1. Transport
November 23, 2015

No, the Thames is not too wide to build new river crossings in east London

By Jonn Elledge

Travel west from Tower Bridge, and before reaching the M25, London’s orbital motorway, you’ll find some two dozen road crossings over the River Thames.

Make the same count heading east, and you’ll find just three: the ancient narrows of the Rotherhithe Tunnel, the more heavy duty version at Blackwall, and finally the near-motorway greade Dartford Crossing, which combines a tunnel (heading north) with a suspension  bridge (heading south).

This contrasting geography popped into my mind a couple of weeks back at a public meeting organised by the No To The Silvertown Tunnel campaign*. That group is doing a very fine job of making the case that building another tunnel right next to Blackwall would be A Bad Thing for all sorts of reasons (the inability of South London’s existing road network to cope with extra traffic, the horrific toll air pollution is already taking on London’s health, and the fact it would take money away from public transport, to name but three).

But I found one of the campaign’s other arguments rather less convincing. When I mentioned the difficulty of crossing the river in east London, one of the campaign’s organisers suggested that, maybe, this was a sad inevitability. The river was much wider in the east than the west, she said; maybe it would always be an impassable physical barrier.

The first part is true enough: the Thames at Dartford is around 570m wide, compared to around 250m at Tower Bridge, under 100m at Richmond and less than 60m by the time it passes the M25 in the West at Runnymede.

But does that make it impassable? No. Not even slightly.

Transport for London is currently looking at building three more road crossings of the River Thames: the Silvertown Tunnel, a bridge at Gallions Reach and another at Belvedere. (There’s also a Lower Thames Crossing proposed east of Dartford, but that’s outside London and it’s a bit vague where it’ll be, so let’s ignore it.) Here’s a map:

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How wide is the Thames at each of these points? At Silvertown it’s just south of 400m:

At Gallions Reach it’s around 620m:

And by Belvedere, despite being nearer the sea, it’s narrowed again to around 560m:

Those are big numbers compared to most of London’s existing bridges – but they’re not when compared to other urban river crossings elsewhere. In New York City, there are a fair few bridges linking Manhattan and the outer boroughs that are of the same sort of scale:

The Belvedere Bridge would, admittedly, be longer than the Sydney Harbour Bridge:

But Liverpool has two tunnels under the Mersey at a point where the river is more than 1km wide:

In some ways, simply measuring the width of the river is a bit misleading. In east London the Thames is still used by shipping, so any crossing built would need to be either a tunnel, or a bridge high enough to allow ships to pass beneath them. Either way, it’ll be substantially longer than the river is wide.

But that’s true of most crossings built on this sort of scale – and some of them are much, much longer than the Gallions Reach Bridge would be. The Golden Gate Bridge is 1.7km long:

The Humber Bridge is 1.8km:

And the Øresund Bridge – which links Copenhagen, Denmark, to Sweden’s second city, Malmo, and is probably unique in having sparked its own hit TV series – goes on for nearly 8km:

Although if you include the artificial island and the tunnel, the crossing as a whole is nearly twice that:

I should probably stop screenshotting maps of bridges really. Here are some pictures instead. 

The Golden Gate Bridge, California. 

Brooklyn Bridge, New York City.

Sydney Harbour Bridge.

The Humber Bridge, northern England.

But anyway, the point, I hope, is clear. There may be very good reasons not to build more roads in London – the fact the city’s air pollution is killing an estimated 9,500 people a year is a pretty powerful case in itself – but the width of the river in east London is not one of them.

From an engineering point of view it really isn’t that challenging to build more Thames Crossings east of Tower Bridge. The question is where we put them – and what we do with them.

*Actually I was chairing it, so not meant to have an opinion, hence I’m gracing you lot with the benefits of my thoughts on the matter instead. You lucky people.

All images: Getty (photographs) or Google (maps).

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