SPB, why on earth would a traffic offence, alleged to have been committed by another individual, be included in a DBS (CRB) check? It makes no sense.

Do as you've been advised by me and a number of others right from the top of the thread - return the form with a letter explaining that the person and vehicle are unknown at the address, keep a copy of the form and your letter, and post it by Recorded Delivery - and stop worrying!