Yellow Cab, Tucson, Ariz., is part of the largest taxi cooperative in the western United States. Yellow Cab s drivers are also shareholders, making the taxi company the largest driver-controlled taxi fleet in the United States. Maybe among the most recognizable taxicabs, other than London s black cabs, Yellow Cab companies are in almost every large metropolitan area in the United States. The cab company was the first to implement computerized dispatch in 1989. The dispatch system is constantly being upgraded to insure that it maintains a high standard of efficiency. Yellow Cab drivers are properly licensed with the department of transportation. Yellow Cab does a complete background check as well as random drug testing to insure driver safety and reliability. Some of the services Yellow Cab offers include airport service, medical and social visits, out of the town trips, shopping malls, grocery shopping and tours of the area.