The show was intended as a spin-off from another Quinn Martin production, Cannon (1971). Ultimately, they produced three crossover episodes (guest-starring Cannon's William Conrad), including the Barnaby Jones pilot, "Requiem for a Son."
Occasionally a car may run off a cliff or crash and then explode. Gasoline is volatile but not explosive, so there is no reason for the cars to explode.
During original broadcast run, the opening credits would follow the setup scene. Therefore the first victim was not listed among the guest stars since their character is already dead. Only in Barnaby Jones: Deadline for Murder (1980) was initial victim, Alex Henteloff, included in the opening credits.