SPEED HUMPS (AND SPEED BUMPS)
The following information on speed humps, a very painful and ineffective solution to the problems of excessive vehicle speeds, was acquired by Roger Lawson when he was running a campaign against them in the London Borough of Bromley. He is happy to advise anyone on this subject - use the Contact page to get in touch. This and the linked pages probably contain the most comprehensive analysis on the internet of the problems caused by speed humps.
Speed humps (sometimes known as bumps), are a very painful approach to road safety and there is widespread opposition to their use. For example a group of local residents decided to oppose the traffic calming scheme installed in Watts Lane/Manor Park Road in Chislehurst (Bromley). In this case there was little need for an aggressive approach to speed in the road, as there were very few accidents anyway. This road was used as a local distributor route (in fact previously it had been classified as a "B" road) and there were few alternative routes that traffic could take.
What are the objections to speed humps?
1. They are uncomfortable, or indeed painful to many people. As Transport Research Laboratory Report 417 makes clear, speed humps only work when they are uncomfortable. Unfortunately, many people who suffer from medical conditions such as back problems (one of the most common medical complaints), recent abdominal surgery or other disabilities find them extremely painful. For more information and reported experiences of medical problems go to Speed Humps and Medical Conditions.
2. They are a very blunt instrument. In fact, different vehicles respond very differently with heavy vehicles such as HGVs, buses and other public service vehicles being particularly prone to discomfort unless humps are traversed at very low speeds. It is simply impossible to design a speed hump that is negotiable comfortably at a reasonable speed by all vehicles and which is not painful to the occupants. Many bus operators object to humps because of complaints from their drivers and passengers, and also because of damage to their vehicles. As a result, it is generally recommended that only “cushions” that buses can straddle are used on bus routes, but that is not a panacea because vehicles parked on the route often force bus drivers over humps.
3. Speed humps have been known to cause accidents and injuries. For example, there was the case of the motorcyclist who hit a speed hump in Wood Lane, Isleworth in 2001 at much less than 30 mph. He was ejected from the bike and suffered serious injuries from which he is now paralyzed from the waist down. Several cases of broken backs have been reported in Scandinavia, including one in Norway where a bus passenger was injured when the bus went over a speed hump which was hidden by snow. A similar example was that of Neil Price of Kendal, Cumbria who was riding in the back of a bus when it went over a speed hump - the result was two broken vertebrae and spinal damage resulting in paralysis. Another case was in the London Borough of Sutton in 2004 where a police car spun off the road and hit a tree injuring PC Stephen Poole who had to be rescued from the smoke-filled vehicle by a colleague, after it hit a speed hump. The Daily Telegraph published two letters on 18/3/2006 giving the following examples: A speed hump was installed in Swindon outside a fire station in the early 1970s. Within a few days a woman cyclist rode out of the station, turned left and struck the hump at an angle. She fell off and was killed by a passing motor vehicle. A speed hump was also installed at Guys Hospital in the 1980s. Soon after an accident victim with spinal injuries was being brought to the hospital via ambulance. When it crossed the hump, the result was a complete spinal cord injury and the patient was left as a permanent paraplegic. In both cases the humps were removed soon afterwards. A similar case was reported to the letter to the Daily Telegraph on 17/6/2006 when "K.P." said that his father, a retired policeman, drove over a road hump quite slowly in the East Midlands and his neck was broken - he spent the rest of his life paralysed.
There are also the examples of Anja Szkodowski in Bromley who was severely injured in 2005 as a direct result of hitting a speed cushion while cycling (see: Old-Hill-Accident) and of entrepreneur Richard Branson in 2016 which is documented on our blog here: Branson Accident
4. They frequently cause damage to vehicles. Even at normal speed levels vehicles can be damaged by humps, but it is legally very difficult to make a claim against a local authority as a result. This problem particularly affects older, heavier vehicles or those with low ground clearance. In addition there is the concern that they cause damage to tyres which can result in catastrophic failure of the side walls at high speed (what is commonly known as a "blow-out") - unfortunately of course such incidents typically take place some time later and after accumulative damage from humps so it is impossible to attribute them to particular humps at particular times, but it is alleged that this kind of damage is becoming much more common.
