Metropolitan fast train running on slow line

[miklcct]

I boarded a Chesham fast today in the evening. However, after passing Harrow on the Hill, it didn't enter the fast line but remained on the slow line, and ended up with a crawl because a Watford semi-fast was not long before.

Why didn't the train use the fast line? Shouldn't the driver reject the route if the train is fast but signalled onto the slow?

 

[yorkie]

I boarded a Chesham fast today in the evening. However, after passing Harrow on the Hill, it didn't enter the fast line but remained on the slow line, and ended up with a crawl because a Watford semi-fast was not long before.

Why didn't the train use the fast line?

Engineering possession? All sorts of possible reasons!

Shouldn't the driver reject the route if the train is fast but signalled onto the slow?

Why? You surely can't be serious; that would make absolutely no sense whatsoever.

 

[Dstock7080]

The Harrow hot-weather-plan was in operation yesterday from 16.33-20.26, so that all trains would use the local lines

 

[Bletchleyite]

The Harrow hot-weather-plan was in operation yesterday from 16.33-20.26, so that all trains would use the local lines

Hot weather plan? It was twelve degrees.

Do LU retension the rails twice a year?

 

[Dstock7080]

Do LU retension the rails twice a year?

i haven't seen that done on LU/LT for many years. in the days of 60' bullhead it was a regular job, flat-bottomed doesn't require re-tensioning.

 

[Mojo]

Hot weather plan? It was twelve degrees.

Do LU retension the rails twice a year?

It’s nothing to do with the air temperature and also nothing to do with the rails - this plan is in place all year long and during the summer people will see this on many days. Automatic detection equipment measures the critical rail temperature and it is brought in any time the CRT exceeds 27 degrees.

It’s about minimising the use of certain sets of points at Harrow on the Hill to prevent failures.

 

[Bletchleyite]

It’s nothing to do with the air temperature and also nothing to do with the rails - this plan is in place all year long and during the summer people will see this on many days. Automatic detection equipment measures the critical rail temperature and it is brought in any time the CRT exceeds 27 degrees.

It’s about minimising the use of certain sets of points at Harrow on the Hill to prevent failures.

Thanks. Interesting!

 

[DavyCrocket]

Engineering possession? All sorts of possible reasons!

Why? You surely can't be serious; that would make absolutely no sense whatsoever.

Absolutely the Train Operator should stop to the rear of the signal in these circumstances and contact signaller or controller unless they had previously been made aware otherwise.

 

[DanNCL]

Absolutely the Train Operator should stop to the rear of the signal in these circumstances and contact signaller or controller unless they had previously been made aware otherwise.

Not for being routed on the slow instead of the fast.

 

[Taunton]

The Harrow hot-weather-plan was in operation yesterday from 16.33-20.26, so that all trains would use the local lines

Come on. I had to switch the heating back on in the house yesterday late afternoon.

Hot weather machine defective?

 

[MikeWh]

Hot weather machine defective?

As explained above, it's a plan (not a machine) that is activated when the rail temperature exceeds a certain amount. This does not necessarily correlate to hot air temperature.

 

[Taunton]

OK, for 'hot weather machine' read thermometer.

If not from air temperature. where else can the heat come from? Direct solar gain? We're only just past the Spring equinox, two months to go to midsummer day. Plus yesterday was somewhat overcast.

 

[MikeWh]

where else can the heat come from?

Friction

 

[Hadders]

It's also possible that this was a 'rehersal' ahead of (hopefully) warmer summer weather.

 

[Snow1964]

It’s nothing to do with the air temperature and also nothing to do with the rails - this plan is in place all year long and during the summer people will see this on many days. Automatic detection equipment measures the critical rail temperature and it is brought in any time the CRT exceeds 27 degrees.

It’s about minimising the use of certain sets of points at Harrow on the Hill to prevent failures.

Thank you for explanation

Seeing as rail heads can often be 10-15c higher than air temperature on sunny summer days, does seem odd that the points have only been specified so that might be iffy 4 months of the year.

