There would be two different trains with very different specs, one might be great at erm wind resistance or something while the other may not be but would make up with something else. Then you have slowing down for tight corners, so it would depend on how good the driver is to help get round those smoothly and also get the train back up to speed. You could have obstacles like having a leaf on the track so your train could be "souped up" to deal with those but may have to forfeit some kind of speed booster to have that on your train.
EDIT: Just realised this could be co-op, one driver, the other shaking the wiimote like fuck to get fuel into the furnace.