The trouble with the Thames

The Silvertown Tunnel took another step closer to being built a couple of months ago. But it faces stiff opposition, and no proposal for a new river crossing in East London has succeeded since the first Dartford Tunnel opened in 1959.

Transport for London now have Development Consent to build the Silvertown Tunnel, a new road link across the Thames between North Greenwich and Silvertown, close to the existing Blackwall Tunnel. It's taken a very long time to reach a point where construction now looks likely - and on the way, two other planned river crossings have been abandoned. Why are TfL still so keen to build a new road tunnel at all?

Let's take a step back.

The story so far

East of Tower Bridge, there aren't many links between the roads north and south of the Thames. There's the A101 Rotherhithe Tunnel, opened in 1908 and subject to strict speed, size and height restrictions; there's the A102 Blackwall Tunnel, with a Victorian northbound bore and a 1960s southbound bore, which means some heavy vehicles can only use it southbound; and there's Dartford, with its twin tunnels and cable-stayed bridge, which is subject to a toll. Oh yes, and the Woolwich Free Ferry, which is really only suitable if you have time on your hands.

Nobody is really happy with this situation.

Blackwall suffers chronic congestion in both directions, with morning rush hour queues often persisting until the end of the evening rush hour, and the slightest hold-up (such as an overheight lorry being diverted off the approach road) having almost unbelievably severe consequences. The traffic problem at Blackwall is hard to overstate; TfL's own figures show that, on average, it operates without some sort of incident on only one day in every two weeks, but even without incidents, "normal" operation means queueing for up to half an hour to get through.

Rotherhithe permits only light traffic and has no approach roads to speak of, so it is not much use for many journeys simply because it's hard to actually get to it, especially on the south side.

Dartford is well outside London - eleven miles east of Blackwall, the previous crossing, and is tolled. It's also the river crossing that carries M25 traffic over the Thames, so it has its own problems dealing with traffic that has no business in London. Nonetheless, plenty of journeys to and from places in outer East London go via Dartford simply because the alternatives are far away and far too slow.

Since the 1960s, there have been plans to increase the number and capacity of river crossings to sort this problem out:

• A third bore at Blackwall to carry six lanes over the river instead of four, planned since the late 1960s. By the 1980s a bridge was being proposed to double capacity, with a total of eight lanes. Neither were built.
• A new tunnel at Gallions Reach, near Thamesmead, was proposed in the late 1960s as an eight-lane motorway (part of Ringway 2). The plan returned in the 1980s as a bridge called the East London River Crossing, an extension of the North Circular Road; it came back again in the 2000s as a dual carriageway with parallel bus route or tram tracks; and it returned yet again in 2012 as the Gallions Reach Crossing, this time with two traffic lanes and two public transport lanes.
• A local crossing at Belvedere, near Erith, was mooted as a possibility for one of the later stages of the Thamesmead development that did not take place. It was resurrected in 2012 as the Belvedere Crossing, again with two traffic lanes and two bus lanes.

So what is the Silvertown Tunnel?

It's the latest attempt to unblock Blackwall, and successor to the third bore tunnel and then the bridge scheme. It would provide a dual two-lane tunnel immediately east of Blackwall, effectively doubling the number of traffic lanes under the river and removing height restrictions for northbound vehicles. One lane in each direction is proposed to be reserved for buses and HGVs.

At the south end, the new road will merge into the A102 Blackwall Tunnel Southern Approach - a three-lane road with capacity far in excess of the Blackwall Tunnel, so there's room to accommodate additional traffic. At the north end, plans show a slightly disappointing signalised junction that will allow traffic to join the A1020 Lower Lea Crossing, with connections to the A13 and the Docklands.

New road capacity here will be the answer to the prayers of every motorist who queues every day to cross the river, not to mention the many companies who have business on both sides of the river but struggle to get from north to south in a timely manner. It'll make life much easier for hauliers who currently have to divert via Blackwall (or the slow Woolwich Ferry) to avoid the low roof of the northbound Blackwall Tunnel.

