A speed bump (in British English a speed hump, road hump or sleeping policeman) is a velocity-reducing feature of road design to slow traffic or reduce through traffic. A speed bump is a bump in a roadway with heights typically ranging between 3 to 4 inches (7 to 10 cm). The length of speed bumps are typically less than or near to 1 foot (30 cm); whereas speed humps are longer and are typically 10 to 14 feet (3 to 4 m) in length.
The use of speed bumps is widespread around the world, and they are most commonly found where vehicle speeds are statutorially mandated to be low. 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. Speed bumps can also pose serious hazards to motorcyclists and bicyclists if not easily noticed.
On June 7
, The New York Times
reported on an early implementation of what might be considered speed bumps in the U.S. town of Chatham, New Jersey
, which planned to raise its crosswalks five inches above the road level: "This scheme of stopping automobile speeding has been discussed by different municipalities, but Chatham is the first place to put it in practice".
The average automobile's top speed at the time was around 30 mph.
According to a publication by the Institute of Transportation Engineers, the first speed bump in Europe was built in 1970 in the city of Delft in the Netherlands.
Road humps in the UK
In the United Kingdom, vertical deflection in highways for the purpose of traffic calming
typically takes one of the following forms:
- A road hump is the most common variety which are usually round-topped.
- A 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
- A 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 are an 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.
Opposition to speed bumps
After complaints from Derby
residents, 146 speed bumps were removed from streets at a cost of £ 460,000. Similar incidents have been reported elsewhere in the UK.
Reports have been made of cyclists being killed due to speed bumps in the UK.
Speed bumps in some areas have been removed after protests by local residents. Such protests cite the lack of any consultation as one factor.
have cited disadvantages to speed humps:
- The city of Modesto in California, U.S. produced a fact sheet which contains the following disadvantages:
- Slow response time of emergency vehicles;
- May divert traffic to parallel residential streets;
- There is a possibility of increased noise and pollution for residents living immediately adjacent to the speed humps.
- The British town of Eastleigh state the following as disadvantages:
- Can cause damage to some vehicles;
- Can increase traffic noise especially when HGV’s pass by;
- Signs, street lighting and white lines are all required and may be visually intrusive;
- Can cause discomfort for drivers and passengers;
- Can cause problems for emergency services and buses.
- Drivers are distracted by the bumps, therefore ignoring other hazards such as children;
- Humps can impede or slow emergency vehicle access to areas.
Other sources argue that speed bumps:
- Increase pollution as traffic travels in a lower gear using significantly more fuel per mile;
- Are a substitute for active enforcement;
- Increase noise by both traversing over the bumps and by using more engine revs than normal;
- Cause spinal damage or aggravate chronic backache.
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. He later denied the statement.
A potential may exist for liability or at least a law suit for when a driver damages his car by going too fast over speed bumps.
Dynamic speed bumps
Dynamic speed bumps differ from conventional speed bumps in that they only activate 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.