In fatal accidents due to heavy duty trucks, the fatalities of occupants in passenger cars in which rear-end collision occur account for the largest percent. Collisions to the vehicles in traffic jams and collision to other accidents scenes on express ways can result in serious repercussions. Therefore the system which reduces the damage of collisions has long been demanded and here the world-first Pre-crash Safety (PCS) System for heavy duty trucks was developed. This system gives warning to the driver in case there is a possibility of collision with preceding vehicles, and activates the brakes to mitigate damage in case there is a higher possibility of collision. In order to get the maximum effect on the express ways where the trucks are in high speed, it is necessary to give warning and activate the brakes with relatively early timing. To achieve this function, a new algorithm was developed to correctly judge whether objects are on the host vehicle lane or not, and information from a millimeter wave radar, a steering angle sensor, and a yaw rate sensor were used. The timing and the strength applying brakes was also optimized.With PCS System for heavy duty trucks, the reduction of the fatalities in accidents on the express way is highly expected.