A bike box is a designated area at the front of a traffic lane at a signalized intersection that places the bicyclist ahead of queuing motor vehicle traffic during the red signal phase. The bike box increases visibility of bicyclists at intersections (the most common location for bicycle collisions).
It is also intended to prevent conflict between bicyclists and motorists continuing in different directions. For example, a bicyclist traveling straight through an intersection should be centered in the traffic lane giving a right turning motorist room to turn safely next to them. Likewise, a bicyclist turning left from a lane that can either turn left or go straight should be position in the center of the traffic lane in front of motor vehicles intending to travel straight so that their paths do not cross.