How to monetise bus stops with advertising for good has long been a subject of interest to us... As it is to HM Govt.

http://rickwaghorn.co.uk/2013/04/17/alex-aiken-calls-on-government-marketeers-and-comms-professionals-to-be-ruthless-and-germanic-in-their-ad-spend-here-we-go-to-mobile-to-any-bus-stop/