Sunday, 9 March 2014

Mysterious bridge near King's Cross

On the train down from King's Cross on Friday, just north of the station, we went past a construction site by this strange bridge crossing overhead.

It looks to me as though it carries a railway, but it's too far north to be Crossrail (which is in tunnel in central London anyway). Does anyone know what this is, and why it's in the form of a tube?

Later on the journey our train used a new rail crossover viaduct. On the way up to King's Cross I'd noticed the new embankment twisting away to the right.

The clouds were interesting too, with flat bases. I should know what this signifies, but I've forgotten. It's not something to do with temperature inversion, is it?


Nb Duxllandyn said...

The tubular bridge carries the High Speed lines from Kent and Eutotunnel on their way into St Pancras. They rise from underground and cross the bridge inside the tube. No idea why that is necessary though.

Nb Duxllandyn

Frank Clarijs said...

this is the bridge I guess,-0.1227463,208m/data=!3m1!1e3
I agree it is a strange contraption. The only reason I see is that the line to the east goes into a tunnel and the engineers could not (in the restricted space) make a proper tunnel entrance after the bridge, so they use the bridge for that purpose, eliminating risk of rain etc to enter the tunnel.
And also this might be part of the special security measures for HS1, to avoid that dangerous continentals like me enter the country without proper security checks.

Halfie said...

Thanks Mike and Frank. Now, why didn't I think of looking at Google Maps?

Paul (from Waterway Routes) said...

The reason for the "tunnel" is that without it the train would exit one real tunnel into a very short section of daylight then another real tunnel.

We all know what happens entering a canal tunnel when your eyes take time to adjust to the dark and you can't see anything for a few seconds.

The continuous "tunnel" ensures train drivers can continuously observe where they are going and see signals and their cab displays properly.

Halfie said...

Wow! Thanks Paul. I hadn't thought of that.