If you employ a chauffeur, then you’ve fairly bought the privilege to criticize his performance as harshly as you please. But, the rest of us ride gratis, so we bite our tongues. Occasionally, we witness our friends, family members, co-workers, and classmates behaving irresponsibly behind the wheel. We feel with them; no one appreciates a back-seat driver. They aren’t our chauffeurs, and we can’t very well treat them like servants, can we? To criticize an equal’s every little fault would be—indecent.

And, anyway, their errors are mostly forgivable. They pass on the right, they merge across a solid white line, they devote both hands to fiddling with their cellphones while “steering” with their knees…No, wait! Stop! That’s super-dangerous! Even riding with friends, family, members, co-workers, and classmates, situations like the latter do arise that positively demand criticism. Where is the line? It’s probably closer to everyday life than most would suppose.

Plenty of facts and statistics support passengers intervening to dissuade drivers from behaving irresponsibly behind the wheel. For example, “distracted driving” caused 3,459 deaths in 2015. Of all those who died in automobile crashes that same year, 48% were not wearing their seat belts. The truth is plain enough: If we would speak up, we’d have no lack of things to say.

None of this evidence is really relevant to the question, though, is it? We all know how dangerous distracted driving is. We all know we should wear our seat belts. We all know we should obey the rules of the road. Like smoking in the presence of a baby, the question is really one of the limits of propriety: How serious an offense should one permit before protesting? How much smoke is it worth exposing a baby to before enough is enough, and any decent person would break that silence? The National Highway Traffic Safety Administration (NHTSA) offers some good guidelines for passengers in a variety of situations and—what’s most helpful—relationships to the driver. This graphic also suggests a few polite ways passengers can encourage safer driving, as does this one aimed specifically at teenagers.

The bottom line is this, though: the limits of propriety exist not to hinder and confuse but to assist living-together. If you know something makes living-together more difficult, like behaving irresponsibly behind the wheel, is it not right and proper to speak up? Even as passengers, we have that power—and no rational system of ethics denies the exercise of power to those who would use it justly. On the contrary, all of the best ones insist on it.

NC Vision Zero aims to empower North Carolina’s passengers. You can assist in their mission—and win an enviable prize to boot—by participating in the Empowered Passenger Video Contest. For more information, look up ncvisionzero.org/empoweredpassenger.