After selecting either the easy or hard course, Fire Truck began. Player one controlled the gas and the brake with the foot pedal, and also the front wheels of the truck. Player two controlled the back wheels. The fire truck raced down various twisting, turning streets, dodging various obstacles such as parked cars on the way. There was never a real ending to the game, the object was simply to drive as long as possible without crashing. Play time was extended if players did well, and when the game was over, their fire truck driving skills were qualified as "SORRY", "SO-SO", "GOOD", or "ACE".
The steering controls are where the co-op comes in. The fire truck behaved quite a bit like a tractor trailer. Player one could accelerate or brake as needed, and steered to control the driving rig up front. Player two had no control over speed at all, but could steer the trailer left and right as needed. Given the winding turns and all the obstacles in the way, plus the danger of oversteering, it took quite a bit of coordination to avoid a crash. If you did make a mistake and wreck, your failure was represented by a satisfying comic-book style "CRUNCH" on screen.
I've never had the chance to play Fire Truck, but I'd guess that playing it today, even with a co-op partner, would get stale rather quickly. However, you have to admire the creativity of the designers given the limitations of technology in 1978. Video games were brand new, and there were no established rules for what could be done. Basing an entire game off of driving a fire truck with a bell and horn is a bit silly, sure. But there are so many little quirks about Fire Truck that I can't help but find it interesting. Most of all, it's the cooperative gameplay that makes this game special, and fans of all the co-op games that followed should appreciate Fire Truck as a great early example of the gameplay we love.
Thanks to the Killer List of Videogames for the images!