sides) present a practical limitation on speed due to the mechanical impact of the shoe, and 161 km/h 0 abbr=on is considered the upper limit of practical third-rail operation. The world speed record for a third-rail train is 109 mph attained on 11 April 1988 by a British Class 442 EMU.

In the event of a collision with a foreign object, the beveled end ramps of bottom-running systems can facilitate the hazard of having the third rail penetrate