved. First of all, less material has to be produced and recycled or disposed. However, the production of light-weight materials, which are in many cases used to achieve a weight reduction, normally consumes more energy than the production of heavier components. Therefore this secondary effect is normally having a contrary im- pact, with more energy being consumed for the production of the lighter vehicle. This ef- fect is part of a full life cycle assessment and will not be considered here.
In the use phase, some secondary modifications can be realised if the vehicle is sup- posed to achieve the performance of the original vehicle. This applies to the tuning of the engine and adjustments in the transmission to the new power-to-weight ratio. Only with these modifications, the full potential of the weight reduction can be taken ad- vantage of.
Other secondary effects are more complicated and change the functional unit. Possibili- ties are the downsizing of the engine, so that it will have the same power-to-weight ratio, which will result in even less final energy consumption and a further weight reduc- tion. Other components, like the frame, can be adjusted as well. These possible sec- ondary saving effects, which require a new vehicle design, have been assessed to be in the range between 16 % and 50 % of the primary saving effects of weight reduction ([EBERLE 1999]).
Cargo vehicles will normally take a payload up to the maximum allowance if possible (e. g. 40 t for articulated trucks). Especially for freight trains the maximum cargo is rather weight-limited than volume-limited [STODOLSKY et al. 1998]. In this case the weight reduction permits the transportation of a higher payload and thus e. g. less vehicles are needed to transport a certain amount of goods from one place to an- other. These indirect energy savings for weight limited transport are the result of a lower mileage for the same transport performance and can be calculated in comparison to the driving distance without weight reduction, the original functional unit. This effect has been calculated for trucks and freight trains in the respective sections.