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On 18th of January 2018, Boris Johnson (the UK's poster boy for the descent of man) reanimated the long-buried corpse of a possible road bridge across the English Channel.
This idea came to him whilst he was fraternising with delegates at an Anglo-French summit headed up by Emmanuel Macron, who presumably plied him with Bordeaux before goading him into tweeting the silliest thing that came into his head.
I'd suggest that this picture backs up my interpretation of events:
En marche ! Great meetings with French counterparts today pic.twitter.com/D73B1rSkd3
— Boris Johnson (@BorisJohnson) January 18, 2018
If we park the fact that Boris the Bullet-dodger was using this ridiculous announcement to drown out talk of how badly the battle for Brexit is going, I'd like to briefly dissect the idea of the cross-Channel motorway bridge:
Hardly an original idea
The idea is certainly not a new one, with formal plans having been drawn up on both sides of the Channel on successive occasions. In all cases, the proposals were ditched.
Boris, a big fan of backing fantasy projects against a wall of contrary evidence, seems to have been characteristically undeterred by historical precedent.
Mark Hansford, editor of New Civil Engineer, had this to say about the potential megaproject:
It would be a magnificent iconic structure and a fantastic symbol of unity in a post-Brexit world.
Mark Hansford, The Local (19 January 2018)
Other engineers were quick to suggest that it would be technically possible, if challenging.
This isn't a great take, to be honest...
As engineers, it is our moral duty to speak up when an idea as profoundly stupid as this reaches the public forum.
What would it be for?
The fastest current choice for travellers between Kent and mainland Europe – the Channel Tunnel and its connecting high speed railway lines – is not yet at capacity so there's actually no pressing need for a new connection.
If further capacity was required at some point in the future, then this would be far better served by additional bores utilising all of the existing railway infrastructure around the tunnel portals, as well as all of the detailed survey information that was used in the original design.
Put simply, it would be cheaper and more environmentally friendly to bore another tunnel if needed.
It took several failed attempts to finally drive a railway tunnel between the UK and France, with the first digging taking place as far back as 1881. This scheme was spearheaded by one the greatest railway strategists of all time, Sir Edward Watkin, who also built the UK's first high speed, long distance railway in the form of the Great Central Main Line (yeah, he was pretty ahead of his time).
All sorts of problems
A motorway bridge would introduce all sorts of challenges... Road vehicles such as cars and HGVs aren't very predictable or safe compared to trains moving on fixed rails protected by signals and this causes all sorts of trouble when there's a crash or other incident on such an isolated piece of infrastructure.
Looking at the benefits for users of staying in the car when compared to making the journey via the railway: drivers would still have to queue for customs (undoubtedly made worse after Brexit) and speed limits would likely have to be restricted over the bridge for safety reasons (perhaps to 50mph or less).
The speed restriction for trains going through the Channel Tunnel is 160km/h, which is double this.
I daresay that with the inevitable tolls required to pay for this thing, it wouldn't be much quicker than queuing to get onto Le Shuttle (the train that currently carries road vehicles through the Chunnel).
In terms of comparative capacity: one train can carry as much as 80 lorries worth of goods. It is a similar story when comparing passenger capacity. This would be compounded by the need to restrict speeds for a road crossing for safety reasons.
The shipping problem is a major one... All previous designs of cross-channel bridge included a tunnel section to avoid blocking what is literally the world's busiest waterway.
Unlike a tunnel, this overdesigned game of container ship skittles would be susceptible to inclement weather conditions, too. Even the best wind-shielding doesn't compare with burying the whole lot under the sea.
Would it be worth it?
Most fundamentally of all, as our economy continues to falter in the wake of our country winning back its right to import bendy bananas, should we really be spending billions of pounds on private/unsustainable transport infrastructure?
Some might argue that ticket prices on Eurostar and Le Shuttle could hardly be called affordable. I completely agree. Why not take a fraction of the price tag of the road bridge and offer heavily-subsidised fares through the Channel Tunnel?
Engineers can always make something work. It's just that sometimes there are better ways to spend the money.
In any case, engineering projects normally fail if the solution comes before the problem.
The Boris Bridge... Possible: yes. Rational: no.
Gareth is an engineer and writer, specialising in railway systems. As well as roles in design consultancy, he has written for several technical journals and for the railway press. He leads the York section of his professional institution, as well as being a lecturer in track systems at a newly-opened national engineering college.
