To me it just sounds like one extra thing to carry that you really don't need. I've found a squirt of the water bottle to be just as effective on a dog pretty much all of the time. Although I haven't been chased for a while. As far as a passing motorist goes, I doubt a spray of tear gas has sufficient momentum to halt an errant car. The idea of using tear gas on a motorist is dependent upon them getting out of the car in the first place. I honestly can't remember the last time a motorist having a go at me actually did that.