You take your life in your hands on my local zebra crossings here on the steppes of Croydonia. That's motor vehicles though. It's a battle of wills with the driver who will do everything in their power not to stop for a few seconds. It's a little bizarre, I have driven a car and it's not that hard to slow down to a halt for a few seconds and then resume your journey. It doesn't really qualify as exertion. The irony is, this will often happen in sight of a line of traffic, so they're not actually getting anywhere. Late at night, when the police are in bed (7pm as far as I can tell), discretion is the better part of valour and it's best not to assume that a zebra offers any protection. I did nearly have my nose removed by a motorscooter the other day on Portland Road. Idiot had stopped behind a car while I crossed, but decided that it was holding him for too long, so he scooted around the car and carried on across the crossing regardless of the fact that I was about to be occupying the same space.
Cyclist, yeah, they're annoying when they assume that zebras don't apply to them, and that the pedestrians crossing at a green man have similar properties to neutrinos, and sadly this habit does seem near ubiquitous in central London, which doesn't do much for our popularity.