Signals protecting level crossings

[michael769]

I noticed this morning as my train pulled into Kirknewton station over the level crossing that the signal for the other line was showing caution.

I was slightly surprised to see the crossing barriers lift and traffic start crossing even though the signal continued to show caution.

I had always assumed that the signals on approach to an AHB protected the crossing?

 

[edwin_m]

No, all the automatic crossing types are independent of the signalling although the signaller can replace the protecting signals to danger in an emergency and gets a failure alarm for remotely monitored types. Some automatic crossings at the departure end of platforms have a special control so a stopping train can run in with the crossing open to road traffic and the signal at red, with the barrier sequence being started in time for the train to depart.

Only manual crossings (with an operator present or watching via CCTV, or more recently an automatic obstacle detector) are interlocked with the signals. These types are the only ones that have full width barriers. They also close a lot longer for each train, as they need to be closed and the protecting signals cleared in time to give the train a run through on greens.

 

[A-driver]

A good example of different types is foxton & shepreth on the Cambridge-Hitchin line. Foxton is manually controlled by a crossing keeper on site. Therefore once the barriers are confirmed down and the crossing seen to be safe the signals can be cleared. The signaller informs the crossing keeper if the next train is stopping or not so the crossing can be lowered without slowing a fast train. On the down road a fast train will approach a single yellow signal 2 signals before foxton crossing but it SHOULD go to green just before you reach it.

At shepreth it's an auto crossing. The signaller switches between fast train and slow train mode and that makes the appropriate set of treadles work. So if in fast mode the signal can be cleared and the train will activate the first set of treadles further from the crossing. It, therefore, shouldnt encounter any restrictive signals due to the crossing. In stopping train mode the signal on the end of the platform will be held at danger and the treadles used are within the platform. Therefor a stopping train actually approaches shepreth in the up with the crossing raised and cars driving across as you drive into the platform and open the doors. In my opinion not the safest way of working-especially in the leaf fall when that station can be pretty slippy.

 

[scotraildriver]

But previously that signal would always be at danger until the driver operated the plunger to activate the crossing, then it would clear so effectively protected the crossing (As at Kingsknowe). Not so now since signals renewed.

 

[Railsigns]

But previously that signal would always be at danger until the driver operated the plunger to activate the crossing

Only if it's a "stopping" train. Drivers of "non stopping" trains don't use the plunger. The signalman will operate the "stopping"/"non stopping" control for each train to determine how the crossing will behave.

 

[michael769]

But previously that signal would always be at danger until the driver operated the plunger to activate the crossing, then it would clear so effectively protected the crossing (As at Kingsknowe). Not so now since signals renewed.

I though the signal renewal was being done at the end of May along with the crossing upgrade and Midcalder Jn Remodelling?

 

[Tomnick]

In my opinion not the safest way of working-especially in the leaf fall when that station can be pretty slippy.

One of the precautions taken following a report of poor railhead conditions is to select 'non-stopping' for any such AHBs, even for a stopping train. At other times, it makes sense to suppress the sequence for stopping trains - one of the big risks, of course, being that folk will get impatient and zig-zag around the barriers if they're down too long (especially if they see the train come to a stand in the platform - not considering what might be approaching on the other road!)