That is wrong. Operator skill is the most important factor in reducing the potential for collisions. Lack of operator skill is the number one cause of collisions.

How much enforcement is enough? I live in a town that has zero tolerance and a ton of traffic cops. People still drive 5-10 over. It would take a constant police presence to eliminate speeding.

Finally, crashes will always occur. You take a risk stepping out of your door. Zero risk is an impossible goal. It is better to focus energies on the area that will do the most good. Increasing the skill level of the driver and the consequences for a mistake is the right approach. Lowering speed limits mainly impacts those who already obey the law.