Imagine you’re driving in a 40MPH zone, innocently enough, passing the slower vehicles at 45MPH. Why their speeds are varying from 30 to 40 you don’t quite understand, but you pass them anyway.

You finally work your way up to the front of a pack of vehicles and are almost free and clear, when your progress becomes blocked. Two people are driving parallel to each other at 37MPH. Every few seconds, one of them speeds up to 40; only to realize they’re pulling ahead and let off the gas to fall back.

My theory is that they notice they’re pulling ahead of the other vehicle, and thus assume they must be speeding; which results in a sudden decelleration. Obviously one of two things is happening:
1. The driver believes the spedometer in the other car is more accurate than their own.
2. The driver wishes to ensure neither vehicle passes the other; thus creating a logjam behind them. It has been my observation that many traffic jams begin this way.

These theories indicate the drivers are unaware of the dampening effect they are having on the flow of traffic. In fact, having been a passenger in such a vehicle, they don’t even seem concious of what’s going on. They’re happy being out in front of the pack, entirely clueless as to why there are cars behind them but not in front.

Are you a parallel driver? It’s a rhetorical question; you probably aren’t even aware you’re doing it. Pay attention.