h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I don't enjoy traffic jams but I can (almost) accept those for which there is an obvious reason. Faulty traffic lights, for example, or an accident, or loads of traffic coming on to the motorway at a junction in the rush hour. What really causes me mental problems are traffic jams for which there is no apparent cause. A few weeks ago I was driving along the M25 (anti-clockwise from the Dartford Tunnel) when all the traffic stopped. This was at around 5p.m. It continued to be virtually stationary for about an hour. Traffic on the other carriageway was moving freely. Suddenly, at about 6p.m., the traffic started to move freely again. There was no evidence of an accident, and the hold-up didn't coincide with a junction. It was as if some one had said 'Nobody gets past this point until 6p.m.' Strangely, just as the traffic on my carriageway started to move freely, traffic on the other carriageway backed up, again with no obvious cause!

I would be grateful if some one who uses the M25 on a regular basis could tell me if this is a regular occurrence.

P.S. I had driven down the M25 earlier that day and had no problems. People tell me that the M25 is a 6 lane car park. Maybe I was lucky.

Well, the M25 (and M1) has its own natural, and unnatural laws. Last time I was driving back from Hull, on the M1 the traffic backed up for 2 miles - all due to an accident on the OPPOSITE carriageway. Rubbernecking people stopped to look on the outside lane. Then, on the M25, the outside lane just stopped because there were so many cars in it. All the other lanes continued fine. People just don't know how to use motorways, as I point out in my article on the M4 if you're interested.

Your comment on rubber-necking applies to every motorway I have ever travelled on. And I've travelled on a lot! My husband's suggested explanation was wildlife on the motorway. Apparently swans frequently mistake motorways for rivers, particularly if it has been raining (which it had been that day), and land on the motorway. He reckons this might have caused a hold-up similar to the one I experienced.

I believe that these Mystery Jams are actually caused by bad pop music. I live in Houston, one of the most notorious cities for traffic jams in the world. After spending many years (cummulative time) in traffic I have developed the following theory to explain many of the snarl-ups I've been in. Traffic is flowing quite nicely if a bit thick when suddenly the radio station some young fellow is listening to starts to play a song he has heard too many times and wasn't that fond of in the first place, say something by Oasis. So, he reaches over to change the station and for a moment takes his eyes off the road. He finds something better on the radio, say Primus, and looks up. He suddenly realizes he is too close to the car ahead and taps on the brakes. This creates what is known as a Standing Wave. The drivers behind him see a brake light so they tap on their brakes. The wave of brake lights flows counter to traffic flow until it reaches an overpass. Since the drivers behind the overpass cannot see the brakelights until they reach the top of the overpass it has a chance of stopping there. But as each and every driver rounds the top of the overpass and sees the brakelights ahead of them, they will instinctively slow down. NOONE caught in this standing wave has ANY idea what caused it in the first place, but they were following to closely to the car ahead of them, so they have to brake. Two hours later I come down the road and now I'm stuck driving my car at 10 mph in a 75 mph zone because the Gallagher brothers just had to release another "hit".

The Standing Wave theory is absolutley correct. However, there needs a modification in that when drivers in lane 1 realise that lane 2 is moving faster, they change lanes, causing a snarl up in lane 2. People behind them see this and change lanes too (the copycats). This frees up lane 1 until people from lane 2 realise that lane 1 is moving faster and begin to change. It is entirely possible to halve journey times on the M25 by learning and reading the pattern of lane changes and adapting accordingly. Thought obviously, if the buddists are right, the hatred from the other drivers will probabaly ensure you return as a dung beetle in the next life.

I can see this 'standing and transverse wave theory of traffic jams' could be very interesting. Possibly. There's definately a hefty research grant in there somewhere. We need someone to explain why it takes nearly an hour for me to travel just 4 miles into Manchester every day. I too blame pop music. Particularly B*witched. Bunch of tarts that they are.

If it's four miles why not do it on a bike? Twenty minutes/half an hour max, no sweat, whatever the traffic does. ~Recumbentman (see A891830)