Speed bump

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For other uses, see Speed bump (disambiguation).

Speed bump made of asphalt

A speed bump (British English a speed or road hump, sometimes colloquially a sleeping policeman) is a traffic calming tool designed to slow traffic or reduce through traffic. A speed bump is a bump in a roadway that may be circular, parabolic, or sinusoidal, and it may have gaps near the curb to allow drainage. The speed at which a vehicle can safety pass a bump decreases with the bump's slope. Speed bump heights range from as little as 2 inches to as much as 6 inches, and they can vary in length from less than 1 foot (30cm) to as much as 10 feet (3m). Speed bumps longer than 10 feet are usually called speed humps, and they are often used to slow traffic in residential neighborhoods.

The use of speed bumps is widespread around the world, and they are most commonly found where prevailing vehicle speeds are expected to be low.

Speed bump made of rubber

Although speed bumps are very effective in keeping vehicle speed down, their use is sometimes controversial as they can cause noise and possibly vehicle damage if taken at too great a speed. Poorly designed speed bumps often found in private car parks (too tall, too sharp an angle for the expected speed) can be hard to negotiate in vehicles with low ground clearance, such as sports cars, even at very slow speeds.

1 History
2 Road humps in the UK
3 Criticisms
4 Dynamic speed bumps
5 References
6 Bibliography

[edit] History

The speed bump was invented in the 20th century. Prior to the invention of the automobile and the widespread use of smooth asphalt or concrete pavement, street vehicles could not travel at the sort of speeds at which speed bumps are intended to reduce.

On March 7, 1906, the New York Times reported that Chatham, New Jersey planned to install what were probably the first automobile speed bumps/humps ever. According to the article, Chatham planned to raise its crosswalks five inches above the road level, adding, "This scheme of stopping automobile speeding has been discussed by different municipalities, but Chatham is the first place to put it in practice" ^[1].

Another speed bump genesis story takes place during World War II in New Guinea. US Army Colonel Edgar Rothkrug was working as an engineer for the Army Corps of Engineers where they were testing the amphibious tanks ^{[citation needed]}. The story is simple: the warehouse was on one side of the street and the boat launch ramp was on the other. Apparently the Military Police were not watching the speed as well as they should have because cars would speed along that road endangering the men crossing to launch the tanks. Realising that drivers slow down for potholes, Rothkrug had his men pour down concrete to create a raised bump to slow down drivers. It worked exceptionally and since cars did not have seatbelts then, some drivers were actually ejected from the jeeps. Being an invention in the military, the army took the patent for the speed bump but credited the inventor by naming it the "Rothkrug bump" in army manuals ^{[citation needed]}.

The first speed bump in Europe was built in 1970 in the city of Delft in the Netherlands ^[2].

[edit] Road humps in the UK

In the UK, vertical deflection in highways, designed for Traffic calming, is of the following forms:

Road hump is the most common variety which are usually round-topped.
Speed table is a type of hump with a central plateau which is both long and broad. It may include a pedestrian crossing. This type are preferred by some emergency services and bus operators
Speed Cushion is a raised portion of road with a flat top only extending over part of the carriageway width. Cushions can be used singly, in a pinch point, or in pairs or triples.
Rumble strips - Uneven road surface which is now only used in rural areas and retail parks because of the noise.

The Department for Transport defines the regulations for the design and use of road humps ^[3].

[edit] Criticisms

The Association of British Drivers^[4] is critical of speed humps claiming:

drivers are distracted by the bumps, therefore ignoring other hazards such as children.
can impede or slow emergency vehicle access to areas. In 2003, the chairman of the London Ambulance Service, Sigurd Reinton was reported as claiming that delay due to speed bumps was responsible for up to 500 avoidable deaths from cardiac arrest each year. However, this claim has been heavily disputed, with one transport expert claiming the real figure is fewer than 20. ^[5]
increase pollution as traffic travels in a lower gear using signifcantly more fuel per mile.
are a substitute for a lack of enforcement.
Increase noise by both traversing over the bumps and by using more engine revs than normal.
Cause spinal damage^[6] or aggravate chronic backache.

Other criticisms of speed bumps, include: ^{[citation needed]}

Larger vehicles, such as buses, are unimpeded by speed cushions. These cause serious injury to pedestrians during an accident, unlike the modern motor car where pedestrian safety is taken in to consideration, especially for EuroNCAP ratings ^[7].
kill more people than they save, mainly due to the aforementioned delays in providing timely emergency service.
Encourages rapid acceleration and speed increases in certain spots as drivers attempt to make up for time lost slowing down for the bumps. Even between bumps, drivers accelerate and brake harshly.
Speed of traffic around speed bumps is unpredictable increasing danger from excess speed (7%) to one of Failure to judge other persons path or speed at 10.7% ^[8]
Traffic moves to the middle of the road to avoid speed cushions, partially against on coming traffic.
Motorcyclists are forced to move either side of a speed cushion. This means they are either then often running over splippy man hole covers and drains or in to on coming traffic.
Correct operation of anti-lock braking systems is affected, increasing stopping distances.
Similar to motorcyclists, push bike users are forced to avoid the speed cushions. If cyclists hit a speed bump too quickly, but within the speed limit, they are launched in to the air, losing control of their bike.

[edit] Dynamic speed bumps

Dynamic speed bumps are a recent innovation which differ from conventional speed bumps by only activating if a vehicle is travelling above a certain speed. Vehicles travelling below this speed will not experience the discomfort of a conventional speed bump. Dynamic speed bumps may allow the passage of emergency vehicles at higher speeds.

In a design by British company Dunlop Transcalm, a rubber housing is fitted with a pressure valve which determines the speed of a vehicle. If the vehicle is travelling below the set speed the valve opens allowing the bump to deflate as the vehicle drives over it, but remains closed if the vehicle is travelling too fast. The valve can also be set to allow heavy vehicles, such as fire trucks, ambulances and buses to cross at higher speeds. Dunlop Transcalm claim that their dynamic speed bumps reduce or eliminate negative effects of speed bumps such as increased noise and pollution, uneven traffic speed, and impeding emergency vehicles. Each 'smart hump' reportedly costs between £2,500 and £4,850. ^[9]^[10]