This paper reviews results from a series of studies in which latencies in driver/ vehicle steering responses were measured on the road, unobtrusively, and with representative samples of unsuspecting drivers. Based on the fact that an obstacle on the road shoulder induces an avoidance response, i.e., a lateral displacement towards the middle of the road, a stimulus event was introduced at various distances when a car was approaching so that the time available to drivers for an avoidance response was known. It was found, first, that the average steering response started at latencies greater than 1 s, reached the half-way point at 2.5 s and the maximum at 3-4 s, depending on the situation. Second, this method was applied in a project on the effects of a warning flasher on driver behavior in school zones. It was found that the flasher reduced the drivers’ steering response latencies. This was supposedly the first time to measure drivers’ attention unobtrusively.
