When you think of what the most annoying thing about driving is, what comes to mind? I, for one, cannot stand it when the person or persons I am driving with try to direct my driving. Not only is it insulting (because it makes me question my own driving skills and judgment), but it is dangerous because it is a major distraction.
The vast majority of licensed drivers who are the passengers in other people's vehicles always tend to think that their driving skills are better- or that the person who is driving needs an "extra set of eyes". However, this can prove to be extremely ineffective, often backfiring. For example, when I was driving with my boyfriend in the front passenger seat, I was stopped at the exit to my apartment complex and was preparing to make a left hand turn into traffic. However, before I could do this, I needed to check to make sure that the road was clear for me to go. I checked to my left, and when I went to check to my right, there was my boyfriend's head in my way. "Could you sit back? I can't see the traffic because your body is in my way" I said. As he started to sit back, he said: "Oh, I'm sorry- you're clear to go on this side though..."
Even if passengers have the greatest intentions of helping you out when you're driving, as a responsible driver, you can never make a driving judgment based on what another person says to you in the car. You still need to be vigilant and look for yourself. Some people might think that this is insulting, but it's not. This is why it is important to make sure that if you are the passenger in someone else's car, you need to keep your driving commentary to yourself. There are, of course, exceptions to this rule. For instance, if you are the passenger in someone elses car and you see a hidden danger that the driver is unaware of such as a pedestrian running across the street at the last minute or another car about to turn into your vehicle, then you should feel free to alert the driver quickly.
There are also times when backseat drivers can contribute to the driver of a vehicle getting into an accident or becoming incredibly distracted. When you are driving, you should be calm but alert. However, if you have a passenger who is relentless when it comes to his or her commentary about how awful other people are driving, it can actually turn a calm driver into a more aggressive or agitated driver, which may or may not contribute to that person getting into an accident. Road rage is not a good thing to have while driving because those who drive while displaying road rage are more of a danger to other drivers who may not have time to react accordingly.
The bottom line is, when you are with someone else who is driving, be the sort of passenger that you would expect them to be if you were in the driver's seat.