Speed bump

A speed bump (also known as a sleeping policeman, a kipping cop; in British English a speed hump, road hump (not to be confused with the wider speed hump), speed breaker; in New Zealand English a judder bar; in Hiberno-English a ramp) is a speed-reducing feature of road design to slow traffic or reduce through traffic, via vertical deflection. A speed bump is a bump in a roadway with heights typically ranging between 3 and 4 inches (7.6 and 10 cm). The depth of speed bumps is typically less than or near to 1 foot (30 cm); contrasting with the wider speed humps which are typically 10 to 14 feet (3.0 to 4.3 m) in depth.^[1][2]

Speed bumps can be made of recycled plastic, metal, asphalt or rubber. Speed bumps of various sizes can be placed on a road, from using two four foot or six foot devices on it with a space on either side for avoiding the bump on one side of the car, or connected across the entire road surface.

The use of speed bumps is widespread around the world, and they are most commonly found where vehicle speeds are statutorily mandated to be low, usually 40 km/h (25 mph), or 8 to 16 km/h (5 to 10 mph) in car parks. 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, though in some cases a small cut in the bump allows those vehicles to pass through without impedance.

Contents 1 History 2 In the UK 2.1 Opposition 3 Disadvantages 4 Dynamic speed bumps 5 See also 6 References 7 External links

History

On June 7, 1906, 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".^[3] 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.^[4]

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 and is 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 is 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's width. Cushions can be used singly, in a pinch point, or in pairs or triples.
• Rumble strips are uneven road surfaces which are 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.^[5]

Opposition

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.^[6]

UK news sources reported a cyclist being killed in a crash while attempting to avoid a speed bump.^[7]

Speed bumps in some areas have been removed after protests by local residents. Such protests cite the lack of any consultation as one factor.^[8]

Disadvantages

Local authorities have cited disadvantages to speed bumps:

• The city of Modesto in California, U.S. produced a fact sheet which contains the following disadvantages:^[9]
  • Slow response time of emergency vehicles;
  • May divert traffic to parallel residential streets; and
  • There is a possibility of increased noise and pollution for residents living immediately adjacent to the speed bumps.
• The English town of Eastleigh states the following as disadvantages:^[10]
  • Can cause damage to some vehicles;
  • Can increase traffic noise, especially when large goods vehicles pass by;
  • Signs, street lighting and white lines are all required and may be visually intrusive;
  • Can cause discomfort for drivers and passengers; and
  • Can cause problems for emergency services and buses.
• Drivers are distracted by the bumps, therefore ignoring other hazards such as children; and
• 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^[11] 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.^[12]

In Sweden, an evaluation of spinal stress in bus drivers against ISO 2631-5 required on health grounds^[13]:

• bus drivers to avoid certain streets until the humps were modified; and
• a reduction of the maximum acceptable speed to 10 km/h on one street for drivers encountering 150 humps in a day.

A potential may exist for liability or at least a law suit when a driver damages his car by going too fast over speed bumps.^[14]

Dynamic speed bumps

Dynamic speed bumps differ from conventional speed bumps in that they only activate if a vehicle is traveling above a certain speed. Vehicles traveling 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 one design, a rubber housing is fitted with a pressure valve which determines the speed of a vehicle. If the vehicle is traveling 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 traveling too fast. The valve can also be set to allow heavy vehicles, such as fire trucks, ambulances, and buses to cross at higher speeds.^[15][16]

See also

• Rumble strip
• Speed hump
• Speed table

References

External links

• London Assembly, London's got the hump, April 2004. An examination of speed humps conducted by the London Assembly’s Transport Committee.

Traffic Calming Devices that use Vertical Deflection Rumble strip · Speed bump · Speed hump · Speed cushion · Speed table