How can I drive energy-efficiently? – Developing a set of ecodriving-tips for hybrid electric vehicle (HEV) drivers that promotes action regulation

To advance ecodriving skills in hybrid electric vehicle (HEV) drivers, and thus, facilitate fuel-efficient driving behavior, a set of 15 ecodriving-tips was developed and tested. In part 1, telephone interviews with HEV drivers  and car  manufacturers’  owner manuals  were  analyzed to  extract  ecodriving-related  statements. Whereas the owner manual statements could not be used further due to their low level of detail, the interview statements served as a basis to develop a final set of 15 ecodriving-tips. To ensure technical correctness, a technical drivetrain expert was consulted. The final set was formulated in three versions with increasing level of detail. Whereas Version 1 was based on materials currently used in practice (e.g., owner manuals), Version 2 and 3 were psychologically-grounded and developed in relation to the concepts of implementation intentions and mental models. In part 2, an online study with two points of measurement and a randomized controlled design was conducted to test the three formulations. For this, HEV drivers were recruited and randomly assigned to one of three groups. Both, at baseline and follow-up, participants evaluated the ecodriving-tips largely positive. The positive evaluation was associated with high ecodriving-related perceived self-efficacy and high ecodriving knowledge. At follow-up, no significant differences were found between the three groups regarding central indicators of ecodriving behavior. However, participants that received the most elaborated version of the ecodriving-tips, significantly reduced their fuel consumption by 4 %. Taken together, participants evaluated the ecodriving-tips largely positive. Yet, neither the evaluation of the ecodriving-tips nor their effectiveness in promoting ecodriving behavior differed between the three formulations.