Do Speed Bumps Increase Traffic Safety?

"A recent paper purporting to show that speed humps make residential streets safer for children actually shows nothing of the kind. In fact, the study's data can even be interpreted to mean that humps make streets more dangerous.

The study used a database showing when and where 1,600 speed humps were installed on Oakland streets between 1995 and 2000. Ideally, the researchers would have compared accident rates on those streets before the speed humps were installed with rates after -- but they did not. Or they could have compared accident rates on those streets with rates on streets that did not have speed humps -- but they did not, at least not directly.

...Curiously, the researchers found that having a speed hump in front of your home reduces your child's chances of being hit by a car a quarter mile away from your home by the same percentage as they reduce the chances of being hit in front of your home. The study does not say how a speed hump in front of your home protects your children when they are a quarter mile away. This strange finding should have signaled to the authors that something was wrong with their methods."