"Times change!" - Analysis of warning points of a prototypical warning concept based on Car2Car communication

Due to an increased development of car-to-car communication systems in vehicles in the last years, it is possible to inform drivers prospective at an early stage of a potential hazard situation (e.g., position and distance), even when the hazard is not recognizable for drivers. In the Car2X-Safety project of Niedersachsisches Forschungszentrum Fahrzeugtechnik (NFF), a prototype of a two-stage warning system based on car-to-car communication was developed which informs drivers well in advance that a potential critical situation is approaching (1st stage) and also warns them in a 2nd stage before the situation occurs. Beside the evaluation of the effectiveness of these kinds of systems [1], further key questions are when drivers like to be informed and warned by these systems and how these timings (1st and 2nd stage) are influenced by the driving situation (e.g., rural road, highway). To that aim, a driving simulator study was conducted to investigate drivers' required timing of this two-stage warning system in three different driving scenarios (urban road, rural road, highway). For examining the required timing of the two stages the method of adjustment [3 and 4] was used. A total of 24 subjects (11 female, 13 male) with an average age of 29.1 years (SD = 11.6 years) participated in the study. The results showed that drivers do not differentiate between the driving scenarios in their required timing for a potential critical incident. This effect was found both for the 1st and 2nd stage. Drivers reported to be informed approximately 26.5 s (1st stage) and warned approximately 12.1 s (2nd stage) before the critical incident occurred. The results of the study contribute to an approach to collision warning timing of assistance systems based on car-to-car communication.