This is the electronic flywheel, for very smooth operation over the crossover and dirty track. Just be sure to follow all the rules for electrolytic, polarized capacitors, and wear safety goggles and face protection while testing your circuit. The capacitor might not be necessary if current was being picked up from the wheels under Santa's VW, however the idea does work well and could be used on most DC motors, I suspect, but don't use the flywheel circuit with HF AC. Perhaps a low tech solution, with no fancy circuitry, but it does prove that simple ideas do work.
Be careful when using capacitors! They must always receive the correct DC polarity and never be given voltage over their rating, or they can explode. I like to use a capacitor rated at approximately 3 times the voltage it may receive. Remember to protect your face, your eyes especially, when testing these circuits! If you are not familiar with using capacitors, get the "in person" advice of an expert.