I don't believe it was by design for effect either. I mean, since they
couldn't get away with a chauffeur-driven head of 5-0, I think the
crew did the best it could working around the fact that Jack Lord was
just a lousy driver. It explains the excessive use of stock footage
too.
I've got a brother like that. He's a dynamic individual, both educated
and worldly, but he's a born menace behind the wheel of a motor
vehicle -- a veritable accident waiting to happen.
My guess is Lord did very little of his own driving off camera, but I
figure riding a $200m fortune, not to mention transportation provided
by the studio, he never had to.