I can remember some betting at a track, many years ago. You had to guess the finishing order, by helmet colour, and the decimal point of the race time.
Always seemed like, although speedway knowledge would help for the first part, the second was just random luck.
Was not a success so the bookies gave it up.
I personally thought at the time, that if races got delayed, so bets could be put on, that I would give up following speedway.