Bi-directional query

[jopsuk]

at the weekend, I was waiting for a train a Thorpe Bay (which is between Southend and Shoebury). Both platforms had four aspect signals at both ends, and in the Shoebury direction (straight line) there appeared to signals flanking the track as far as I could make out- so I assume the line (at least on this section) is bi-directional, yes?

The signal on my platform at the end from which the train was to come was at double yellow when I arrived. As the train approached, it remained at double yellow. This surprised me. I'd assumed, having not seen bi-di in action, that signals against the direction of travel of a train would all be set at red, especially when a train is in the block?

 

[43106]

You could try the latest edition of Quail Map Track plans - most of them show if a line is capable of bi-directionality, but I've got a reprint of the 1988 East & Anglia Regions edition, which doesn't have it.

 

[Daniel]

From the signalling systems LU use, (and the 3/4 aspect signals on NR parts of LU), that does go against was I am taught to be correct practice.

Strangley we were discussing today, the reprecusions of a 'signal systems failure' - (on LU, where a train has fully passed a signal and the signal is still clear). We are told that when a clear aspect is shown behind a train, it is a "wrong side" (of safe) failure, and in that situation all train movements must cease.
Similarly, our procedures regarding single line working (train locked in)/(train not locked in) both requite a protecting signal at danger, (handsignaller or otherwise).

However, those procedures may be, (and I assume, are) different on NR.

 

[starrymarkb]

Could be repeaters? but do they exist in bi-di installs?

 

[GB]

Could be repeaters? but do they exist in bi-di installs?

Depends on the type of bidi installed. If its full bi-di then probably not, but if its simplified bi-di (Simbids) then you will usually get a distant (R) and outer distant (RR) which obviously wont go back to red as they do not have a red aspect.

 

[ungreat]

at the weekend, I was waiting for a train a Thorpe Bay (which is between Southend and Shoebury). Both platforms had four aspect signals at both ends, and in the Shoebury direction (straight line) there appeared to signals flanking the track as far as I could make out- so I assume the line (at least on this section) is bi-directional, yes?

The signal on my platform at the end from which the train was to come was at double yellow when I arrived. As the train approached, it remained at double yellow. This surprised me. I'd assumed, having not seen bi-di in action, that signals against the direction of travel of a train would all be set at red, especially when a train is in the block?

Sounds like a SPAD indicator..might not be
--- old post above --- --- new post below ---

at the weekend, I was waiting for a train a Thorpe Bay (which is between Southend and Shoebury). Both platforms had four aspect signals at both ends, and in the Shoebury direction (straight line) there appeared to signals flanking the track as far as I could make out- so I assume the line (at least on this section) is bi-directional, yes?

The signal on my platform at the end from which the train was to come was at double yellow when I arrived. As the train approached, it remained at double yellow. This surprised me. I'd assumed, having not seen bi-di in action, that signals against the direction of travel of a train would all be set at red, especially when a train is in the block?

it would stay at double yellow..if nothing was in front for two signals

 

[Old Timer]

The signals for the Bi-Directional (Bi-Di) section of the line which display aspects for movements against the normal flow of traffic, respond only to the signal aspect of the signal ahead. They do not respond to track circuit activation until a route is called in the Bi-Di direction.

Signals in the normal direction on Bi-Di lines function normally.

This is so as not to cause signals for the Bi-Di line to be seen changing aspect by a Driver passing over the other line. That is, he will not see the signals on the opposite line changing as a train travelling from the opposite direction is approaching.

 

[hairyhandedfool]

I suspect it is Simbids, I would expect signals in the wrong direction to be held at red (to prevent against a head on accident whilst remaining constant to avoid confusion) therefore it must be an outer distant signal.

 

[mr_moo]

According to the current signal plans, Thorpe Bay has signals on both ends of the Up Main (going towards London) but only on the Down direction on the Down line (towards Shoeburyness).

On the Up line, the 'wrong direction' signal is listed as 587RR. This is an 'outer distant' for the 'wrong direction' move, and can only show a green or a double yellow. Thus, as the train came along in the right direction, it was already displaying its most restrictive aspect, and will always do so until signal 587 towards Shoeburyness is cleared, in which case it will show green.

The bi-di signalling on this stretch is indeed simbids, on both tracks.

HTH!