5. Speed humps cause atmospheric pollution and noise. This arises from the speeding up and slowing down of traffic between the humps (see TRL report No.482 on this subject). For example, TRL reports a 59% increase in CO, about 50% increase in HC and about 25% in CO2 from petrol catalyst vehicles averaged over all types of traffic calming measures, with even higher numbers over more "severe" measures such as speed bumps. In addition the use of bumps and cushions seems to encourage the use of larger vehicles which are more polluting.
In January 2008, research commissioned by the AA showed that speed humps cause fuel consumption to rise substantially. Researchers at the Millbrook Proving Ground found that while a car capable of over 58 mpg when driven at a steady 30 mph, delivered only 31 mpg when it had to slow down to negotiate speed humps and then speed up again. Carbon dioxide emissions changed similarly in proportion. The AA claims that this research backs up the reports previously published by TRL which showed carbon monoxide emissions increased by as much as 82% and nitrous oxides levels by 37% on roads with speed humps. AA president Edmund King said “Humps are a crude, uncomfortable and noisy way of slowing people down and this research has shown they are also environmentally damaging”.
As confirmation for the above a study in 2016 by Imperial College, London also found high levels of pollution from road humps – indeed higher than from other forms of traffic calming (see the Daily Telegraph on the 11/6/2016 for a fuller report on this). For example they got 47% more particulates and 64% more NO2 from a petrol car when driven over humps, and even higher figures for diesel cars.
It is also alleged that speed humps increase metallic air pollution particles by up to three times resulting in lowered resistance to coughs and colds - see this article published in 2020: London-Throat.
Humps can also cause increased noise from heavy vehicles, and in extreme cases, subsidence of the road and buildings alongside due to the ground pressure waves that are created. For more information on the latter, see: Speed Humps-Vibration-Noise.
6. Speed humps are a major problem for emergency vehicles. Ambulances and fire engines suffer difficulties from speed humps. Apart from the major discomfort to ambulance passengers, they also delay response times substantially. This can be as much as 10 seconds per device, and in a study done in the USA it was calculated that more deaths would arise from delayed arrival of ambulances than could ever be saved by any possible accident reduction. For more information on this, go to the following page: Speed-Humps-Ambulances. For more information on the impact of traffic calming devices on emergency services, it is worth studying a presentation by former fire chief Les Bunte that was given to the 2006 American Dream Coalition conference in Atlanta: Bunte-Traffic-Calming. Also look at the Four Hills Study mentioned below for calculations on a specific scheme.
7. Speed humps create additional road maintenance costs. This is because the road surface before and after a hump tends to develop potholes after a couple of years. This results in much heavier maintenance costs than normal. In addition to fully resurface the road it is often necessary to remove and replace the speed humps, which also adds to the cost.
8. Do speed humps actually reduce accidents? In reality there is very little evidence to support this. Where accident reductions have occurred it can mainly be attributed to diverting traffic (which can be as high as 50%). Most accidents are not caused by speed but by careless driving, or a multitude of other factors that are not affected by speed humps. In London where over the last few years there has been a lot of expenditure on speed humps in some boroughs, there is no correlation between high expenditure on humps and accident reduction, i.e. the boroughs who spent money on other road safety measures did as well or better in accident reduction. Speed humps are a very poor accident prevention mechanism in terms of cost effectiveness, in comparison with other possible accident prevention approaches. For some real data on the effect of speed humps on accidents in a road in the London Borough of Bromley, go to this page: Speed-Humps-Effects. Another very useful study was by Michael J. Cunneen of the impact of speed humps in Albuquerque which is available on this page: Four-Hills-Study. Both these reports suggest that any beneficial impact is less than 5% and may actually be non-existent.
9. Main types of humps. The main types of speed humps are round or sinuisoidal humps, cushions, or speed tables. These are shown in the photographs below.
10. Common questions and answers on speed humps in the UK:
A. Do road users have to be consulted on their installation? For a traffic calming scheme, road users, or bodies that are known to represent them legally have to be consulted. In addition, details would normally be published in a local paper (that which is used to publish public notices). There will usually be small signs placed on the street and a consultation leaflet circulated to local residents. However, it is quite likely that most road users will not be aware of such notices. In reality, the views of local residents may take priority over road users - indeed road users views are likely to be ignored. Surely what matters is the good of the community as a whole. For individual humps or speed tables, there are no legal obligations for consultation.
