First thought to come to me (as a non-smoker) would be to ask before one lights up to allow me to pull over. Then (s)he can smoke as needed, just let me know a minute ahead of time. My car has never been smoked in, not even when both my wife & I were consuming a carton every 10 days or so (me a bit less). We didn't buy a car to stink it up, if that was desired, could had saved $23,500 (plus interest over the life of the loan) & kept what we had, or purchased an off-lease ride that may or may not had been smoked in.
Having stopped long ago (by chance 1600 days & 200 cartons of analogs), when I go into other's homes & they smoke, it doesn't bother me & won't cause me to relapse. No more than getting around others drinking, am a pain management patient & they have
a zero tolerance policy towards substances, even if legal. I would like to have a drink every now & then, yet it's not only the doctor's rules, it's outright dangerous to mix alcohol with highly potent medications to treat chronic pain, so I no longer drink.
So while I still have a small thirst for a drink (yet refrain), not so for an analog. We don't smoke in our apartment, was against the landlord's rules when we moved here (when I was still smoking), instead I went outdoors. Whether that be in the rain with an umbrella, sub freezing temps & windy, whatever.
I respected the property owners decision. However, once I started vaping, they allowed it once one walked in & thought strong coffee was brewing.
Bottom line being here may be your comfort level around smokers. I never had the issue, once I began vaping, was freed at last & literally gagged down my last few analogs. Too, if the smoking takes place in/on your property or theirs has a big impact, if yours, you call the shots, if theirs, you have no say. Based on what you're saying, may be good idea to get a couple of 'No Smoking' signs that attaches to the interior window with suction cups & avoid giving rides to those who smokes. On the flip side, if some of the same says the same about your vaping in their rides or home, you have little or no say in the matter.
It's your choice in your ride or home, if you feel that others smoking may cause you to have a relapse, even after they're gone, say no or offer to pull over for their break. Or because the smell will be stinky & leave residue behind, then I don't see any issue with not allowing it. You may lose a friend or two, or tick them off in the short term. On the other hand, if they're really your friends, they'll respect your decision because you stood up for your rights. Just be prepared for the same one(s) to not allow vaping in their rides/homes & respect their wishes as well, what may seem to be proper etiquette in one situation may be the opposite in another.
Cat