Britain From Above 1. 24 Hour Britain (24 of 28)

Britain From Above

Eddie, if motorways are like human rivers of some kind, the great thing about this is we can look down on the river.
What kind of things are you looking for here?
What we have here is the merge of the M5 and the M6 junction in Birmingham, and we have M5 traffic coming in from over there, from the south, and we have the M6 traffic coming in from the east.
And here there's just too much traffic being pumped into the pipe, and we see this kind of traffic pattern here every Friday.
Right, too many cars and lorries, not enough Tarmac.
But what about those strange jams where there's no accident, no police, there's no roadworks, it's a mystery?
EDDIE: There doesn't necessarily have to be a cause such as an accident.

The problem is, because drivers' behaviour is not perfect, people get too close to the vehicle in front, then they have to correct, they touch the brakes, the guy behind touches the brakes, slows down a bit more, and if you go 100 vehicles back up the column of traffic, somebody actually comes to a stop.
So all it takes is one person braking just a little too hard, and the next thing you know, a mile or two behind them, the whole motorway has ground to a halt.
But that's not the end of it.
Using computer modelling, Eddie and his fellow motorway gurus can allow us to see what happens once the motorway lanes have become clogged with stationary traffic.
Even though the stopped cars quickly start moving again, the jam itself doesn't vanish.