Speed choice
Exceeding the speed limit is very common; Percentages of more than 50% are by no means an exception. As many as a quarter of all crashes could be prevented if all motorists obeyed the speed limit.
Why do drivers massively exceed the limit or, in other situations, obey it? Since 2000, safety as motive for obeying the speed limit has been gaining in importance in the
A combination of situational (being in a hurry), personal (excitement seeking), and social factors (adapting to the other vehicles) is mostly the cause of driving faster than permitted. Driving too fast can also go unnoticed because it has become a habit, the vehicle doesn't make much noise, the road image, or the speed limit is not credible.
For more details:
Fact sheet Speed choice: the influence of human, vehicle, and road (pdf)