State transportation departments and transit agencies have many opportunities for generating revenue from advertising. A variety of interior and exterior spaces can be sold for advertising purposes. State and local agencies can charges fees for billboards along highways, sell advertising space in bus stops and metro stations, put advertisements on buses and transit vehicles, paint advertisements on benches and sell advertisement space at rest areas. Although the opportunities for revenue are plentiful, some may be concerned that too many advertisements can blight a highway or building.