Americans in London

A bloke is showing two young American girls around London and they come to a crossing.

He presses the button and the pedestrian signal goes 'beep-beep-beep-beep...'

"What's that for?" asked one of the girls.

"Oh that's just to let the blind know that the lights have changed" said the bloke.

"My God" she said shocked "in the States

Spoiler:

we don't even let them drive..."