It was a flippant comment, however, their is a serious point to it. In urban areas where traffic is slow anyway, 20mph or less, stepping out to cross a road is largely at the behest of the drivers. It's not a case of could they stop in time to let you cross, it's more would they stop for you. A driverless car would have no option but to stop or slow down.
On the plus side 20mph zones would be complied with, as would all speed limits on all roads and accident rates would plumet, which is a good thing.
If programmed accordingly it could be impossible (save for an emergency) to park the car illegally, that's going to truly fuck up the school run, another added bonus.