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Saturday 18 December 2010

Crikey Chaps, The Cable Car Doesn’t Add Up!

It might have seemed a jolly good idea at the time, but now the proposed cable car link across the Thames from somewhere near the O2 Arena to somewhere near the ExCel centre looks as if it might be troublesome for London’s occasional Mayor and regular collector of “chicken feed” from the Maily Telegraph, Alexander Boris de Pfeffel Johnson.

The project was intended to be self financing, via private capital. Sadly, this has not materialised, and Bozza has “directed” the London Development Agency (LDA) to chip in 1.2 million. And the cost has risen from 25 to 40 million. Moreover, the numbers being touted for the system’s people moving ability do not add up.

Articles both on the BBC website and on that of the Daily Mail put the capacity of the system as “up to 2,500 passengers an hour”. The Mail piece adds that there will be a headway of as little as 30 seconds. So let’s do the math. The Transport for London (TfL) page on the scheme shows a small cable car, like those that you can ride up to Montjuic Castle in Barcelona.

Typically, these hold four passengers, so one of these every 30 seconds gives a maximum hourly one way capacity of 480. Maybe larger cabins are being considered – so let’s double those numbers. It still only gives 960 – nowhere near 2,500. And cabins larger than that will need heavier cabling and more time to get folks on and off. As for being fully accessible – forget it.

Maybe, as the Mail article suggests, a cable car system with single large cabins is what is proposed. But those cabins only take around a hundred passengers as a crush load – so Bozza’s “serene and joyful journey” can be forgotten. Also, given the need to get everyone off and on, a headway of six minutes and an hourly one way capacity of 1,000 is as good as this concept will get.

So, in summary, the cost has been underestimated, the capacity has been oversold, and the USP of having the system open for the Olympics has been missed. Bozza would be well advised cancelling his direction to the LDA and giving up on this one.

[UPDATE: This article in the Evening Standard claims the cars will carry ten people. That's still only a one way hourly capacity of 1,200, and I'd be very interested to see how they propose to get all those bodies in and out of the cars and maintain a 30 second headway]

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