A while back, on Bishops Bridge Road in Paddington, there was a massive traffic jam.

There wasn’t usually a serious traffic jam there but this was solid.

The problem was a bendy-bus trying to turn right at the traffic lights at Gloucester Terrace.

There was enough room for the front part to go but not the rear part, so the front part was stuck across two lanes blocking north and west traffic, the rear part was stuck across the other two lanes blocking south and east traffic, no one could move and the bus driver couldn’t reverse.

And this was the vehicle that was planned to replace all London double-decker buses.

At least that was how the planners saw it.

The planners hailed it as the future, the same buses used in beautiful cities like Seattle, San Francisco, Toronto, and Sydney; London would be like them, all bendy buses and cyclists.

The only problem was that London was nothing like those other cities, London was eight million people, one of the biggest, oldest, busiest cities in  the world.

Changing buses wouldn’t change the juggernauts, the trucks, the vans, the taxis, the cars, the motorbikes, the coaches, the pedestrians, the rush hour.

But that’s the thing about planners, they confuse fashion with thinking.

For them, London had old-fashioned double-decker buses with conductors, all of which made them the dinosaurs of transport.

So they bought a fleet of bendy buses, each bus costing £360,000 (£700,000 today).

The entire fleet of 130 buses cost £47 million (£90 million today).

But they ignored simple old-fashioned common sense.

A double-decker bus is 30 feet long (9 metres), a bendy-bus is double that, 60 feet (18 metres).

So a driver is doing the equivalent of driving a bus while towing another bus behind.

This may work in modern cities with straight, wide roads and gentle curves, but London has grown from a medieval city, so a lot of the roads are crooked and narrow.

And in heavy traffic, a driver changing lanes often had the front part of the bendy-bus in one lane and the rear part in another lane.

Traffic accidents with buses increased 75%, the length of the buses meant they were blocking more road users, and the drivers couldn’t watch both parts at the same time.

And because the bendy buses had no conductors, fare evasion increased to £7.1 million (£13 million today), people just entered the rear part without paying.

They were particularly dangerous for cyclists, who would overtake before realising how long these buses were, and the drivers couldn’t see them.

The bendy-buses were such a disaster London went back to double-decker buses in 2009.

Eighty of the bendy buses were sold to Malta, but they were a disaster there and were sold for scrap in 2011.

The crazy rush to follow fashion at all costs had proved an expensive mistake.

But that’s the way it is when theory overrides practice, when fashion overrides common sense, when marketing-thinking overrides advertising-thinking.

Just because we want things to be certain way doesn’t mean it will work.

Just because we fall in love with our own desire for fashion and change.

Just because it makes sense to us doesn’t mean we can ignore external reality.

Our love of the latest thing shouldn’t ignore common-sense.

As Paul Feldwick said about clients believing in the infallibility of research:

“We’d all like to know the winner of the 3.30 at Kempton Park tomorrow, but wanting it doesn’t mean it’s realistic.”