I believe it's based on what the brain considers valuable information (or necessary to determine the situation). When you drive a longer distance the first time

I believe it's based on what the brain considers valuable information (or necessary to determine the situation). When you drive a longer distance the first time it seems like a year. After driving the same distance plenty of times the brain filters out the information as it's considered "safe" or of no value. The opposite happens if you are in an accident, the brain needs all the information it can get, time seem to slow down as a lot of information is taken in. Just my theory anyways; condensed: time perception is relative to information stream the brain takes in.