Can you imagine if you were driving a car at 70 mph in traffic and surrounded by heavily loaded trucks when the bear spray lets go? The pucker factor would tend to rise a bit.

Such sprays should be transported with the safety taped or wired down, double-bagged in plastic garbage bags with the air pressed out, perhaps with something absorbent, like towels, in each bag. Cans of spray can also let go if they overheat so keep them as cool as possible.

Many years ago SOP with some military units that carried spray was to keep it in an ammo can bolted to the rear bumper. That way any leaks were down-wind while driving.