B. What are the regulations on hump size and spacing? Most speed humps are now constructed to be 75 mm high, although legally they can be higher. There are also government guidelines on the shapes of humps and their spacing. Go to the following page for full details on the legal background to speed humps and traffic calming: Legal-Basis-Traffic-Calming.
C. Is reducing the number of humps by increased spacing a good idea? No. Increasing the spacing simply causes vehicles to speed up and slow down in between them.
D. What do they cost? About £2,000 upwards for a speed hump, and maybe £10,000 for speed tables which are more complex and larger. A typical traffic calming scheme can easily cost £100,000 in a fairly short stretch of road.
E. Why are speed tables or cushions used sometimes? Speed tables are used at junctions (a hump cannot normally be near a junction) or under zebra crossings or mini-roundabouts. Cushions (a euphemism for split humps) are used where buses or other PSVs are likely to use the route (speed humps are simply too uncomfortable) - such vehicles can in theory straddle a cushion, but in reality often the presence of parked cars alongside stops this. Also, the use of three across cushions which is quite common on wider roads encourages people to drive down the centre of the road, which is dangerous. Cushions are good in theory, but bad in practice.
F. Are there alternatives to using speed humps to cut dangerous traffic speeds, e.g. near known hazards? Yes. At junctions (which are often the location of many accidents), mini-roundabouts or speed tables can be used. The former do tend to result in minor vehicle damage accidents however. The latter can be more comfortable than speed humps, but still very effective at cutting speeds. One very effective and relatively low cost approach is the use of speed display devices or variable message signs (ones that display a vehicles speed and remind the driver if they are over the speed limit, or warn of particular hazards). Other alternatives are improved signage (e.g. hazard warning signs, speed limit repeaters, "slow" signs), "gateway" treatments of various kinds including width restrictions, rumble strips, and other devices. As to which is most appropriate depends on the nature of the road and the hazards present in it. In fact, it is usually cheaper and more effective to make minor changes to road markings, curb lines, improve sight lines and signage to tackle particular road safety problems, although unfortunately putting in speed bumps is often seen as a cheaper and simpler option (they require less thought) than really tackling the source of accidents in a proper manner.
G. Why do local residents sometimes vote for speed humps? Firstly because the council normally doesn't offer them any alternatives. Secondly because of the selfish desire to encourage traffic to divert elsewhere, which results in someone else suffering from the noise and pollution.
H. Are speed cameras an alternative to speed humps? In most cases no. Speed cameras are very expensive (up to £50,000 each) but are also only effective on a very short stretch of road - people quickly learn where they are, slow down before and speed up afterwards. Therefore, they are best positioned at accident black spots. Obviously the "running" costs of a speed camera are also much higher. Speed display devices are generally more effective and lower cost than speed cameras and are therefore always a better alternative.
I. Who pays for them? A silly question - you do of course, out of taxes. However sometimes, they are funded not from local council budgets but from funds provided by other bodies (e.g. Transport for London in London - a part of the GLA which is partly funded by local London councils and from central government funds).
J. What is the experience in other countries? For information on the legal status and objections to speed humps in the USA, go to Speed-Humps-USA.
Summary. For a more extensive discussion of the subject of speed humps, click on the following: Objections-to-Speed-Humps, which is a pdf document which was submitted to the Greater London Authority Transport Committee Inquiry in October 2003. For a report submitted to the same Inquiry by the London Ambulance Service go to LAS-Report.
In 2008, a petition was launched to remove speed humps from Watts Lane and Manor Park Road in Chislehurst (London Borough of Bromley) - installation of humps on that road prompted the research documented on this web page. See Speed-Hump-Petition. The results of the petition demonstrate how most members of the public oppose the use of humps.
Note that the London Borough of Bromley adopted a policy that stopped the installation of more speed humps which can be recommended to all local authorities. This policy was “a preference for non-vertical deflection traffic calming schemes”, i.e. anything but speed humps (this avoids the legal problem with an absolute prohibition).