How is this possible?

Three cars all driving side-by-side down the highway all doing 60mph, which is technically the speed limit, but how did they end up next to each other? If they're all doing the same speed shouldn't they be spread out along the road? Do they slow down and wait for one another? And the most important question is... Why am I always the behind them? I hope my theory that this is the sheriff''s  new way to control traffic is wrong, wrong, wrong.