Truck accidents are a major factor in the accident statistics. This paper deals with typical risk situations in truck-to-car collisions with respect to accident prevention. From a representative material of nearly 1400 truck-to-car accidents the pre-crash situations are described. It is shown that the signal effect of trucks especially in night-time and in bad weather conditions is insufficient. This results in an increased rate of car crashes into the side and rear end of trucks related with conspicuity problems. Proposals from current research work are made to improve the signal effect of trucks including an efficiency assessment. A passive conture marking seems to be an essential contribution to accident prevention and would enable retro-fitting of existing trucks, which is necessary for short term improvement.