Transport

The risk of injury increases exponentially with impact speed. A crash at 30mph involves a lot more energy and destructive potential than a crash at 20mph.

Driving faster not only lessens drivers’ chances of being able to stop in time to avoid hitting someone or something. It also means if they can’t stop in time, they will hit with greater impact. The greater the impact, the greater the chances of causing serious injury or death.

A vehicle travelling at 20mph (32km/h) would stop in time to avoid a child running out three car-lengths in front. The same vehicle travelling at 25mph (40km/h) would not be able to stop in time, and would hit the child at 18mph (29km/h). This is roughly the same impact as a child falling from an upstairs window.

The greater the impact speed, the greater the chance of death. A pedestrian hit at 30mph has a very significant (one in five) chance of being killed. This rises significantly to a one in three chance if they are hit at 35mph. Even small increases in speed can lead to an increase in impact severity.

Brake the Road Safety Charity

#SpeedDown

Speed and stopping distances don’t increase at the same rate. Small increases in speed result in bigger increases in stopping distances.

Stopping distances include the distance travelled while the driver notices a hazard and applies the brakes (thinking distance), and while the vehicle comes to a full stop from its initial speed (braking distance).

The stopping distances shown here are based on a reaction time of 0.67 seconds, which assumes the driver is alert, concentrating and not impaired. Driving when tired, distracted or impaired significantly increases reaction times, so the thinking distances should be regarded as minimums.2

The braking distance depends on how fast the vehicle was travelling before the brakes were applied, and is proportional to the square of the initial speed. That means even small increases in speed lead to significantly longer braking distances. Braking distances are much longer for larger and heavier vehicles, and in wet or icy conditions.3

Technology such as anti-lock brakes and stability control are designed to enable greater control over the vehicle, not shorten stopping distances. There may be a very small reduction in braking distance with modern technology, but not enough to significantly affect your overall stopping distance.4 Whatever technology a vehicle has, the basic fact remains that the faster you drive, the longer your stopping distance, and therefore the less chance you have of stopping in time in an emergency.

Brake the Road Safety Charity

#SpeedDown

Speed is a critical factor in all road crashes and casualties.

Driving is unpredictable and if something unexpected happens on the road ahead – such as a child stepping out from between parked cars – it is a driver’s speed that will determine whether they can stop in time and, if they can’t stop, how hard they will hit.

Reducing and managing traffic speeds is crucial to road safety.

Breaking the speed limit or travelling too fast for conditions is recorded (by police at crash scenes) as a contributory factor in almost one in four (23%) fatal crashes in the UK.1 This is arguably a gross underestimate, because whether or not a vehicle is judged to have been speeding or going too fast for conditions, the fact it was involved in a collision means it was going too fast to have stopped in time. In this way, speed is always a contributory factor, albeit often in combination with other causes: no one was ever killed by a stationary vehicle

Brake – the road safety charity

#SpeedDown

People speed for a number of reasons:

• because they are in a rush to get somewhere,
• because they are unaware of the speed limit,
• because they enjoy driving fast,

and for many more reasons besides. But there’s no excuse for speeding – it’s a major factor in many road crashes, and the faster a vehicle is travelling, the greater the amount of energy transferred in a crash, and the higher the likelihood of serious injury or death.

View the no need to speed explanimation video showing the risks of speeding, with TRL academy director Richard Cuerden.