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Speed Bumps

Do speed bumps make the roads any safer?

Speed bump road sign

As we discovered in a 2016 survey, inventions such as speed bumps are not exactly beloved. While effective when properly used, traffic calming measures have been accused of increasing exhaust fumes from braking cars, slowing down emergency vehicles and angering residents. So are they really effective? What's the point of speed bumps exactly? Are we stuck with them? And are there any decent alternatives?

Do speed bumps work?

Traffic calming measures such as speed bumps are designed to force drivers to slow down in areas where speeding might be particularly dangerous - especially to children.

Traffic calming first appeared around 1906 in Chatham, New Jersey, when the average speed of an automobile had reached 30mph. In 1953, a physicist named Arthur Holly Compton invented traffic control bumps’ - pretty much the rubber speed bumps we know and love today - to slow down cars whizzing past his university. It wasn't until 1970 that the first speed bump appeared in Europe, and speed humps finally made their way to Britain in 1983.

The most common - and controversial - types of inhibitor on UK roads include:

  • Speed bumps: Designed by Compton, usually made of plastic or rubber and clearly marked with paint. According to UK law, they can be as high as 100mm, so that a car has to slow down to 5mph to navigate one without damage. Because they need such a significant speed reduction, they're most often used in parking lots, private roads and in some residential areas.
  • Speed humps: Large bumps that span the entire width of the road. They look more like a feature of the road itself than speed bumps do, as they're covered in asphalt or tarmac. They also have a maximum height of 100mm, but they're usually not as tall as speed bumps. They’re often used in residential areas but they're not suitable for bus routes.
  • Speed cushions: Essentially speed humps that have been broken up into discrete parts. They look like short rectangular lumps in the road that come in twos or threes, depending on the width of the road. Because they're broken up, emergency vehicles; with their wider axles; can pass over them without slowing down.
  • Speed tables: Elongated road humps that taper up from road level to a flattened top over a longer distance. They can be used at a junction or to form a pedestrian crossing. And they're easier for heavier vehicles to get over.
  • Chicanes: Artificially constructed bends that make the road into a snake-like shape. Drivers have to reduce speed to navigate the curves.

Successful speed limits should be self-enforcing through both good road design and clear signs. Traffic calming measures like humps and bumps can help enforce lower speed limits thereby making it less likely that people get killed in road accidents. In fact, the World Health Organisation reported in 2015 that Britain's death rates from transport accidents was the lowest in the world.

However, critics point out that speed bumps have a number of unintended consequences. Some traffic may transfer to other roads to avoid the humps, moving the problem rather than solving it. And because because drivers can't stick to a steady speed, the extra acceleration and braking caused by speed bumps can contribute to local air pollution.

Are speed bumps the only way to calm traffic?

No. Many factors contribute to the increased road safety we’ve enjoyed over the years, including road design, vehicle design, driver education and enforcement. The right speed bump in the right place may improve safety but that doesn't mean all speed bumps make the road safer wherever they're put. While it should never be at the expense of road safety, the removal of some speed humps in cities could help improve flow and reduce emissions.

In any event, these kind of road safety debates are likely to continue. We'll have people arguing about speed humps, bumps and speed cameras and we may even hear calls for removing road markings from roads altogether.  However, as the strange case of the speed bump that isn't there demonstrates, you never know what innovations the future may hold.