The Blackwall Tunnel in East London

[Rooser]

The Northbound tunnel of this particularly ancient and decrepid peice of engineering is so ridiculously bendy that it seems the forefathers of one Uri Gellar had more than a helping hand in it's construction. Why on gods earth does it bend from left to right so ludicrously? Were straight lines "unfashionable" in those days?

[rutineli]

Here we go,.... when I was a boy.....soon after the war when there were still bullet holes sprayed across the glazed white tiles all around the entrances, there were a darn sight more bends and curves in the thing.  There were lots of straightening projects between then and now although I cannot really tell why they should have been necessary.  Traffic was two way then to the best of my memory .

[sddsddean]

I can remember when it was two way as well. If you think its fun driving through it now, try it with an artic!! Its amazing how many cars risk overtaking you! I was always told that the tunnel was built in the London clay strata just below the river bed and that the engineers of the time were worried that the river current (enhanced by the tidal forces) might scour out the clay around the tunnel, so they built it in a double S shape so that if this did happen the current would not roll it down the river! Being an ex Civil Engineer, I am not convinced by this, but can't think of a good reason why it was built in such a way.

[smorodina]

Apparently, the tunnel having been opened in 1897, there was a danger of horses bolting for the light if they saw the exit too early.

[Rooser]

Many thanks for your insights. I like the horses one smorodina, it sounds really rather plausible is suppose.

[Octavius]

When the first Blackwall tunnel was built in 1897 it was designed for horse-drawn carts and carriages.

It had to be curved, rather than straight, simply because the horses would bolt if they saw the light at the end of the tunnel.

 

[trilobite]

I've heard it was to prevent horses bolting, too.

[Tim Baxter]

Surely if horses wear blinkers then the only light they ever see is directly ahead and if this is the case then every horse that ever wore blinkers would make a bolt for the blue??? thus invalidating any reason for not letting them see the light at the endo f the tunnel!!!!

[Octavius]

Auntie wouldn't lie would she...

http://news.bbc.co.uk/1/hi/world/europe/1945581.stm

[vrossi]

Having worked in and around the tunnel for a number of years, I can confirm that the bends were there to prevent the horses bolting for the light at the end. You'll notice that the south bound tunnel, built in the 1950's is a darned sight straighter!