On the point of signage, the photo below is kerb-side at London Gatwick (South Terminal) - our most regularly-used airport. I'll leave it to you to guess what most people in that vaguely signed No Smoking area are doing ... as they do all the time, and with no enforcement by the Airport.

The intention is to avoid smoke affecting people using that yellow-edged archway into the multi-storey car park and Hilton entrance.