Abstract
Driving during rainfall is less safe for motor traffic than for slow traffic. According to highway type the lack of safety is bigger if the maximum permitted speed is higher. There is almost no difference in season. On juntions the increase in the lack of safety is higher for slow traffic. Morning and peak hous have the highest increase in the insecurity of traffic. The extra insecurity which is derectly caused by rain can only be determined by taking into account the exposure of the different road users.