[Arragonis]

Its a little bit like the pavement dance - you spot someone coming towards you on the pavement so you step to the left just as they step to their right leaving you still in each other's way. You smile, and step the other way just as they do so you still face each other.

In the case of merging you ease off a little to let someone in and they slow too, being polite. So you speed up. Just as they do to so you end up running alongside each other.

But you do get morons sometimes - one this morning was a classic. Traffic going 55-70 in two lanes so the giffer (very aged person) joining bumbles down the ramp at 40 - if that. The motorway was empty so people moved over but this guy made no attempt to merge. But when he was fully on the road he sped up to 80, so its not as if he didn't have the performance.