If you're driving on a two-lane road, count the number of cars your car passes in an hour. A lot of people drive somewhat oddly on highways. Some will drive just below the speed limit for no good reason. Others will drive fast enough and then slow down without any reason. Others will drive way over the speed limit. A driver who doesn't keep up with the overall traffic's speed can actually create more danger by going too slowly. And, of course, driving too fast can get you into a big wreck!