[lotu]

On residential streets where you want slow traffic yes. When you have a wide straight road people go fast on it. To prevent that you narrow the road, install curves and bumps. These require to the driver to slow down and be careful, which means they also notice when there are children nearby playing and don't run them over.

[somanyphotons]

In my early 20s I loved the traffic calming curves, it was a really fun challenge to go just as fast as you possibly could through them

[teekert]

Your license should have been taken away, until you'd learn, preferably before you'd kill a child.

[somanyphotons]

Sure, but they didn't, and I didn't harm anyone.

The actual point, is that not every action has the intended consequences. In this case, traffic calming curves do the opposite for a non-zero percentage of people.