What won't answer their prayers will be the "road user charge" - for which read "toll" - that will be introduced on the new Silvertown Tunnel and the existing Blackwall Tunnel to pay for it. The charge will be collected electronically, as at Dartford, and will be matched with the cost of the Dartford Crossing so there's no financial incentive to choose one over the other.

The new tunnel faces still opposition from residents' groups, environmental campaigners and lobbyists promoting public transport and cycling, who see it as a concession to private motoring and a source of increased air pollution on the North Greenwich peninsula.

Will it be built?

Almost certainly yes, now that it has Development Consent. No public inquiry is required or will be held. But the price of its arrival on the TfL road network in a few years' time will be steep.

First is the reputational hit that Sadiq Khan, Mayor of London, has taken for endorsing and pursuing it. His election manifesto made clear that he supported it and he's seeing it through, but since election he's made it his business to clean up London's air - and building new roads is not a universally acknowledged way of doing that. In this case, however, the new tunnel is expected to significantly reduce delays on the approaches to the tunnels, and shorter jams mean fewer engines idling and lower emissions.

Second is the other new infrastructure that's fallen by the wayside to prop it up. Thanks to Khan's pledge to freeze public transport fares, the end of direct Government grants and an unexpected decline in passenger numbers, TfL is facing serious financial pressures at the moment. When Khan became Mayor, there were two other new river crossings in development - Gallions Reach and Belvedere - that had been announced by his predecessor, Boris Johnson. In the last year, those proposals have silently been removed from TfL's website and publicity material no longer discusses them. £2bn has been saved, and Silvertown is the last river crossing still in the game.

Is it worth it?

All of this brings us back to the central question, which is why Silvertown is still being pursued by a public transport organisation that has only built two miles of new road in the eighteen years it has managed all of London's major road infrastructure, and whose main focus on the highway network is in improving the urban environment and lowering traffic speeds.

Further east, at Gallions Reach and Belvedere, the two new bridges were supposed to support new housing development on both sides of the river, in the Thames Gateway region; development that has been on the cards for more than a decade but is still proving stubbornly difficult to get started. Ditching those crossings won't delay an already stalled project, though it won't help it get going any sooner.

The case for Silvertown is different. It’s still to do with population growth, but not directly to do with new housing.

Its purpose is, obviously, to relieve the chronic congestion that plagues the Blackwall Tunnels each day. Blackwall already represents an enormous time penalty on road journeys between South East London and most of the rest of the conurbation, and adds an unacceptable level of uncertainty to journeys. The result is that even with present population levels, the existing tunnels are a noticeable drag on the economy and quality of life in this part of London. They also represent a major air quality problem thanks to the queues that form in the morning rush and last all day - something that must be addressed now the Greenwich Peninsula is beginning to bristle with dozens of new high-rise apartment blocks.

The population of London is forecast to grow by several million in the coming years. Demand for travel across the river will increase with it, and Blackwall will continue to increase in popularity because it is close to central London, has good onwards links in all directions and - perhaps crucially - because it is close to the economic hub of the Docklands.

The point of the Silvertown Tunnel is, therefore, not so much to generate new capacity for any specific new development, but to unblock a serious existing problem in order that it does not become a limiting factor in the ability of South East London to grow. By introducing a “user charge” – or toll – to both the new tunnel and to Blackwall, it’s hoped that journeys that could be made just as easily by other means will be strongly discouraged, and those that really do have to be made by road will be faster and more reliable.

None of that means that Silvertown will be popular. The motoring lobby - in the form of the motoring clubs, the Road Haulage Association, the ABD, and so on - should be the ones to support it and to bolster TfL’s case. But they remain dead set against it if Blackwall will be tolled. The user charge certainly seems a little unfair: it applies a toll to a crossing that has been free since 1897, and it means residents of East London must pay to do something that is, and will continue to be, free for those in the West.

The Silvertown Tunnel is, therefore, absolutely necessary and a clear potential benefit to people across East London, and yet it's very short of supporters. That is ultimately why no new crossings of the Thames have been made in this part of the world since 1959: they might be needed but they have never been popular. And until spades actually hit the ground, Silvertown's future isn't guaranteed, because even the people it's supposed to benefit are unwilling to cheer it on.