Many transit bus crashes in which the bus is at fault are sideswipes caused by the drivers' inability to see objects or other vehicles in the blind zones of the mirrors on the bus. This research compared relatively new camera-based systems to sensor-based and mirror-based systems for transit buses for their potential for side collision avoidance and their reliability in rain and at night. The camera-based system for transit buses under evaluation was a system that incorporates video cameras installed on the outside walls of the bus, aimed at the left and right rear sides of the bus, and two monitors connected inside the bus to provide the driver with an image.