 

[miklcct]

The Harrow hot-weather-plan was in operation yesterday from 16.33-20.26, so that all trains would use the local lines

OK, does this actually mean that the timetable is written in a way to allow a fast train using the slow line? If so what's the point of having fast trains? If not wouldn't this result in a minor delays of the line to be sent through the TfL status?

 

[edwin_m]

It’s nothing to do with the air temperature and also nothing to do with the rails - this plan is in place all year long and during the summer people will see this on many days. Automatic detection equipment measures the critical rail temperature and it is brought in any time the CRT exceeds 27 degrees.

It’s about minimising the use of certain sets of points at Harrow on the Hill to prevent failures.

The CRT is the maximum temperature the rail can tolerate without special measures due to risk of buckling. It's related to the tension or compression in the rail but also to how well the track is restrained by the ballast. Are the sensors really measuring CRT (I think this can only be done by measuring rail stress and making some assumptions about track restraint). Or are they measuring actual rail temperature and comparing it to a pre-calculated CRT?

If the plan takes certain points out of use then it sounds like the problem is the condition of these points making them susceptible to failure due to rail expansion or some other temperature effect. If this happens at a rail temperature as low as 27degC then the condition is likely to be pretty poor!

 

[Dstock7080]

OK, does this actually mean that the timetable is written in a way to allow a fast train using the slow line?

Amersham/Chesham trains would be behind a Watford and lose a maximum of about 4½mins by Rickmansworth, ample recovery time at terminal for departure.

 

[A60stock]

Whilst I am well aware that a fast caught up behind a slow would not lose much time in the context of recovery time, 4.5mins is a lot in the context of the train being a fast train. So as queried before, would it not make sense to just run anything which is going to get caught behind a slow, all stations anyway as the time difference would not be much? (Note that a train which has a "clear" run would remain fast). I know passengers may get annoyed at a fast train becoming all stations from Harrow at the drop of a penny, but the driver should be instructed to say that as we have to use the slow lines, the train would be caught up behind an all stations and be going very slow.

Some options:

1. Have a hot weather timetable in place which makes amendments to when fast trains depart Harrow on the hill (obviously accounting for Chiltern trains) so that as many as possible get a clear run. I know it needs to be put in place quite last minute but we are only talking about minutes here and there.
2. Give fast trains the priority at harrow if there is one due either just minutes after the all stations or, a stopper and fast get to harrow at the same time.
3. RENEW THE POINTS!!!!!!!!! (So that this isn't an issue). Are there even any other points on the network which have such an issue (which cause significant changes to operations?)

Note with everything I've said above, I realise I am only talking about the evening peak, but the same would apply to the morning peak around the Moor Park junction where the Watford branch diverges. (Potentially a bigger issue for fast trains being slowed as people are getting to work!)

 

[Snow1964]

3. RENEW THE POINTS!!!!!!!!! (So that this isn't an issue). Are there even any other points on the network which have such an issue (which cause significant changes to operations?)

There are hundreds on points on the LU network, and if this one set is so poor it needs special timetables on warm days, you do wonder why they are deemed special so that an alternative timetable and passenger delays are preferred over fixing the problem.

 

[Dstock7080]

there isn’t a special timetable on warm days and at what time would you implement it?

 

[A60stock]

There are hundreds on points on the LU network, and if this one set is so poor it needs special timetables on warm days, you do wonder why they are deemed special so that an alternative timetable and passenger delays are preferred over fixing the problem.

True, then why not just renew this set as its clearly a very bad one which causes changes in operations. Is there another line where a set of points aren't used in hot weather?

there isn’t a special timetable on warm days and at what time would you implement it?

I know, I said there should be one. I guess TFL would need to make that decision in the early morning based on predicted temperatures, so if its anything above 25 degrees, bring the timetable in. In cases where its a last minute decision, you just dont use the timetable.

