some comands that are needed in a taxi:
Driver step on it.-- for a fee the taxi driver should haul ass.
you should also be able to direct a driver somehow.. like not give him a destination but just say "driver turn right here, or go straight, or whatever.
also the outside messages like a normal car. you should be able to easily see what someone outside the taxi is doing. for instance if you wanna watch someone, or run from someone if they come along...
there was something else too... oh well I'll figure it out