Many drivers are comfortable going 5, 10, or even 20 mph over the speed limit without thinking much about the risk. But speed changes the outcome of a crash far more than most people realize.

Think of it this way. The force of a crash at 65 mph is roughly comparable to driving a car off the roof of a 12-story building and hitting the ground. No one would ever do that on purpose, of course. But the comparison is a reminder of just how powerful crash forces become at higher speeds.

The point is not to make drivers afraid to get behind the wheel. It is to reinforce respect for the forces at work when a vehicle is traveling at speeds the human body simply was not built to handle on its own.

A Little More Speed Makes a Big Difference

Imagine hitting a fixed object, like a fire hydrant or lamp post, at 25 mph. That may not be fatal, but the damage to the vehicle would still be serious. Even at that speed, a 4,000-pound vehicle carries tremendous force.

Now increase that speed to 35 mph. It may seem like the crash would be only 40% worse because the vehicle is moving 40% faster. But it would actually be almost twice as severe.

That is because the crash force increases exponentially with speed. At 50 mph, the force is four times as great as it is at 25 mph. At 75 mph, it is nine times greater.

Higher Speeds Also Raise Crash Risk

In 2006, the average driver had a 5% chance of being involved in an accident. A study presented at the University of California, Berkeley found that for every 1% increase in speed:

• Crash risk increases by 2%

• Serious injury risk increases by 3%

• Fatality risk increases by about 4%

Driving faster than the surrounding traffic can make things even worse. The same study found that driving 80 mph on a road where traffic is moving at 70 mph increases the chances of:

• A crash by 31%

• A crash involving injury by 49%

• A fatal crash by 71%

The Bottom Line

Speed limits are there for a reason. Obey posted limits, adjust for weather and traffic conditions, stay alert, and leave plenty of space between your vehicle and others on the road.

Even a little extra speed can turn a close call into a much more serious crash.