Collision warning–collision avoidance (CWCA) systems are showing increasing promise in preventing rear-end collisions. The effectiveness of many prototype systems has been evaluated on driving simulators or through numerical simulation, and several field tests are under way. Most investigations have focused on the safety benefits to host vehicles. Possible effects of CWCA-equipped vehicles on other traffic, especially the direct follower, have received little attention. Results of an evaluation study of this issue are presented. It is found that CWCA vehicles may have higher risk of rear-end collision with following vehicles. Thus, it may be necessary to design a CWCA system that is able to offer a balanced protection to host vehicles and to other traffic by considering possible effects of CWCA systems on other traffic.