The BBC reports that the estimated construction costs of the Thames cable car have been revised. Again. Upwards. The estimate has gone from £25M initially to £60M, and it will be paid for partially out of the rail budget.
It occurred to me that the point of this cable car is rather unclear. If it's being paid for out of the rail budget, then it must be a transport project, and on that basis it must stand comparison with other transport projects costing £60M. On the other hand, if it's simply a tourist attraction, then why is it being paid for out of our already stretched transport budgets?
To pass muster as a transport project, it has to deliver as many people as possible as fast as possible where there is demand for travel. The fares need to be reasonable, and you need connectivity.
I'm not an expert on cable cars, but a bit of googling indicates it's not the fastest mode of transport (gasp!). The world's longest cable car system, in Vietnam, achieves an average speed of around 20km/h over about 5km. The Thames cable car will run from North Greenwich to Royal Victoria Dock. That'll be handy if you live in North Greenwich and work near the Royal Victoria Dock, or vice versa, but it seems a safe bet that there's not a huge market for that particular journey. Will it be any use for other journeys? It seems unlikely. For any other journey you will end up changing at one or both ends, and the Jubilee Line stops at North Greenwich and crosses the river nearby giving a faster, better-connected option. I suspect there are very few journeys that will be faster given that the cable car run is a slow 1 km plus a walk at either end. On the other hand, the view will be better. That brings us onto the tourist attraction aspect. For tourism, you can set the fares rather higher, but for regular transport you can't charge much more than the cost of a bus fare for such a short journey, given the presence of alternatives. If the cable car is going to attract more tourists than people using it as transportation, which I expect it will, should it be subsidized or paid for out of transport budgets?