710112 collision with Buffers at Liverpool Street Station (15/10/2026)

[Efini92]

Not on my signalling drawings they don’t, but happy to be wrong!

I’m pretty sure you’re correct. Isn’t that why all the buffer stop grids are of the smaller type.
I recall the original ones kept having spurious interventions because the timer would reset before the trigger loop was reached.

 

[357]

I’m pretty sure you’re correct. Isn’t that why all the buffer stop grids are of the smaller type.
I recall the original ones kept having spurious interventions because the timer would reset before the trigger loop was reached.

The timer should reset before the trigger loop is reached - it's reaching the trigger loop before the timer resets that trips you isn't it?

 

[edwin_m]

I’m pretty sure you’re correct. Isn’t that why all the buffer stop grids are of the smaller type.
I recall the original ones kept having spurious interventions because the timer would reset before the trigger loop was reached.

It was related to the shape of the electromagnetic field produced by the loops - known as "side lobes". This didn't matter at normal speeds but when they tried to use it for buffer stops (which it was never designed for) it wasn't possible to get the timing accurate enough.

 

[Efini92]

The timer should reset before the trigger loop is reached - it's reaching the trigger loop before the timer resets that trips you isn't it?

No the timer should time out. If the clock resets then you hit the arm loop, it thinks the train is travelling faster than it is.

 

[357]

No the timer should time out. If the clock resets then you hit the arm loop, it thinks the train is travelling faster than it is.

I think we are both saying the same thing but using different terminology!

My understanding has always been that when the train goes over the first loop the timer starts, then the timer should end before you reach the second loop.

If you reach the second loop before the timer ends, you'll have a brake application because you passed between the two racks too quickly.

Tell me if I'm wrong!

 

[PudseyBearHST]

You both are saying the same thing I think.

Are the mini grids different frequency to the normal grids which cause freight train and passenger train to be set at the same speed? Or is it different 10/12.5 or whatever?

 

[Signal Head]

Thanks


Thanks, yes I know it’s recommended to do 8 but the grids are usually set at 12.5mph for freight/10mph for passenger (is that right?) so was wondering if Liverpool Street was different as that was what it sounded like in the message.

Originally set at 10mph (Passr), but there were 'false' interventions on trains running at or very close to that speed. In part caused by the signal from the loops being reflected back by the platform causing the antenna to encounter the 'trigger' frequency a little too early and so appearing to be doing a higher speed.

To counter the problem, 'mini loops' were designed specifically for use in platforms, and the 'set speed' increased slightly to 12.5mph to provide a suitable margin for error.

 

[Efini92]

I think we are both saying the same thing but using different terminology!

My understanding has always been that when the train goes over the first loop the timer starts, then the timer should end before you reach the second loop.

If you reach the second loop before the timer ends, you'll have a brake application because you passed between the two racks too quickly.

Tell me if I'm wrong!

Yeah we are apologies.

 

[RGM654]

Well 6 foot isn't exactly a coach length...

Sorry for belated reply as I was out all day Friday. 6 foot is indeed not a coach length. Trains presumably could stop a few feet from the buffers but they often stop a coach length or more away. I was womdering why.

 

[dk1]

Sorry for belated reply as I was out all day Friday. 6 foot is indeed not a coach length. Trains presumably could stop a few feet from the buffers but they often stop a coach length or more away. I was womdering why.

It can often depend on which class of train & include things like stopping points for pantographs such as platform 1 at Ipswich as the OHL does not run the full length of the platform and as an example to stop a station roof pillar or other furniture from blocking wheelchair ramp access at train doors. Platform 6 at Norwich is another issue for 755/3s. They stop further back as if not the opposite cab stands over the TPWS grid.

At Liverpool St in certain platforms such as platform 8 a 12-car train needs to get fairly close to the stops or it will stand foul at the rear.

 

[rogercov]

Not my photo!

And slightly more recent (my photos)
Amazing that it had hardly changed in over 60 years!

 

[bahnause]

I wonder if the over restrictive driving required coming into terminal platforms gives the opportunity for a driver to become distracted?

That is indeed a problem. Recently, an SBB task force tasked with preventing irregularities in shunting operations imposed a reduction in speeds on a trial basis. Of course, this was done without any accompanying measures or consultation with the infrastructure operator. The impact on operations was so severe that the trial had to be abandoned after a short time. In other words, nothing that an employee familiar with rail operations and possessing half a functioning brain cell could not have foreseen.

Another reason for ending the trial was that the low speeds and extended driving times for no reason caused concentration to wane, and the pressure to make up for lost time was simply shifted to the next tasks. Again, nothing truly surprising that would have justified such a hasty decision. But it was marketed as a “valuable insight.”

 

[172007]

Changed my mind and deleted comment.

 

[CyrusWuff]

Platforms 1 & 2 at Liverpool Street are (still?) closed today and showing as under T3 possession on Traksy.

 

[saismee]

Platforms 1 & 2 at Liverpool Street are (still?) closed today and showing as under T3 possession on Traksy.

Expected to be back for tomorrow morning.

 

[Bald Rick]

Platforms 1 & 2 at Liverpool Street are (still?) closed today and showing as under T3 possession on Traksy.

Because of engineering works elsewhere over the weekend, there was a reduced service into Liverpool St. No need to hurry with repairs, so it could be done without cancelling other works. Will be all back in the morning.