Doubling up, at a price

Due to open later tonight, the long-awaited Mersey Gateway Bridge is a colossal new cable-stayed crossing between Runcorn and Widnes, set to relieve the Silver Jubilee Bridge and speed up journeys between Cheshire and Merseyside. But it comes at a cost.

Runcorn was very nearly a cul-de-sac on the northern edge of Cheshire until 1961. Sitting in the curve of the Mersey and the Manchester Ship Canal, it had water around its north and west sides, and was connected to the much more populous northern bank of the waterways by a railway bridge and a transporter bridge, shuttling a handful of vehicles backwards and forwards at low speed. The opening of the Runcorn Bridge (or, since 1977, the Silver Jubilee Bridge) changed all that.

The handsome pale green arch of the bridge has become a symbol for the local area and brought prosperity and opportunity that was unthinkable while the sizeable towns of the region were split apart by the river and canal. It was widened significantly in the 1970s to cope with the demands of Runcorn New Town and the growing number of commuters heading for Liverpool every day. Today, it's struggling to cope again.

The solution is to build a new bridge, and that's what has been happening just upstream for the last few years. The Mersey Gateway Bridge will provide a new dual carriageway across the river, soaring at high level over the water and suspended from three elegant towers. Three lanes of traffic will flow in each direction to relieve the rush hour crush. And to match its older sibling, its metalwork is painted the same shade of pale green.

A price to pay

Construction of the new bridge - and all its associated approach roads, changes to junction layouts in Runcorn and Widnes and demolition of some industrial units that stood in its way - is estimated to cost around £600m. That's big money for any project, but it's especially big money for a small borough in the north of England. The Mersey Gateway isn't a trunk road scheme, instead being promoted by Halton Borough Council.

No local authority has £600m to spend on a single infrastructure project, least of all one the size of Halton. The answer? A toll, to apply not just to the new crossing but also the existing Silver Jubilee Bridge when it reopens next year after extensive refurbishment.

The introduction of a toll poses three questions.

The first is whether it's right to impose a toll on an existing crossing that has, until now, been entirely free at the point of use. That's a moral judgement of course, one also being played out in the capital where Transport for London want to introduce a new toll at the Blackwall Tunnel to pay for the parallel Silvertown Tunnel proposal. In this case the decision is, very plainly, that a new crossing with a toll is better than no new crossing at all.

The second is how much existing traffic over the river will either divert across a parallel free crossing - perhaps going through Warrington town centre if it's local, or over the M6 Thelwall Viaduct if it's going further afield - and how many journeys simply won't be made at all. That's hard to predict and will be somewhat difficult to quantify even when the new bridge opens, but any displaced traffic will be sorely felt at Warrington's congested Bridge Foot junction and on a motorway network that's already running at its limit.

The third is the most bemusing question of all.

A borough of two halves

Halton - the borough choosing to build the bridge and to impose the toll on the existing crossing - is comprised of Runcorn, south of the Mersey, and Widnes to the north. It is literally split in two by the river and Ship Canal, its two halves linked only by a railway line and the Silver Jubilee Bridge.

What now forms the borough was originally part of Lancashire in the north and part of Cheshire in the south, and for as long as Runcorn was still a cul-de-sac the idea that it could be sensibly joined to Widnes would have been laughable. Incorporated for the first time in 1974, it is the Silver Jubilee Bridge, and only the bridge, that makes Halton viable as a single borough.

That is one reason why Halton wants a new bridge: it wants stronger links between its two halves. But the thing that keeps them apart is such a formidable obstacle that building those links comes at a steep price. So, to pay for it, crossing from one side of Halton to the other will no longer be free - for drivers of motor vehicles at least.

Will the new bridge bring Halton's two halves closer together, or will its toll form an obstacle of its own? Well, that is the central problem - the central contradiction, even - and everybody involved is so keen to downplay the impact of the new toll that the Mersey Gateway Bridge is subject to a series of concessions that go far beyond other tolls in the UK.

The conclusion is that effort is being made to make this as painless as possible because this is a toll that nobody seems to particularly want, but to which there is no workable alternative.

Indeed, if the project hadn't progressed through the planning process when it did - in the aftermath of the credit crunch, as a recession took hold, in times of spending cuts across the board - things might have been different. If the scheme had been progressed as a trunk road scheme - and it's hard to argue that it will only serve local traffic movements - then a flagship project like this under the control of Highways England with their much bigger budgets and spending power might have escaped tolls. If it happened to be in Scotland, Government policy there dictates that a toll would have been out of the question.

But the Mersey Gateway is the product of its times and its circumstances. At the very least, it may be tolled from the outset, but it will spend much less of its life subject to a toll than most comparable bridges. And for as long as tolls are levied, a good many more people will benefit from discounts and exemptions that will take the edge off the financial burden.

Full details of toll charges, discounts and exemptions are at the Merseyflow website.

A day in the sun

Whatever the controversy over its tolls, the new bridge stands to be one of the most impressive estuarial crossings in the UK - no mean feat in a country that's already home to the Humber Bridge, the various Forth bridges, the two Severn Bridges and many others. The Mersey is 1km (0.6mi) wide at the point the bridge crosses it, but the total length of the structure is 2.3km (1.4mi). Its three towers are, uniquely, all different heights: the north tower is 110m, the middle 80m and the south tower 125m.

Scotland has had all the headlines lately - the M90 Queensferry Crossing, another cable-stayed bridge with three towers, opened only last month. It has rather put the Mersey Gateway in the shade, being a much bigger bridge built at the same time and opening a few weeks earlier. But Queensferry is now more or less business as usual, so perhaps the opening of Halton's beautiful new bridge will earn it a day in the sun - one it richly deserves as a feat of engineering and as a striking new symbol for a previously anonymous and divided borough.

That is, if the sun comes out tomorrow.