The topic of this paper concerns specifically cyclist and motorcyclist accidents and assessment of measures to reduce them. Countermeasures aimed at reducing the quantity of exposure as well as those which improve the quality of exposure by reducing the risk of involvement per unit measure of exposure quantity will be discussed as will reduction of severity of the outcome of the collisions which do occur. These pre-crash, and crash phase countermeasures will be related to the human, vehicle and environmental aspects of the road-use system.