Do you know how to spot a taxi cab in Japan ... There ares some obvious signs like little light at the top of the roof and name of cab company on the side. But, one distinguishing feature of Taxi in Japan is "Green License Plate".
Taxi must be licensed by the government and when the cab and cab driver is licensed, they receive green license plate. If you get on the taxi cab with white license plate, it is an unlicensed cab. It is called SHIRO-TAKU (White Taxi) and it is illegal.
That is one of the reason why you see no UBER or LYFT in Japan. You cannot operate Taxi or Ride Share without government license and the fares are highly regulated as well. No you know how to spot a taxi cab in Japan.
Japanese-Online Blog: http://en.bloguru.com/japaneseonline/