The traffic management people are reluctant to put zebra crossings on roads like PV in the immediate vicinity of national rail stations, because at peak times there's a long and steady stream of people and traffic will never get the chance to advance without breaking the law, causing back-ups. Plus, realistically you'd need two, and that would be a nightmare.

At least, this is what they said at Hornsey, where I used to live, and I can see the argument. I'm not that anti-car!