People who like to drive rarely enjoy being driven - and are often tempted to second-guess the driving of others when not behind the wheel themselves. Usually, it's not a good idea. Here's a Backseat Driver's Companion - a short list of Do's and Don'ts to follow when someone else is behind the wheel:
Hold your tongue
You may not like the way someone else drives; maybe they don't notice the light's turned green as fast you might; maybe they're more hesitant than you might be pulling into traffic or merging. But unless there's an immediate danger you're pretty sure the driver hasn't noticed (a kid on a bike about to run across the road, for instance) proper etiquette is to remain silent, even if it makes you stew inside. When you're back in your own car and behind the wheel again, you can drive how you like. Hectoring those who don't drive as you might isn't going to change their ways; it's just going to create stress and may even make them drive unsafely.
Don't second-guess
Maybe you do "know a better way" to get across town - or "just know" the car will fit in that parking spot up ahead that looks pretty tight. Ultimately, it's not your call. It's fine to give advice if it's asked for. Just don't hector and nag imperiously. You may in fact be a much better driver, know the quickest way to get across town and could easily parallel park the car in that tight space up ahead. But since you're not behind the wheel, it really doesn't matter. Grin and bear it. Everyone will be the happier for it.
Abide by "House Rules"
That means (within reason) doing what the driver asks. It's his car, he gets to lay down the law. If the driver asks you to wear your seatbelt, for example, it's right and proper to do so without complaining - even if you prefer not to wear a seatbelt in your own vehicle. Same goes for smoking, eating and drinking. If it's not your car and you're not driving, deference is the order of the day.
Don't create distractions
It's unsafe to yak on a cell phone while driving because your attention's not fully focused on the task of driving the car. For the same reason, passengers who distract the driver can be just as dangerous - or more so, since the driver has little or no control over how passengers behave. You can turn off a cell phone; it's virtually impossible to "turn off" a passenger creating a distraction in the back seat. This is a problem for teenagers and young drivers especially. Put a bunch of kids in the backseat - and a kid up front in the driver's seat - and the odds of a distraction-induced accident go up several notches. If animals are on board, keep them under control. A dog running amok inside a car is another great way to set up a tragic accident-via-distraction.
Offer to share the driving
On longer trips, it's courteous to make it known you're willing to help with the driving - if the driver wants a break. This should be done in a non-confrontation way; don't say "I'll take over now." Say something along the lines of "Whenever you feel like taking a break, let me know. I'd be happy to drive some of the way." So long as you're not offering a critique of the other person's driving - and implying you could do a better job - the offer will usually be taken in the right spirit. And there won't be a potentially dangerous test of wills: You waiting for the driver to get tired and slip up (so you can point out the slip-up); the driver adamantly refusing to admit he's getting tired and letting you spell him - just to prove he's a better driver than you think he is.
