Any vehicle can be a grid car with the proper equipment. Grid cars are a staple of life in The Inner Universe and can also be found on most developed worlds of The Frontier providing safe rapid travel through most cities. These vehicles vary in passenger capacity and some times propulsion (Inner Universe vehicles are almost always Hover Tech aside from collectors models, in the Frontier they are normally what ever you can get moving) from world to world but all follow the same concept.
Vehicle's are fitted with a transponder and auto navigation system that ties to the city's traffic system. This allows people to get around town by simply inputing a destination and relaxing. Authorities can redirect vehicles with ease in event of emergency and outright override them in extreme cases. It is crime to operate a vehicle without a grid system in The Inner Universe(manual controls are not even installed in most Inner Universe cars) but on The Frontier you just lose the benefits if they are even there to start with.