Do bus stop ads really work ?

I was at a tram/ bus stop. Two guys came in a van to change the big poster ads at the stop. They argued for 5 minutes about what the right ads were meant to go at the bus/tram stops around the intersection I was waiting. This made me think that there must be advertising executives that have spent hours deciding what advertising poster goes where (and for how long) at bus/tram stops around Melbourne.
Does advertising work that well that it matters what poster goes where and for how long at bus and tram stops ?

WAG: There is no direct connection, in the sense that no one will answer the question “Why did you buy this product?” with “Because I saw an ad for it at a bus stop.” But if they see a product name on TV a few times, and in a magazine, and once on a billboard, and then also on the bus stop, it helps drive that name recognition into their mind a little bit.

One case here in Auckland, where an advert only on bus stops caused a big brou-haha over advertising standards. Within a day, thousands had seen the ads, and were talking about them. They were later withdrawn.

Not a scientific study into advert on bus stop effectiveness, but I’d say it showed that folk do see the damned things.

I don’t think many people are swayed by advertising anyway, it’s really just awareness. But you can’t go wrong with big posters when you’re standing around right next to it for ten minutes with nothing else to do.