Abstract
Applied psychological research can help to provide answers to questions from society. In this article an investigation is described, in which mailvan-drivers, working at the Netherlands Postal and Telecommunications Services (PTT), were encouraged to save energy by changing their driving behavior. After the programm has been carried out it was evaluated. Compared with a control-group, favourable effects of attitudes, social norms, reported behavior were found. Besides, energy savings of over seven percent were achieved, Social psychological models seem to be very useful in the investigation of implementing energysaving behavior.