Most pedestrian crashes occur while the pedestrian was attempting to cross the road. One way of preventing crashes between vehicles and pedestrians is placing them at different levels, or ‘grade separating’ them.

In urban situations where pedestrian crossing signals would cause congestion or crashes (due to high traffic speeds), a grade separated pedestrian crossing, such as an overpass (or bridge, footover bridge) or an underpass, may be used. Outside of urban areas in situations where there is pedestrian demand in high-speed environments, this treatment may also be applied.

Grade separated pedestrian crossings reduce pedestrian crashes but they also have some disadvantages:

• they are costly
• they sometimes become crowded with street traders
• pedestrians may avoid them if there are a lot of steps to climb up or down
• if they are not well-lit and patrolled, they may pose a personal security risk
• underpasses are susceptible to flooding and can become unusable if not routinely maintained.