 These vehicles are released one at a time at regular intervals, and tests to see if the bridge components stand up to repeated stress or if the crossing of paths causes any collisions.There is no building limit for a level, but each bridge component placed in a solution has a monetary value, and the player is challenged separately to keep the total monetary value as low as possible.The player clears a puzzle by getting one vehicle across, but is rated higher by getting all of the vehicles in a convoy through the course without harm.