As one of the 3 public transport tools (taxi cab, bus, metro), taxis covers the largest group of public audience. Even nowadays in many cities, the taxi cab company still use the old fashion signs showing only the letters "TAXI", or a light box to show some static advertising pictures - it is widely seen. In China, the situation is a little different as some taxi cab companies use the Advertising LED Display to show some rolling messages of advertising which is not impressive at all.

It is such a huge waste because the taxi cabs are such good public advertising media in the modern cities! 

the factors of led display signs' technology and cost are restricting the development of the led taxi video advertising idea. if we'd let the led signs have the video advertising capability, the resolution of the Taxi Top Sign must be high.