The energy that has to be dissipated to stop a car, called kinetic energy, increases exponentially as the square of speed. So the difference between 30 and 35mph is only a 16 per cent increase in speed, but it's a 36 per cent increase in kinetic energy, which is one of the key factors in stopping distance.

Stopping distance is affected by a number of factors, including load, condition of the road surface, tyres, brakes, driver skill and design and type of vehicle.

It doesn't matter how good a car's engineering and brakes are, there is nothing they can do 

Attitudes to speeding

• 84% of people disapprove of speeding yet 69% do it. 
• Over 70% of drivers in one study admitted to speeding (Stradling) and in other studies (Webster & Wells) the figure was 85%. 
• TNS Survey results show what we really think of our other half's driving - and many of us are scared and angered when our partners speed. 
• The study reveals that among passengers over 60% believe that driving too fast increases the chances that their partner will crash. And emotions run high: 
• • 24% have felt angered by their significant other's speeding, which they think is 'irresponsible and stupid'. 
  • 20% are scared, and concerned that they and the driver could be killed or injured. 
  • 14% worried about the safety of other road users. 
  • 25% admit to pressing on an imaginary foot brake. 
  • Only 1% wanted their partners to drive faster.  

Key statistics

• You are more likely to kill a pedestrian driving at 40mph than 30mph. 
• Specifically, if you hit a pedestrian while driving at 20 mph, the pedestrian has a 95% chance of survival. 
• If you hit an adult pedestrian while driving at 30mph, the survival chance is 80%. But if you hit a pedestrian while driving at 40mph, the pedestrian's chances of dying rises to 90%. (this lowers to 80% for a child).  

General

• Every driver can make a difference just by slowing down a few miles per hour and observing speed limits. 
• Excessive speed is a contributory factor in over 1,000 deaths and over 38,000 injuries every year. 
• You are not as safe as you thought - car drivers and passengers account for most road deaths. 
• Nearly ten people die every day on Britain's roads. 
• Two out of three crashes where people are killed or injured happen on roads where the speed limit is 40mph or less. 
• Just over half (53%) of drivers break the 30mph speed limit. (Vehicle Speeds Great Britain). 
• The law of physics dictate that the higher the speed at impact, the more energy must be rapidly absorbed by hard metal, soft flesh and brittle bone.