Speed humps create a gentle rocking feel in a car when it passes over it with the determined speed limit. If a car is driving at a high speed, the hump will jar the car and its contents which will cause discomfort to the passengers inside and disruption to the cargo. In this way, vehicles are forced to pass over them with both the wheels reducing the possibility of bottoming out.
They come in a wide variety of profiles and travel lengths. The length range varies from 3 to 20 feet. Any travel length longer than this will only cause up and down motion, and a shorter travel length leads to two rocking movements as each set of wheels passing over.
Speed humps are placed in a series which maintains the speed reduction via a long corridor. These vertical deflections are not idea for arterial roads, emergency routes or any street where it is easy to evade the hump by driving on a shoulder. Due to this, they are installed in a single or double lane in the local urban settings where there are closed sewers and curbs. If they are installed nearby a shoulder, then they are twinned with bollards to avoid the cars from leaving the roadway.
These are more of an aggressive traffic calming option than the speed humps, and they are useful in places where the pedestrians and cars have to share the space closely such as parking lots or driveways. A speed bump tends to slow down the traffic to 2 to 10 mph giving people time to safely react to each other.
They are rarely used on public roads as they need vehicles to come to near stop to pass over them and cause damage to the cars moving at a regular speed. They are usually 2 to 4 inches high. However, they have a shorter travel distance than the speed humps. These obstacles are under a tire of a vehicle for less than half of a full wheel rotation and with standard widths between 6 inches to 2 feet. The height to travel distance ratio is always smaller than the vehicles passing over it. The car moving at high speeds will receive two huge jolts. Speed bumps are placed at intervals to maintain speed reductions. They are spaced judiciously as they are more incompatible to go over any speed and are used in small areas. They can also deliver shocks. Hence they are known by the names like speed breakers in India, judder bars in New Zealand, sleeping policeman in the UK, road turtles in the Southern US, and dos-d’âne in French, meaning humpback.