£131m per mile road

[Gob]

Two short lengths of road are about to open at a combined cost of £1bn. They represent a last hurrah for expensive road projects in an era of cost-cutting.

At a time of austerity, the idea of spending more than half a billion pounds on a five-mile stretch of road might seem strange to some. But the M74 extension is about to open in Glasgow at a cost of £657m, which works out at £131m per mile or £75,000 a yard (£80,000 a metre).



The elevated six-lane highway pushes through the heart of Glasgow like some Corbusian vision of the machine city. For a few weeks it will be the second most expensive road per mile in the UK - after Limehouse Link, in London's Docklands.

But in July its silver-medal status will be trumped by the even more costly A3 tunnel at Hindhead in Surrey. A four-mile section of dual carriageway is being added, but the vast bulk of the £371m cost is concentrated on the 1.2 mile (1.9km) tunnel. It is the longest road, under land rather than a river, in the UK, costing around £300m, equivalent to £142,000 per yard (£155,000 per metre).

It's no surprise these projects are expensive, says Geoff French, vice president of the Institution of Civil Engineers.

"There's a huge cost penalty when you put a road up in the sky or down in the ground," he says.

A mile of new motorway costs on average £30m, according to the Highways Agency. As a rule of thumb, an elevated road costs 10 times more than one on the flat, says French.

The M74 passes over roads, railways and the River Clyde and its longest bridge, the 2,500ft (750m) Port Eglinton Viaduct, spans the West Coast Mainline railway.

"The incredible thing is how close to the centre of Glasgow it is," says Sir Peter Hall, Bartlett professor of planning at University College London. "Some of the exits will be five minutes to the city centre."

That affects not just the engineering but buying up land. The compulsory purchasing of property in the M74's path cost £200m, according to Transport Scotland. That is on top of the expense of running planning consultation and public enquiries.

An underground road costs even more - roughly twice that of an elevated one, French says. Such arithmetic saw Boston spend around $20bn (£12.5bn) on its Big Dig that rerouted the city's main highway into a 3.5 mile (5.6km) tunnel.

Completed in 2007, it was controversial for being the most expensive highway in US history. Perhaps with that in mind, New Jersey Governor Chris Christie last year cancelled an $8.7bn (£5.5bn) rail tunnel under the Hudson river at Newark.

But sometimes there is no alternative to going underground. Currently, the A3 dual carriageway from London to Portsmouth is forced to narrow to a single lane in each direction at the Devil's Punch Bowl beauty spot, creating a notorious traffic blackspot.

The tunnel allows the road to expand to four lanes by digging up to 195ft (60m) under Hindhead Commons. "Building a dual carriageway on the surface would have caused great damage," says Rob Fairbanks, director of the Area of Outstanding Natural Beauty, which contains the Devil's Punch Bowl.

The Hindhead scheme is made up of two separate tunnels, one for each carriageway, which are linked every 330 ft (100m). More than 4,000 people worked on the project and 26 million cubic feet (737,000 cubic metres) of earth have had to be excavated during the tunnel's construction. It is equipped with lights twice as bright as the floodlights at Old Trafford.

The most expensive road per mile is the Limehouse Link. The 1.1 mile (1.8 km) tunnel in London's Docklands opened in 1993 at a cost £293m. Adjusted for one measure of inflation that would be £445m or £230,000 per yard (£250,000 per metre). It was designed and built in seven years and at the time was the second biggest engineering project in Europe after the Channel Tunnel.




http://www.bbc.co.uk/news/magazine-13924687

[Guinevere]

Still a bargain compared to Boston's Big Dig, a $22b project -- the most expensive in the US. It includes elevated highway, tunnels, and bridges, and comes out at well over a billion per mile of road.

And yes, the traffic congestion still sucks.

[Jarlaxle]

You forgot the fact that the Big Dig is already falling apart! A ceiling panel fell and killed someone. Also, there have been light fistures and insulation falling onto the road...as well as serious water leakage (sometimes resulting in lane closures due to ice buildup!).