Pussling equalities with Death Race 2000

Has anybody seen that there are "scary" things resembling between Pinchcliffe Grand Prix and Death Race 2000, during the race.
They both came out in 1975, with only a summer in between, but watch the race with the black car, which really is looking very alike.
And, the smokescreen they put out, and the oilspilling on the road during the tight race is done very much alike. It seems like the same idea.
How can that be?
Death Race 2000 had just been shown in the USA from may, before this film came out in august in Norway.
i know they worked on this film for at least 10 years.