Chiltern operations at Amersham

[Deleted]

With regards to the thread on the Class 168 tripcocks and a thread on uk.railway, I have a few questions about Amersham station and how Chiltern use it:

1. The thread states that north of Amersham, no one really knows what the line speed is supposed to be for Chiltern services. Some think that it is 60 like the rest of the Met Main, while others say that it used to be 70 and that many drivers attempt to reach 70 before Mantles Wood Junction. What is the canonical speed limit between Amersham and Mantles Wood?

2. Why is the tripcock tester located on the up platform at Amersham? Shouldn't there be a tripcock tester at Great Missenden, so that trains that fail the test can be reversed south to north on the trailing crossover instead of risking a SPAD upon entering LU territory? Some of the threads I've read on uk.r and u.t.l. state that a tripcock tester can't be installed at Great Missenden because it isn't on LUL territory (yet there is supposedly a tripcock tester at Finsbury Park for the GN&CR services that go 'down the hole').

3. How many aspects does JW1 have? Most of the stuff I've read states that JW1 is a three-aspect signal; yet the view from the level crossing implies a four-aspect signal...

[Harsig]

theonekea said:

With regards to the thread on the Class 168 tripcocks and a thread on uk.railway, I have a few questions about Amersham station and how Chiltern use it:


3. How many aspects does JW1 have? Most of the stuff I've read states that JW1 is a three-aspect signal; yet the view from the level crossing implies a four-aspect signal...

I don't know where you do your reading, because everything I've ever read, seen or otherwise been aware of has shown that JW1 was, is and probably always will be, four aspect.

[Deleted]

Really? I was on the level crossing a few years ago and the external casing for JW1 was of a different size and shape; when I found myself back on the level crossing the casing appeared much as it does now. Was the signal relamped recently?

Naturally of course I can never put my hands on anything when I want, so I can't say for sure where I got the idea that JW1 was not four-aspect - I suspect it had something to do with the original external casing. When I went past the signal earlier this year on an up Chiltern service, it was definitely four-aspect.

[Deleted]

theonekea said:

1. The thread states that north of Amersham, no one really knows what the line speed is supposed to be for Chiltern services. Some think that it is 60 like the rest of the Met Main, while others say that it used to be 70 and that many drivers attempt to reach 70 before Mantles Wood Junction. What is the canonical speed limit between Amersham and Mantles Wood?

The line speed is 60mph from just after Amersham Station, until it rises to 75mph near Fullers Hill Tunnel and it stays this way until the 35mph restrition just before the platforms at Aylesbury.

Why is the tripcock tester located on the up platform at Amersham? Shouldn't there be a tripcock tester at Great Missenden, so that trains that fail the test can be reversed south to north on the trailing crossover instead of risking a SPAD upon entering LU territory? Some of the threads I've read on uk.r and u.t.l. state that a tripcock tester can't be installed at Great Missenden because it isn't on LUL territory

Why would there be a risk of a SPAD at Amersham if the train failed a tripcock test? If the signal was red, the train would be stopping anyway, and if the signal was green, there wouldnt be an issue.

Even if the train was to fail the tripcock tester, as there is a 10mph maximum speed over the testers anyway, the train would be able to stop before the signal, to have it put back, to facilitate a South to North shunt.

theonekea said:

How many aspects does JW1 have? Most of the stuff I've read states that JW1 is a three-aspect signal; yet the view from the level crossing implies a four-aspect signal...

It is certainly a 4 aspect signal.

You have to remember that what is posted on UKR & UTL, is not always accurate and 100% correct, and shouldnt be taken as Gospel.

[Deleted]

metapprentice said:

theonekea said:

1. The thread states that north of Amersham, no one really knows what the line speed is supposed to be for Chiltern services. Some think that it is 60 like the rest of the Met Main, while others say that it used to be 70 and that many drivers attempt to reach 70 before Mantles Wood Junction. What is the canonical speed limit between Amersham and Mantles Wood?

The line speed is 60mph from just after Amersham Station, until it rises to 75mph near Fullers Hill Tunnel and it stays this way until the 35mph restrition just before the platforms at Aylesbury.

Thanks.

metapprentice said:

Why would there be a risk of a SPAD at Amersham if the train failed a tripcock test? If the signal was red, the train would be stopping anyway, and if the signal was green, there wouldnt be an issue.

True, but I'm looking at it from the perspective of a 16X with a failed tripcock SPADding JW1 and risking the lives of people on the level crossing. But I suppose you're correct, and that it isn't an issue at all.

metapprentice said:

Even if the train was to fail the tripcock tester, as there is a 10mph maximum speed over the testers anyway, the train would be able to stop before the signal, to have it put back, to facilitate a South to North shunt.

Via one of the electrified sidings, or via 34RD?

metapprentice said:

theonekea said:

How many aspects does JW1 have? Most of the stuff I've read states that JW1 is a three-aspect signal; yet the view from the level crossing implies a four-aspect signal...

It is certainly a 4 aspect signal.

Thanks. I had a feeling I was wrong about the number of aspects, which is why I asked

metapprentice said:

You have to remember that what is posted on UKR & UTL, is not always accurate and 100% correct, and shouldnt be taken as Gospel.

I don't ever take anything posted on the Internet as gospel, especially not in Usenet - that's why I made this thread

[Deleted]

theonekea said:

True, but I'm looking at it from the perspective of a 16X with a failed tripcock SPADding JW1 and risking the lives of people on the level crossing. But I suppose you're correct, and that it isn't an issue at all.

The crossing in question is Mantles Wood Foot Crossing, and as that is all it is, there is not a requirement of interlocking between the crossing and the signalling, like there would be with a road crossing.

In any case I suspect that even if the train was tripped by JW1, the train would be able to stop from normal line speed and still be short of the crossing.

theonekea said:

Via one of the electrified sidings, or via 34RD?

I would suspect via 34rd, otherwise you have to do a double shunt!

[Deleted]

metapprentice said:

theonekea said:

True, but I'm looking at it from the perspective of a 16X with a failed tripcock SPADding JW1 and risking the lives of people on the level crossing. But I suppose you're correct, and that it isn't an issue at all.

The crossing in question is Mantles Wood Foot Crossing, and as that is all it is, there is not a requirement of interlocking between the crossing and the signalling, like there would be with a road crossing.

In any case I suspect that even if the train was tripped by JW1, the train would be able to stop from normal line speed and still be short of the crossing.

I suppose so - the trainstop and signal are level with one another, and both appear to be approx. 10/15m from the crossing.

metapprentice said:

theonekea said:

Via one of the electrified sidings, or via 34RD?

I would suspect via 34rd, otherwise you have to do a double shunt!

Ah - I had forgotten that you could access 34RD from the center and up platform. It's just not the down platform that you can access 34RD from, right?

[Deleted]

theonekea said:

Ah - I had forgotten that you could access 34RD from the center and up platform. It's just not the down platform that you can access 34RD from, right?

Correct