The following study describes drivers' speed behaviour in encounters with pedestrians at a non-signalized zebra crossing. The aim being to identify so-called "ideal" situations that will form the basis for recommendations for designing an RTI-based system for dynamic speed adaptation at zebra crossings. The speed profile of approaching passenger cars was registered along with the other variables, such as pedestrian presence and their time of arrival at the curb in relation to the approaching car's expected time of arrival. The results show that the pedestrian passes first in only 5% of all encounters. In 73% of critical encounters the driver maintains the same speed or accelerates and in only 27% slows down or brakes. These figures indicate that maintained high speed (even exceeding the speed limit of 50 km/h) is the signal from the drivers that they do not intend to give way to the pedestrian at the zebra crossing. The "signalling" takes place about 40 to 50 m prior to the zebra crossing, after which the driver eases the accelerator and the speed decreases to some degree while passing the zebra crossing. This strategy proves fairly effective and in most cases the car passes first. These results indicate that drivers delegate the responsibility of avoiding a collision to the pedestrians. In order to attain an "ideal" speed behaviour in encounters involving a pedestrian at the zebra crossing, a warning signal should be given to the driver when the car reaches the "braking distance + 3 second" line. This is about 65 m before the zebra crossing at a speed of 50 km/h and about 33 m at a speed of 30 km/h. If the driver does not commence braking within 2 seconds, the dynamic speed-limiter should be executed and brake the car with normal braking (4.5 m/s2) to 30 km/h, following the "braking distance + 1 second" curve. This is about 36 m before the zebra crossing at a speed of 50 km/h and about 18 m at a speed of 30 km/h. The 30 km/h speed limit should then be maintained until passing the zebra crossing. (A)
Abstract