A couple of years ago Torbay council spent several months and I don't know how much money redesigning a traffic light interchange at a crossroads. From the usual system of each road getting alternate goes, we now have a junction where each of the four arms gets it's own green light whilst the other three sit at red.

I was sceptical whilst they were doing the work, but in practice it actually works and the queues at the lights are actually smaller and the traffic flows better.

Extract from that link (thank you Focussed):

He said: “Traffic modelling is done to national standards, but when you have real human beings using a road system you will find there are things you didn’t think would happen or people find other ways to use roads that you didn’t expect.”

He meant 'Traffic modelling is done in London by men in suits who commute by train, never drive anywhere except at weekends and have certainly never driven in Norwich'.

Doesn't this show that traffic modelling is either a) useless as a concept or b) performed by people who haven't got a clue what they're doing.

In the case of the North Shields Billy Mill works, its both a and b!