The effect of approaching vehicles on the lateral position of cars travelling on a two-lane rural road

The lateral position of cars was recorded in the presence of oncoming vehicles on a two-lane rural road. A car-following technique was used to obtain video recordings with a camera mounted unobtrusively on the experimental vehicle. The study investigated lateral positioning over longer segments of such episodes than previously. As Vehicles approached from opposite directions, there was a general systematic movement away from the road centre-line in the period immediately prior to meeting. For those vehicles initially travelling closest to the road-edge, this diverging away from the centre-line was preceded by a tendency to move towards it with the smallest lateral displacement occurring at between 5 and 6 seconds before reaching the oncoming vehicle. Three alternative classes of explanation can be invoked to explain such a pattern of driver steering performance. The driver's perception of the straight ahead path may be influenced by the oncoming vehicle as a real-world instance of the Dietzel-Roelofs effect. Drivers may monitor the path of their Vehicles and precisely adjust the periodic lateral movement based on detailed preview information as the oncoming vehicle approaches. Finally, a signalling or preparatory positioning cognitive strategy may be used by drivers when controlling their lateral position in these circumstances.