The standard 3.7m round top road hump was developed in the 1970s at the Transport Research Laboratory. Since the 1980s the regulations governing the use of humps in the UK has been relaxed to include flat top humps, raised junctions and speed cushions.
Nottingham County Council introduces speed humps on local roads where more than half the road is fronted by houses; more than 200 vehicles use the road during a peak hour; there are at least three road accidents in three years or two vulnerable road user accidents in three years; or if there is big public support for traffic calming.
When pedestrians are hit by a vehicle travelling at 40 mph, 90 out of a hundred are killed; 30 mph, 40 out of a hundred are killed; 20 mph, five out of a hundred are killed. Nearly all pedestrian casualties occur in built up areas.