When walker got on the motorcycle to go after Guthrie he didn't strap on his helmet. When he caught up with Guthrie, he took off his helmet by unstrapping it.
They violated several Federal regulations regarding the transfer of the prisoner the prisoner and escort should've been boarded first. They also were supposed to be seated in the very last row of seats. Finally the restraints are to remain on at all times.
The station wagon that crashes into the sedan was a "beater"... an already banged-up derelict car.