The Car$/$Truck$/$Bus$/$Motorcycle class allow us to make every car into an independent object. Each

vehicle should be able to move, erase, and display itself. To do this it needs access to the two

Place objects that represent its position. These cannot be member data of the vehicle object $-$ we

need to use only reference to the Place objects that are part of the Road. As the vehicle moves, it

unblocks the Place in the rear and blocks the Place ahead. Vehicle can also collect statistics about

itself $-$ the total time on the road, the waiting time, the distance traveled, etc. We see that a vehicle

designed this way has no knowledge of the world around it other than its position on the road, the

direction of travel, and whether the place ahead is free.