A large-scale study on the speed-calming effect of speed humps

Inappropriate speeding is one of the main causes for traffic-related injuries and fatalities. Studies have shown that more than 50 % of Danish car drivers regularly speed on urban roads and nearly 75 % of them speed on rural roads. Physical speed-calming measures, particularly speed humps, are widely used to reduce speeding in urban areas in the Danish road network. However, speed humps are often located based on reasons other than ensuring that they have the best effect on reducing the speed of vehicles. Furthermore, their speed-calming effect is not utilised sufficiently. This study evaluated more than 570 speed humps on roads with a 50 km/h speed limit. The main results reveal that speed increases with an interval between speed humps of up to 200 m at approximately 60 km/h. Additionally, a positive correlation was found between the distance from the roadside to the roadside buildings. The actual interval between speed humps ensures that suitable driving behaviour is carried out is 52 m, 70 m and 164 m for through roads, main roads and residential roads, respectively, in cases in which roadside buildings are situated farther from the road. Similar values were found for the intervals between speed bumps on these three types of roads (67 m, 89 m and 261 m, respectively) when there is a shorter distance between the roadside and the roadside buildings. Overall, speed humps are an efficient way to reduce speeding in built-up areas; however, aside from the interval between the speed humps, the distance from the roadside to the roadside building is the only significant factor contributing to the speed of the car for drivers on these roads.