One of the fundamental rules of driving in Birmingham is that if the vehicle in front of you moves, then you should move too - even if you can't see that it's safe to do so, or there isn't physically room for more than one car, or whatever.
I was impressed to note that they're learning this from a young age, as I watched a young teenager on a BMX ride across the road (from the pavement into a car park on the opposite side) through a marginal gap in busy traffic. Wondering why the cars in front of me were taking so long to move off, I looked back up to note his mate following on a mountain bike, straight into the path of a lorry on the far side of the road. Luckily the lorry driver was paying attention and applied copious amounts of brakes. MTB kid proceeded to the car park entrance, where he stopped to show his appreciation in the form of an unintelligible shout and the universal sign for 'wanker'.
As I passed, I felt compelled to point out that that was a bit stupid. They looked at me, obviously confused, for a fraction of a second, looked at each other, and then reacted in the second most common way for teenage boys on seeing a recumbent bicycle.
*sigh*
Still, at least the four-wheelers were making an effort: I had one pull out nice and wide to overtake, until an unanticipated blind bend appeared out of nowhere, and they were forced to side-swipe me in case of oncoming traffic. Being used to this sort of thing, I was in an assertive primary, and had plenty of space to dodge into.