Speed Humps

Speed humps have a short rounded top which is typically 75mm high.

The ramps either side are painted with white arrows to make them more obvious to motor vehicle drivers.

The aim of the speed hump is to slow motor vehicle traffic to a safe speed, as the ramps become uncomfortable for vehicle drivers if they are driven over too fast.


  • Buses, cyclists and emergency vehicles may need to slow down
  • Bus companies normally oppose speed humps
  • Some motor vehicle traffic is likely to transfer onto alternative routes, potentially causing a problem somewhere else
Speed hump with car


  • Speed humps are used on residential roads or busy pedestrian areas
  • Shouldn't be used on bus routes

There's also some general restrictions to note for all schemes


  • May cause traffic to divert to other routes
  • Speed humps could create noise and vibration which is heard and felt in residences nearby. A greater distance between speed humps and residences will reduce this problem.


  • More effective than speed cushions and horizontal treatments
Speed hump close up


Generally, vertical treatments - such as speed humps - are expected to reduce accidents by around 44%.

Motor vehicles are likely to travel at around 15 mph over a speed hump. If there's a series of speed humps, vehicles are likely to travel at 20 mph between them.

Speed humps do not slow motor vehicle traffic as much as speed tables, however they are more effective than speed cushions.

Reducing motor vehicle speeds increases safety because:

  • The vehicle has travelled less distance before the driver can react to a hazard
  • Breaking distance is reduced, so the vehicle can stop more quickly before a hazard
  • A slower moving vehicle will exert less energy on occupants as the vehicle rapidly changes speed on impact (crashes)
  • A slower moving vehicle will transfer less energy to a pedestrian in the event of a collision
Cost:   £12,000 - 20,000 (four humps)

This scheme requires a Traffic Regulation Order

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Likely motor vehicle speeds when travelling over a speed hump are taken from TRL report 186 (Webster & Layfield, 1996). The research was based on Local Authority data at thirty-three 75mm high round-top humps from around England. All sites had a 30 mph speed limit except four, which had 20 mph speed limits. The speeds between humps is based on an average separation of 90m between the devices, with an 85th percentile speed of 26mph. Overall, the quality of this study is very poor . there is no methodological detail given, including any use of control sites, or before/after data collection periods. In the absence of other, specific analysis on round-top humps, this paper is used as a guide for effects on speed.

44% reduction in accidents is taken from Mountain, Hirst and Maher (2005). The study calculated accident reductions from various different types of traffic calming measures. Local authority and police data were used throughout Great Britain from 150 speed management schemes on 20 mph roads. Analysis is particularly strong, with correction for change in flow, accident trend and regression to mean.

Factors associating reduced motor vehicle speed to road safety are based around Wilson et al. (2010), who note the large body of research consistently linking casualty rate with speed (e.g. TRL 421).


Mountain, L., Hirst, W., Maher, M. (2005) Are speed enforcement cameras more effective than other speed management measures? The impact of speed management schemes on 30 mph roads. Accident analysis and prevention 37 pp. 742 . 754.

Taylor, M., Lyman, D., Baruya, A. (2000) The effects of drivers - speed on the frequency of road accidents (TRL421). Transport Research Laboratory. Crowthorne, UK.

Webster, D. & Layfield, R. (1996) Traffic calming - road hump schemes using 75mm high humps (TRL186). Transport Research Laboratory. Crowthorne, UK.

Wilson, C., Willis, C., Hendrikz, JK., Le Brocque, R., Bellamy, N. (2010) Speed cameras for the prevention of road traffic injuries and deaths (Review). The Cochrane Collaboration. John Wiley & Sons.

Winnett, M. & Wheeler, A. (2002) Vehicle-activates signs - a large scale evaluation (TRL548). Transport Research Laboratory. Crowthorne, UK.

Also Consider:
Speed Cushions
A speed cushion is a short, raised, rounded device, normally in the centre of a road lane. Speed cushions are designed to be slightly wider than a car, so car drivers need to slow down and drive over the centre of the speed cushion to reduce discomfort.
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Road Narrowing
Road narrowing simply reduces the width of the road. This could be achieved in a number of ways, however the technique normally used in Bristol involves extending the curb at a junction entrance with a bollard on each side.
Read more > >
Single lane chicanes require one direction of traffic to give way to oncoming vehicles. The chicane normally consists of a raised curb and bollard in one half of the road, with a sign to explain the traffic priority.
Read more > >
Speed Table
Speed tables are a raised section of road, with a ramp on both sides. The ramps are painted with white arrows to make them more obvious to vehicle drivers.
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Speed Cameras
Speed cameras photograph vehicles which are travelling over a certain speed. This is usually around 10% over the speed limit. Speed cameras use a radar device to detect the speed of passing vehicles.
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Vehicle-activated Signs (VAS)
VASs are an electronic sign which only become visible when approaching vehicles are exceeding a certain speed.
Read more > >
Pedestrian Refuge Island
A refuge island is a raised section of pavement between two lanes of traffic moving in opposite directions. The Islands normally have yellow and white plastic bollards with a blue arrow to remind drivers to keep left.
Read more > >
DIY Streets
DIY Streets
DIY Streets is a concept developed by Sustrans which encourages communities to generate ideas for the improvement of their street. The concept aims to make the street less car dominated, and more community focussed.
Read more > >
Community Speed Watch
Community Speed Watch
Community Speed Watch is a scheme to allow volunteers to monitor the speed of passing vehicles using a hand-held speed detection device.
Read more > >
Change Lane Markings
Change lane markings
Peripheral hatching or removing the centre line can reduce the feeling of space motor vehicles have, which may help to reduce their speeds.
Read more > >