We all know slowing down for a speed bump and then accelerating back to your original speed saps your fuel, but now a recent study commissioned by the UK’s AA motoring group has found out just how bad it really is. Researchers found that a car capable of achieving 58mgp fuel economy when cruising at an uninterrupted 30mph speed would only deliver 31mpg when it’s forced to slow down for a series of speed bumps. Along with the added fuel consumption also come all the other nasties of burning more fuel, namely, increased pollution.

The study found that reducing speed limits to 20mph from 30mph affected fuel consumption and emissions (10% higher), as most engines are calibrated for maximum efficiency at higher speeds. Another group previously found that carbon monoxide emissions are increased by as much as 82% and nitrous oxide levels by 37% on roads with speed bumps.

The ideal solution, researchers say, would be to strictly enforce maximum speed limits and do away with the speed bumps altogether.

What the studies haven’t addressed is the damage to a car’s suspension system, unnecessary brake wear, and the unbearable scrapes to a car’s underbody caused by driving over speed bumps with poorly designed and steep ramps. There’s nothing worse than when driving an ultra-low sports car and hearing a crunch as the front bumper gets a good taste of the road.