Update: David Pringle sez, "It was shown on BBC 2 television on 12th February 1971, as part of an arts programme called 'Review' (and then not re-shown until many years later, when indeed it did appear on one of the new BBC digital channels). But it's not an adaptation of the novel _Crash_, which was still more than two years away in February 1971. Rather, it's based on Ballard's book _The Atrocity Exhibition_ (1970), and particularly on the short piece called 'Crash!' therein."
Zack sez, "Fifteen years before David Cronenberg adapted J.G. Ballard's novel CRASH to the big screen — and two years before the novel even came out — Ballard himself starred in this short for BBC 4 directed by Harley Cokliss, co-starring Gabrielle Drake from Gerry Anderson's UFO (herself the sister of musician Nick Drake). It's a surreal, moody short about the fetishization of automobiles and auto accidents, though not as extreme as the novel and later film. There's a detailed description and analysis of the film and its making on this Ballard website."