What is the average stopping distance at 40mph?
No matter how good the brakes and tires are, the laws of physics don't change.
If you double your speed from 30mph to 60mph, your braking distance won't be twice as long, but it will be four times as far.
The following tables are for guidance only, because there are differences between vehicles.The speed at which a driver reacts to a hazard is the most important factor in stopping distances.Under normal driving conditions, very few drivers can get onto the brakes within half a second, and two-thirds of asecond to a full second is more typical.
Australian research shows that young drivers are particularly prone to freeze up with fear at the sight of an unexpected hazard, and their reaction time can exceed two seconds.
When you read the literature for new cars, they only give you the braking distance, not the overall stopping distance.
When the road is icy or covered with snow, or diesel fuel has been spilled, thebraking distance for your vehicle can be as much as ten times further than for dry roads.