I expect to get a lot of flak for this, but I've seen it too many times and want to know exactly what goes through their heads when they do it.

I drive a car. It's a small Ford Fiesta '14 plate, and I live in the UK, so take into account culture and so forth. Picture the setting. It's around rush hour time, with nice moving traffic in my lane (often going towards town centres to pick up my partner), and very slow stop-start traffic going the other way, to their homes. Many people have motorcycles to try to combat this, which is fine any dandy.

That is until the motorcycle weaves out between two cars and enters the opposing lane, often continuing to drive in that lane to avoid the long tailbacks. I've seen this happen at least 20 times over the past month (I only head out on Monday's and Friday's too), and I've seen many accidents caused by this manoeuvre.

I'm not saying that all motorcyclists do this, some are quite good and really courteous drivers. I just wish to understand why the ones who do cross into oncoming traffic do so, causing a massive hazard spike instantly, and often causing an accident with the motorcyclist or another vehicle alongside them due to swerving.

Please, those who have done so in the past, enlighten me.