There is a pretty common perception that speeding is nowhere near as bad as drink driving. If you get caught driving while drunk you won't get much sympathy from most people if you complain about how unfair it is that you got fined for having a high blood alcohol reading while behind the wheel. Yet it seems almost everyone has a story to tell about how they were fined "for going only 20 km/h over the limit, and there weren't even any other cars around", and it's a pretty common view that speeding tickets are just a form of revenue raising for state governments. In Sydney, there are a number of permanent speed cameras. Information about their location is freely available, and there are prominent signs warning motorists of their presence, and yet there are still a lot of people that see them as an insidious plot to raise cash and an infringement of a driver's right to go as fast as they want to.
So, it might come as a surprise to a lot of people that exceeding the speed limit by more than 5 km/h is as dangerous as driving with a blood alcohol level of higher than 0.05%. In a 60 km/h limit area, driving at 65 km/h doubles the risk of having a serious crash (one involving a serious injury or fatality). Driving at 70 km/h increases the risk by a factor of four, and driving at 80 km/h makes you about 30 times as likely to have a serious accident than driving at 60 km/h. In terms of the increase in risk, driving 20 km/h over the speed limit is about as dangerous as driving with a blood alcohol level of 0.15%. If you're a guy, you can achieve this level by drinking about 9 standard drinks in an hour.
The reason speeding is so dangerous is, of course, stopping distances. No matter how good a driver you are, there are other people out on the road as well, and they can do stupid, stupid things. When they do, you need to stop suddenly. Drinking slows the reaction time, which in turn increase the time and distance the car takes to be brought to a halt. When speeding, your reaction time remains the same, but the car travels a greater distance in the time it takes to react to a situation and start to brake. Even then, once the brakes are applied the car more time and more distance to stop once the brakes are applied. This also leads to much greater impact speeds. A car travelling at 60 km/h has a stopping distance of around 25 m. For a car travelling at 70 km/h, when it passes the point at which a car travelling at 60 km/h has stopped, it is still travelling at about 45 km/h. A car originally travelling at 100 km/h will still be travelling at over 90 km/h when it passes the point at which a car originally travelling at 60 km/h would have stopped.
So, when I hear people complaining about the speeding ticket they just got, all I can think is "you should have lost your license". The chances of having an accident during any one particular trip are pretty small, but if you speed regularly then over the course of your life there's a pretty good chance that you'll be involved in a serious accident. I sure hope you don't kill anybody.
Sources:
http://raru.adelaide.edu.au/speed/contents.html
http://www.sdt.com.au/STOPPINGDISTANCE.htm