Stopping Distances - RoSPA's Pedestrian Injury Simulator

Facts : Speed

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Drivers who travel at higher speeds have less time to identify and react to what is happening around them. It takes them longer to stop. And if there is a crash, it is more severe, causing greater injury to the occupants and any pedestrian or rider they hit.

A car’s overall stopping distance from any speed is made up of the driver’s thinking distance (the distance the car travels between the point when the driver realises they need to brake and actually starting to brake) and their braking distance (the distance the car travels from the point when they driver starts to press the brake pedal and the vehicle coming to a complete stop).

Speed increases both the thinking distance and the braking distance. A driver travelling at faster speeds will have covered more ground in between spotting a hazard and reacting to it. The simulator shows how much longer the thinking distances can be at higher speeds.

Speed limits are set to help drivers understand the dangers of each road, and inform them of the legal maximum speed, above which the risks to the driver and other road users are too great to accept.

Facts and Statistics about Speed

Speeding and excessive speed causes thousands of serious accidents and injuries every year.

Inappropriate speed (including exceeding the speed limit and driving within the limit but too fast for the conditions) contributes to 24% of collisions in which someone is killed, 14% of crashes resulting in a serious injury and 12% of all injury collisions. In 2013, 249 people were killed in crashes involving someone exceeding the speed limit (16% of all road deaths) and a further 209 people died when someone was travelling too fast for the conditions.

Approximately two-thirds of all crashes in which people are killed or injured happen on roads with a speed limit of 30 mph or less.

The risk of a pedestrian who is hit by a car being killed increases slowly until impact speeds of around 30 mph. Above this speed, the risk increases rapidly, so that a pedestrian who is hit by a car travelling at between 30 mph and 40 mph is between 3.5 and 5.5 times more likely to be killed than if hit by a car travelling at below 30 mph.

The Simulator and Speed

The simulator allows you to experience and compare the potential effects of different speeds down a residential street, and show you how your choice of speed relates to a possible injury.

The simulator shows how speed increases stopping distances.

At different speeds, the time it takes a driver to respond to a hazard (the thinking time) is the same. However, the distance the car covers during this thinking time increases at higher speeds. The simulator illustrates this.

Speed also increases the braking distance, and even a relatively small increase in speed increases the braking distance by a greater rate. If the speed is doubled then the braking distance is increased by four times.

These two factors mean that even a small increase in speed can extend the overall stopping distance by a large amount, as the simulator shows.

Top Ten Tips to Avoid Speeding

Many drivers unintentionally exceed the speed limit, often without realising it. Modern cars are so powerful and comfortable they give drivers little sensation of their speed – it can be easy to creep above the limit.

Although a driver may not intend to drive above the speed limit, they are responsible for the speeds that they actually drive. Whether by intent or accident, driving above the limit is illegal and can be very dangerous, especially in 20mph or 30mph zones where even a couple of miles per hour extra may be the difference between a pedestrian walking away or suffering a serious injury.

Drivers are responsible for the speeds at which they choose to drive, but there are some simple and practical things drivers who find it difficult to stay with speed limits can do to help themselves: Top Ten Tips to Avoid Speeding.

. Top Ten Tips To Avoid Speeding
RoSPA's practical tips for drivers who find it difficult to stay within the speed limit.

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Produced with the support of the Department for Transport.
Produced with the support of the Department for Transport.
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