The cynic in me feels like this is a way to excuse entirely remove fast trains in the future

 

[Daniel]

The set of points is not very bad - they are a different type of points. Moveable angle points are fitted at this location, allowing faster running for trains non-stopping (Chiltern). However, they are more prone to failing to detect owing to expansion so they are taken out of use to prevent delays caused by their use when a warning is given.

This is nothing to do with any hidden plan to remove fast trains - this plan has been in place for decades. What I haven't yet seen mentioned in this thread is that on the local lines between Harrow and Moor Park, unlike convention on the underground the station starting signals do not have short overlaps meaning trains running fast via the local don't have to slow down to 5mph past the station starter. This is because the area is designed for this possibility.

 

[A60stock]

Just had a think back and remembered the issue only used to affect southbound fast trains as it was the harrow north junction which was taken out of use - Therefore northbound fasts could use the set of points south of harrow into platform 1 at harrow on the hill.

However, the south junction isn't used either now during the hot weather plan, when for decades it was. Why has this changed recently?

 

[Jimini]

The set of points is not very bad - they are a different type of points. Moveable angle points are fitted at this location, allowing faster running for trains non-stopping (Chiltern). However, they are more prone to failing to detect owing to expansion so they are taken out of use to prevent delays caused by their use when a warning is given.

This is nothing to do with any hidden plan to remove fast trains - this plan has been in place for decades. What I haven't yet seen mentioned in this thread is that on the local lines between Harrow and Moor Park, unlike convention on the underground the station starting signals do not have short overlaps meaning trains running fast via the local don't have to slow down to 5mph past the station starter. This is because the area is designed for this possibility.

A fascinating post. Thanks for sharing.

 

[zwk500]

The set of points is not very bad - they are a different type of points. Moveable angle points are fitted at this location, allowing faster running for trains non-stopping (Chiltern). However, they are more prone to failing to detect owing to expansion so they are taken out of use to prevent delays caused by their use when a warning is given.

Is this the same thing as a switched diamond (also occasionally called moveable angles on the mainline but normally not considered 'points')?

 

[Daniel]

Is this the same thing as a switched diamond (also occasionally called moveable angles on the mainline but normally not considered 'points')?

Wikipedia suggests they're the same, yes:

Switched diamonds, which contain two stub turnouts in disguise, count as facing turnouts in both directions and are also known as moveable angles (UK).

For the tube, they still need manually securing in the event of a failure so are treated as points in that regard. The MA section of the points work in tandem with the switch blade end of the points on the same lever so are just treated as part of the same equipment if that makes sense.

 

[zwk500]

For the tube, they still need manually securing in the event of a failure so are treated as points in that regard. The MA section of the points work in tandem with the switch blade end of the points on the same lever so are just treated as part of the same equipment if that makes sense.

Yes that all makes sense, and lines up with my understanding of NR practice as well.

 

[edwin_m]

The set of points is not very bad - they are a different type of points. Moveable angle points are fitted at this location, allowing faster running for trains non-stopping (Chiltern). However, they are more prone to failing to detect owing to expansion so they are taken out of use to prevent delays caused by their use when a warning is given.

There are hundreds of switch diamonds across the national network, they aren't particularly liked and they are probably more prone to failure in extreme temperatures but I've never before heard of a case when they are taken out of use as a precaution in the relatively modest temperatures we've had in the last few days. So I ask again what's so bad about these ones here?

 

[chiltern trev]

I presume this is the double junction about 800m North of Harrow on the Hill station. Where you can switch between the fast and slow lines and both the inbound and outbound so trains can pass both ways whilst changing from fast to slow or vice versa.

So there are 4 switches and 2 switched diamonds all in a confined space and if I recall correctly there is a cant across all 4 lines (or at least seems to be) and this is not a slow crossing when moving from fast to slow (etc) so I think it needs a lot more maintenance than perhaps might be the case.

Updated - just checked on Google maps and there is a cant as the whole junction is on a curve.