Have seen similar racing here in the UK in the dim and distant past. I think that is was billed as "Grass Track Racing" . One event near Clyst St Mary, just outside of Exeter raced just 4 cars at a time, with a pair of cars starting, then after a short pause a second pair of cars being allowed to give chase, A car that stuck in my mind from that event was a Hillman Imp bodied creation that had a Mini subframe and motor at the front, while retaining the Imp motor at the rear. When it went it went well, but suffered a number of mechanical problems during the day. The other event I remember was held at Gosford near Ottery St Mary, East Devon. and was more in the style of the event shown in the video.. Both of these events would have been roundabout 1974.