Attention very angry man in the van behind me!

There is a really good reason why I’m driving fairly slowly and leaving a large gap in front of me on the Warringah Freeway. Believe it or not, I’m doing you a favour – you and everyone in the lane behind.

When driving in heavy traffic, patterns of stop-start movement will emerge; sometimes because of a near miss, sometimes because of an accident, or sometimes because of absolutely nothing at all. But once that pattern has emerged, shock waves propagate slowly backward though the traffic, causing people to have to hop on and off the accelerator and brake. It’s no fun to drive in (particularly when, like me, you drive a manual).

Here’s a video both explaining and illustrating the phenomenon:

One Seattle driver discovered that there was a solution for his frustration of getting on and off the gas & brakes. By driving at the average speed of traffic, instead of rushing straight toward the stopped bumper ahead, he caused the flow pattern of his entire lane for miles behind to smooth out. In traffic flow terminology, he figured out the secret to transform a “wide moving jam” into “sychronised flow”. Amazingly, this behaviour can actually improve the overall flow rate of the traffic: more cars can travel along a given road in synchronised flow than in the presence of a jam.

Anyway, angry flashy-light van driver, I thought I’d do you the courtesy of explaining my behaviour. I hope you understand.