A GPS unit can be used by someone who is walking, running or riding a bike, but most people use it in the car. It has completely replaced the paper map, and many modern drivers can't believe they ever got around without it. Thinking of reading a map or printing out step-by-step directions sounds archaic.
Still, despite the fact that the GPS is so common and focused largely on automobiles, it is still a significant distraction for many drivers. If not used properly, it can cause accidents.
Think about it like this: Many experts claim that looking away from the traffic around you for two seconds increases the risk by an accident by 100%; that is to say, the risk doubles in that short time. Any distraction that makes you look away from the road can lead to a crash.
With that in mind, consider that the average amount of time needed to program a destination into your GPS unit is 40 seconds. After that, your brain can't fully refocus on driving for 13 seconds. That's a total of 53 seconds, or nearly an entire minute, without your full focus on driving. If two seconds of distraction can double your accident odds, what can a whole minute do?
Programming the GPS before you start driving is very important. Unfortunately, even if you do so, not all other drivers are going to follow suit. All it takes is one distracted driver to put you in the hospital. Be sure you understand all of your legal rights to financial compensation after a significant crash.