this is really puzzling. In English, you can be on a train, on a car...meaning that in fact you are in the respective means of transportation. (that's what I was taught in school) And the -ra case, according to the tips, shows motion to/onto something. So there is a confusion of movement implied by -ra vs the statioanary meaning of waiting. But let's not be picky, and accept that I am waiting on a red car. Yet, there is the suggested translation that I am waiting for a red car. I am not sure how the authors got to this suggested answer, since there is no accusative -t mark for the car. The suggested translation must be a mistake.