Loss of power in ATO

I believe the brakes will be applied immediately. The driver would then go into coded manual and drive it manually into the platform.

Qoute from Graeme Bruce (Tube Trains under London)

"The ultimate safety device is the trip valve. It is fail-safe in that it is held up electrically, and should the supply fail then the emergency brakes are applied automatically."

Yes Phil but it all depends on what power supply is keeping the CTV energised. If it's from the train batteries (which I believe it is) what difference will the traction supply going off have on the CTV feed?

IIRC on the Central line the trains attempt to loadshed after traction is isolated which results in the train coming to an abrupt halt but on the Victoria line the traction current is irrelavent unless you lose code or the CTV feed is lost, causing the CTV to drop away.

Code Trip Valve.

On 1967 Tube Stock it is the train-side mechanism which helps to replace the tripcock on conventional LU signalling. During normal operation (i.e. Auto) the CTV detects the coded impulses in the track and remains closed, allowing the train to motor and the brakes to be worked normally. When the code detection is lost, the CTV opens, cuts out the motors and applies the brakes. During Manual mode, the CTV also opens if train speed exceeds 25mph; this is due to the fact that the ATP on the Victoria Line can't tell the driver what the code is in the next block section.

(fx: stampede of T/Ops and AETs coming to poke holes)

Whilst I don't know the answer to the original question - i'd just like to pick up on the SCD question here.....

Whenever possible, short circuiting device's must always be placed at both ends of the train. That instruction has not changed with opo, and applies regardless of wether the train may or may not be bridging a gap.

If the traction current goes off whilst a train is travelling in ATO, the train will loose motors and then coast. After 50 seconds the emergency brake will be applied as the train then starts to Loadshed.

The reason there is a 50 second delay is because the Traction Current often goes off on overload and is back on within in seconds, which would mean an immediate EMCY brake application would be a tad pointless.

The train should stop before the 50 seconds is close, as the Train Operator should apply the emergency brake as soon as he is aware that the Traction Current is off, and has been for more than a few seconds.

And as Double Trigger rightly says, if there is no power, how would the Train Operator be able to drive the train in CM? Coded is no different to ATO, apart from the fact the computer isnt controlling the train

Hmm, a bit different from the District then! We can coast as long as we like without traction current, and in open section we might go more than 50 seconds without noticing the current had gone off.

In fact, I'd try to coast to the next station. I'm not aware of any instruction to the contrary, although I may be about to be corrected!

Quote me if I am wrong, but isnt that one way of dealing with no traction current? Coast as far as possible?

Although it probably helps if you are travelling downhill !

I had the current go once when I'd just left Blackfriars. I was only doing about 10-15 mph and it managed (just!) to coast to Temple. Glad I did, because we had to wait about 5 minutes at Temple for it come back.

Refurb D stocks have loadshed too - would that prevent coasting once it kicks in?

Thanks everyone, lots of input on this one. I remember leaving Newbury Pk with a 62ts and the power went off just as I past the rail gap indicator and was entering the tunnel,and manged to coast to Gants Hill. Is that gap still their, if memory serves me right there was also a rail gap repeater on or near the stater at that location.

Isn't the instruction to coast to the next station unless you meet a rail gap, in which case you should drop anchor immediately?