The story behind speed bumps

Speed bump, road hump, sleeping policeman – they go by many names but they all serve the same purpose – to slow down traffic.

Your opinion of the speed bump probably depends on your current situation – if you’re a pedestrian crossing a wide road or a parent or grandparent living on a busy street, you may appreciate the cars slowing down, but the moment you get behind the wheel you might inwardly curse as you see a speed bump appear in the road ahead.

So what’s the story about these unassuming bumps in the road – and do they actually do more harm than good?

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The history of the speed bump

Speed calming measures that change the height of the surface of the road were first utilised in the US town of Chatham in 1906, where they raised the crosswalks five inches with flagstones and cobbles; this was received so warmly that on the day it was completed people bought popcorn and settled down to watch as unwary cars jolted uncomfortably over the unexpected hurdle.

By the time Steinbeck’s Grapes of Wrath was published in 1939, humps to slow down drivers were becoming more common. In the book, the main character goes over a hump as he turns a corner; a watchman witnesses the incident and tells him that telling people to go slow doesn't work - but once they hit the bump, they don't forget!

1953 saw Nobel Prize-winning physicist Arthur Holly Compton design a speed bump that is more or less the same speed bump design used across the world, but the UK didn’t adopt this method of traffic calming until the 1980s.

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A speed bump by any other name would still slow the street

Whilst it’s unlikely you’ll ever be stopped short by a road hump pedant, the different designs of traffic calming measure do go by different monikers.

You’d be forgiven for thinking that every bump you have to slow down for is called a speed bump, but actually you’re only likely to encounter these in car parks or private roads. That’s because they’re a lot more intimidating than their brethren; they can legitimately – and often do - reach heights of 10cm from the road surface, forcing you to slow down to as little as 5mph in order to get your car over safely.

The road humps you’ll encounter in your day to day journeys are actually called speed humps, and they usually only require you to slow down to 20mph. Although the Highways Road Humps Regulations 1999 state that these can also reach the dizzying height of 10cm, they’re usually a lot gentler and less likely to do your car a damage. 

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And those road humps that your car can straddle if you hit it at exactly the right spot? They’re known as speed cushions, and they’re designed so emergency vehicles can go over them without slowing down. If you have a large enough car it means you too can probably speed over them too, but just because you can doesn’t mean you should. If you consider them a handy reminder that you might need to pay extra attention to keeping your speed down, you won’t be taken by surprise if there’s a school letting children out as you pass.

Less common are speed tables, which raise your vehicle up for a short way before gently lowering you back to the road surface. They’re less of a shock to the system, but again, take care on these and consider them a nudge to check your surroundings as they’re often used on pedestrian crossings.

And as for sleeping policemen: we’re not really sure where this came from, but sadly it seems to have dropped out of the public vernacular of late – so let’s all just agree that all road humps are allowed to be called sleeping policemen, because it’s just such a wonderfully British phrase.

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How to drive over a speed bump

In order to reduce air pollution, you shouldn’t find yourself slowing down to go over one speed bump, speeding up and then slamming the brakes on again to go over the next one. The time you save doing this is negated by the extra fuel you burn, and as we’ve pointed out before, there’s a reason for the bumps to be there.

However, in order to make the ride more pleasant for all and reduce the wear and tear on your car, you could take physics into account and plan ahead. As you approach the speed bump, brake in enough time to get down to a slow enough speed so you can then accelerate slightly over the bump. Breaking transfers the weight of the car to the front, making the wheels hit the incline harder; accelerating slightly moves the weight back to the rear, giving the car a smoother journey over the bump.

If you can see that the bump ahead is covered in gouges and scratches from other vehicles, proceed even more carefully – not only is this wear and tear a good indication that the bump might not be as gentle as it looks, the uneven surface could potentially damage your car’s wheels, so caution is the word.

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