[mytochar]

While true, unless there are extenuating circumstances (weather, limping car, etc), it's better to drive near the speed limit.

Much of the danger in driving occurs when there's a substantial difference in speed between cars. (I imagine the second most common time there's an accident is when cars are going almost exactly the same speed[1]). Driving 10 under can be very dangerous.

[1] my thinking here is that if you have 2 cars going almost exactly the same speed, but one is sitting in the other's blindspot, then one of them can attempt to change lanes and the other might miss it and suddenly accident.