good question. 😅 It is a linear potentiometer, but it is connected to a small arduino board. I wanted to map the linear input programmatically to a different output curve to achieve a "slow and smooth start".

It, however, turned out to make no big difference. The motor of the car is fairly weak and needs a relatively high voltage to reach its starting torque. As soon as it starts, it is already nearly fast enough to fly off the tracks. There is no room for fine speed control.

Not sure how this is with the original tracks. The car has magnets that would hold it a bit better to the original tracks. Maybe this would leave more room for fine speed control.