This isn't a normal slot racing set. I am pretty sure it has a long spring in each slot which is driven by a motor. It uses Matchbox diecast cars and there should be clips in the set with a peg on them which sticks down at 90 degrees to the underside of the car. The clip attaches to the chassis of the diecast car and the peg clips into the spring in the slot. When you operate the controller the spring revolves in the slot and drags the diecast car along. The controller alters the speed of the spring. The more you press the faster the spring turns moving the car faster. You can use more than one car on each lane but too cars many will overload the motor turning the spring.
It was made in 1967 and is probably of more interest to a Matchbox collector than it is to most slot racers. I don't think any cars were included in the set.
If you check the sold listings on Ebay the prices range from $50 to $150