Delayed trains delaying other trains that are on time

[Busman]

This happens on a frequent basis I've noticed at many stations when waiting for a train. Why should a delayed train from a separate branch (ie, London Victoria) delay a train coming into East Croydon from London Bridge which is on time.

For example, a train from London Victoria is running 6 minutes late to East Croydon at the same time as the on time train from London Bridge. Why should the London Victoria train take priority to delay the London Bridge train - vice versa - surely if a train is already running late, an added 2 minutes won't matter to ensure the on time train gets in on time. This is a bizarre knock on effect I've never really understood.

Can anyone explain?

 

[12LDA28C]

This happens on a frequent basis I've noticed at many stations when waiting for a train. Why should a delayed train from a separate branch (ie, London Victoria) delay a train coming into East Croydon from London Bridge which is on time.

For example, a train from London Victoria is running 6 minutes late to East Croydon at the same time as the on time train from London Bridge. Why should the London Victoria train take priority to delay the London Bridge train - vice versa - surely if a train is already running late, an added 2 minutes won't matter to ensure the on time train gets in on time. This is a bizarre knock on effect I've never really understood.

Can anyone explain?

Perhaps the signallers and controllers are looking at the bigger picture and have visibility of where the delayed train can make up time later in the journey, or where the on-time train can pick up the two minute time loss it might suffer due to being held for the late runner. Trains generally have recovery time built into the schedule. Many other factors will also come into play such as a train or driver's turn round time at destination, next working and so on. It's not as simple as saying 'at location X the delayed train took priority over the on-time train'.

 

[Belperpete]

Consider what would happen if you adopted this method of working at every junction down the line to Brighton. Add on an extra two minutes at East Croydon, then another two minutes at Redhill, then another two minutes at Three Bridges, etc. By the time it finally gets to Brighton it has missed its platform slot.

 

[JonathanH]

For example, a train from London Victoria is running 6 minutes late to East Croydon at the same time as the on time train from London Bridge. Why should the London Victoria train take priority to delay the London Bridge train - vice versa - surely if a train is already running late, an added 2 minutes won't matter to ensure the on time train gets in on time. This is a bizarre knock on effect I've never really understood.

Some passengers rely on connections at East Croydon between trains coming from London Bridge and London Victoria, as their destination isn't served from one or the other. It is best to run trains in timetabled order if possible.

 

[Deepgreen]

It is extremely complex, as it largely depends on what might or could happen further down the line (e.g. if there is any recovery time available for either train, further connections, etc.). Running trains in their correct order is always desirable as long as doing so doesn't cause undue problems. If a six minutes-late train is allowed to proceed ahead of an on-time one, the on-time one my lose two minutes but might be able to recover that further on, or live with two minutes' deficit all the way. However, an eight minutes-late running result for the six minutes-late train may cause knock-on effects that a six minutes deficit might not have. Each train has potentially different time recovery options so it can be very complex, especially at one of the busiest nodes in the UK like East Croydon.

 

[Adrian1980uk]

Of course over a busy section of line, if you further hold up the late running train then you have to slot it in, potentially delaying another train anyway

== Doublepost prevention - post automatically merged: 16 Jun 2024 ==

If you ever tracksy the GEML on a morning between 8 and 9 into Liverpool street, you'll see one after another going in, not many gaps

 

[hick]

The regulation policy in this area is that the right time train has priority (with a few exceptions for trains heading to the Thameslink core).

Running this policy rewards right time presentation and focuses minds on fixing trains that regularly present somewhere late.

Delaying on time trains and then running even a couple of minutes late in to areas such as the Thameslink or ELL cores can start a chain reaction and you can lose hours of good service.

For being able to monitor, control and predict the consequences, it's much better to have one train take more delay than have a dozen trains all with a few minutes in them

 

[Busman]

For being able to monitor, control and predict the consequences, it's much better to have one train take more delay than have a dozen trains all with a few minutes in them

Yes that would be my assumption and makes perfect sense.

 

[The exile]

Yes that would be my assumption and makes perfect sense.

Though there must surely be situations where it doesn’t- the classic being the two track line with a stopper booked out a couple of minutes behind a fast. Fast is 5 late - makes little sense to send the stopper out first about two minutes ahead of the fast which you then delay at each of the 10 stops. Assuming of course, that the stopper doesn’t have a silly turn around at the other end.

 

[Adrian1980uk]

Though there must surely be situations where it doesn’t- the classic being the two track line with a stopper booked out a couple of minutes behind a fast. Fast is 5 late - makes little sense to send the stopper out first about two minutes ahead of the fast which you then delay at each of the 10 stops. Assuming of course, that the stopper doesn’t have a silly turn around at the other end.

That's true but it's not as cut and dry as that, there must be a cut off where you can't hold up the stopper if the fast is 10 min late for example and almost certainly has a queue of stoppers behind it so does it make sense to make everything late or sacrifice the fast to be held up and very late but the stopper on time

 

[Horizon22]

Yes that would be my assumption and makes perfect sense.

Not always. A 5 minute delay on Train A becoming an 8 minute delay on Train A might be worse for the overall service than a 5 minute delay remaining a 5 minute delay or Train A and a 3 minute delay for Train B.

There is a lot to consider including (and not limited to) regulation policy, pathing requirements & dwells, stopping patterns, other conflicts, passenger connections, turnaround time of impacted services, crew arrangements for impacted services etc. This is where proactive controllers will have a good knowledge of what is the best decision at that specific location & time of day.

Reactionary delay can really spiral across half the country in some instances!

 

[The exile]

That's true but it's not as cut and dry as that, there must be a cut off where you can't hold up the stopper if the fast is 10 min late for example and almost certainly has a queue of stoppers behind it so does it make sense to make everything late or sacrifice the fast to be held up and very late but the stopper on time

of course. I was merely providing an example where a hard and fast “punctual train first” might not be the correct approach.

 

[Deepgreen]

Not always. A 5 minute delay on Train A becoming an 8 minute delay on Train A might be worse for the overall service than a 5 minute delay remaining a 5 minute delay or Train A and a 3 minute delay for Train B.

There is a lot to consider including (and not limited to) regulation policy, pathing requirements & dwells, stopping patterns, other conflicts, passenger connections, turnaround time of impacted services, crew arrangements for impacted services etc. This is where proactive controllers will have a good knowledge of what is the best decision at that specific location & time of day.

Reactionary delay can really spiral across half the country in some instances!

Agreed, and pretty much my point from earlier. The OP was talking about down trains, so perhaps less of an issue than up ones, including via the TL core, where the bottleneck is unforgiving. With outbound trains, their turnround times at destination are a factor, but in general, the thinning of trains radiating from London leads to less and less impact on others as they progress. In short, I suppose, experience as well as rules for regulation are vital for controllers and, even then, mistakes can sometimes be made by human beings.

 

[infobleep]

Some passengers rely on connections at East Croydon between trains coming from London Bridge and London Victoria, as their destination isn't served from one or the other. It is best to run trains in timetabled order if possible.

Perhaps this explains why recently a early running Portsmouth Harbour to London Waterloo service was allowed to arrive into Guildford before a Reading service, so delaying it.

The train to London Waterloo was only early due to a load of stops being removed.

It wouldn't usually be a connection but this day it could be for a change, as it was allowed to run in front.

Of course delaying the Reading train might impact people changing at Reading.

There is no simple solution that is the same every time and can be used for every situation.