The target audience for billboards depends on where the billboard is placed. So for instance if it was placed near a train station it would be for the general workers. If a billboard was placed in a shopping centre it would be for the shoppers and the shop workers. If the billboard was placed on a road sign it would be for the truck drivers, workers or people going into the area. Back of buses is another area where billboards can be found. The audience for that area is workers or bus drivers. Out of those general locations I think train stations would be the best place to place a billboard because a promotional billboard I think is best placed in a train station because you have people going to and from areas.