mind the gap!

Regarding the deep level lines, the following photo from Hendon Central should illustrate the clearances.

(click for a larger, higher quality version)

I'll have a look through my collection for any comparable photos from the sub-surface lines.

Edit: I don't have anything useful from the SSL, but I shall endeavour to correct this when I'm out and about tomorrow.

I'm half-tempted to say, "Unfortunately".

I believe we were told during training that a single line tube tunnel is approximately 12 feet wide, and that the cess is 9 inches.

I remember on our first day of stock training, three of us were in the front of a train with one of the trainers, going between Arnos Grove and Oakwood. I'd done the trip on the front quite a few times before, since that was my old working area, but one of the other trainees had never been in the front cab of tube stock. (I think she'd been on the District once.) As we approached the tunnel mouth to Southgate, she exclaimed that we'd never fit in there. *g*

The tunnels on the District line vary a lot in size and shape, but there's usually quite a large clearance. I think the Edgware Road branch has some of the tightest ones on the District.

Platform lengths are one reason - another is Edgware Road's track circuits and point locations; they are only big enough to cope with a train of C stock length.

They do now; just those that aren't D stock.

To be honest, it's always amazed me when hurtling through those tunnels how the trains never hit the sides, especially if you look at the carriage behind! More than likely more of an optical illusion as they appear to wobble so much, and that the speed in the tunnels seems greater.

So you put that to the back of your mind, then watch the train you have just alighted hurtle off down the tunnel and wonder how it all fitted through!

It is (for me) one of the glories of travelling The Tube. Designed so many years ago, and given modern technology, I'll wager it wouldn't even be anywhere near that tight! Yet it's stood the test of time, and passed with colours!

So, if, say, 40 people all on one side of the train simultaneously jumped from one side of the car to the other at a strategic point on the network where clearances are very tight, could they get the car to hit the tunnel wall?

Mmm! I can assure you that its quite an adrenalin rush being in a tube tunnel with a train hurtling towards you, been there and done that on the Northern, Central and Picc lines. H&S these days has outlawed what were once normal traffic hours engineering activities 20 years ago.
To access some areas in traffic hours we often chased a train into a tube tunnel and then when we wanted to return to the platform we waited for a train to pass and then took a brisk walk back in the few seconds that the station starter was automatically maintained at danger.

That is why the kinematic profile of the train used to assess clearances. Though extreme cases could cause problems but it would a matter of risk assessment. If the risk is too much to accept then close the line until the risk is reduced to an acceptable level.

Question of my own - what kind of testing regime or configuration is employed on the test trains loaded with weights? I assume the aim is more to test the performance of the train rather than clearances?

There are definitely some fun bits! One of the better comparisons I can come up with is it's a bit like being on an enclosed water slide - all you can see is the next twist ahead of you, and that's that! Someone had tripped out the headlights on our train the other day, and we made it to Bounds Green before realising what the problem was... during the Southgate stretch I'd simply assumed my eyes were having more trouble than usual adjusting. It made for a very eerie feeling, because leaving Southgate all I could see was the signal up ahead, and it looked as though we weren't moving at all for quite some time.