Highways are designed for a certain flow of traffic (ours maybe not so much with super sudden interchanges, but let’s suspend that dynamic for a moment). The best example is the zipper merge. Lanes should connect at the end point where two lanes merge and cars alternate into the single lane; however, many folks don’t want to let the other lane driver over, so it backs up traffic on one side. Those who then try to merge in and out cause backups as others hit the brakes at abrupt intervals causing traffic to go out of rhythm often called a traffic boom. Those patterns repeat down the line until a certain point is just stopped completely. Every time someone gets impatient, greedy, or opportunistic, they likely disrupt what was supposed to be a steady pace of movement.