I vape openly all the time--on foot, in my car, whatever.
I live in the People's Republic of Maryland, where police abuse of civil rights is so bad that the City of Baltimore actually has a budget line item every year for Federal Civil Rights lawsuit settlement payouts. Violations of procedure, and of civil rights isn't a "problem" in the urban counties of MD--it's a calculated, intentional, fundamental part of how the system works, and they actually make financial provisions for when they get caught (rather than just telling the cops here to NOT be thugs...)
I've never been harassed by an LEO. Maybe I've been lucky. Then again, maybe it's because I'm over 40 and drive a purple HRR with pro-gun stickers on the back--they probably figure I know my rights and have a good lawyer on speed-dial, and so don't treat me like an "easy mark". I notice most of the people being harassed for vaping while driving are 20-something men and young women--which are the preferred target group for predatory thuggish cops...
If you are not driving erratically, or have defective equipment, the mere presence of an e-cig should not constitute "probably cause" under Terry vs. Ohio. Without clear evidence of a crime, there is no legal, legitimate reason to pull you over.
PVs are common enough these days that their mere presence does NOT even meet the requirements for "reasonable suspicion" let alone "probable cause".
I would send the Chief of police in your jurisdiction a PR package from CASAA, via certified mail, with a letter from a lawyer letting them know you are putting them on notice to update their training and procedures, and future harassment will be considered a knowing violation of your civil rights on their part, and will result in legal action under 42 USC § 1983, 1985, and 1986...
42 USC § 1983 - Civil action for deprivation of rights | Title 42 - The Public Health and Welfare | U.S. Code | LII / Legal Information Institute
42 USC § 1985 - Conspiracy to interfere with civil rights | Title 42 - The Public Health and Welfare | U.S. Code | LII / Legal Information Institute
42 USC § 1986 - Action for neglect to prevent | Title 42 - The Public Health and Welfare | U.S. Code | LII / Legal Information Institute
We need to stop playing nicey-nice with these thuggish LEOs. We need to stop making excuses for their illegal behavior. We need to stop trading our dignity, freedom and the Rule of Law for the false promise of "protection" and "safety". Because when we trade our freedom for safety, we end up getting neither.
Pay a lawyer $50 to draft a letter for you and send it to them with CASAA packet certified mail. If your local police want to act like thugs and bullies, you need to let them know that YOU are not the person they want to pick on in the future. And your action may actually save someone's life--the next person they pull over may be a young woman, or someone they say "looked like they had a gun" when they are holding a box mod, and the end result might be a LOT worse than being late for work...