In addition to cops, I'm also concerned with other drivers. Getting pulled over is a hassle regardless of the outcome and I don't really feel that it's my job to educate my local LE about my perfectly legal activities. So, I try to keep my vaping on the low while driving and especially while stopped at intersections to avoid having my tags called in by an overzealous concerned citizen. People generally fear what they don't understand so I just play it safe.