1/ I am all for major plans and projects if they have a *purpose* - that's why I think the UK's HS2 rail line is not a bad idea. But what about this Boris Johnson bridge to France idea...?
2/ The idea for a road bridge across the channel has no sensible purpose, other than perhaps to show to Macron (who he discussed it with) that the UK's foreign secretary is ridiculous.
3/ Let's look at it from each perspective.
4/ In engineering terms building this thing would be possible, although difficult. Compare it for example to the East Bridge of Denmark's Great Belt link - that main span is 65m above the water. Channel span(s) would need to be 80m or so high. Doable. en.wikipedia.org/wiki/Great_Bel…
5/ Likewise The Channel is about 45m deep near Dover. So driving the piles for it would work. en.wikipedia.org/wiki/English_C…
6/ But then it gets much harder. The Channel is the world's busiest sea for shipping. How are you going to design a bridge to cope with that? How many full size spans are you going to need so ships can pass freely? More than 1 for sure.
7/ Plus how are you going to construct the thing safely while shipping traffic remains unperturbed? Complex. 🛳 🚢 🛥
8/ Then there is the issue of long bridges over water: wind. The Second Severn Crossing has a wind diffusion system en.wikipedia.org/wiki/Second_Se… But that's a cable stay bridge, and this channel bridge would have to be a suspension bridge for the main spans. 80m up. 💨
9/ If you were to actually want to build a road to France you might actually then be better building (at least part of it) in a tunnel. But let's not go there for now because...
10/ THERE IS A TUNNEL ALREADY 💪
11/ OK, you have to put your car or truck on a train to use it. But it exists and runs.
12/ OH and it is NOT RUNNING AT CAPACITY. I cannot find precise stats on how close to capacity it is, but its use - especially for freight trains - has been a disappointment: thelocal.fr/20130620/cut-c…
13/ Meanwhile ferries also still ply their trade perfectly well between Dover and Calais as well.
14/ Theoretically this bridge could drive up the numbers of people who would make trips across The Channel. But the toll for the bridge would be hefty for sure. It might get you across slightly faster than the tunnel does...
15/ Meanwhile the UK currently has the slowest growth in the OECD, and there are questions over the funding of HS2, its other main infrastructure project.
16/ Tax revenue is not really there for something like this and - because the economics are questionable - the private sector ought not touch it.
17/ So: Engineering - fine. Construction - possible. Economics - useless.
18/ This idea is going to go the way of Johnson's Garden Bridge and Island Airport. It won't happen.
19/ All I can then conclude is that Boris wanted to deflect from the real news, namely that Macron had no good news for the UK (and especially its financial services industry) outside the EU's Single Market. Fancy that. theguardian.com/politics/2018/… /ends
