In City Tour, you and the other players want to pick up passengers in your bus and deliver them to the right stops. How many passengers? That depends on how difficult you want the game to be!
Set up the frame of the playing area, and place the bus in the starting area. On a turn, someone draws two tiles, then places one tile into the frame, discarding the other one. If you add to the road in front of the bus, the bus moves as far as it can, picking up any passengers waiting on the road and dropping them at the appropriately colored bus stop. (Blue passengers only go to blue bus stops, of course.)
The bus has only six seats, so you need to manage travel carefully so that you don't strand too many people and have no chance of meeting your goal.