Trains overtaking each other

edanto

A post on another thread got me thinking.

chipclub wrote:

My major gripe with Irish Rail is the lazy timetabling. Every train stops at every stop. Why not have one that goes non-stop to Drogheda and then Dundalk? You'd cut the journey by about 20 minutes and take a lot of people off the other services running on the same line? There is no thought in their planning.

I've noticed this for years too. One difference between our stations and those I've seen in other countries is that trains rarely, if ever, seem to overtake each other. That may sound odd, but what I mean is that sometimes at English or Australian stations a local train may be pulled in at a station for an extra few minutes while an express train travelling in the same direction overtakes the local train on a third track.

Where I think this need exists particularly is during the morning rush hour. For example, there are huge gaps between the DARTs when the track is being cleared for a suburban to run through. And then it takes a while for the DARTs to reappear, since they're travelling much slower than the suburban was.

Since we don't have third tracks at most of the DART stations - is it possible to use this technique by putting the overtaking train on the other track in the station, or would the risk of an accident be unacceptable?

Basically, are the train management systems reliable enough so that a train could run on the wrong track for a few hundred yards to overtake another one or is that just crazy talk?

There would also be a pretty weird moment for the driver of the second train as he caught up on the parked train, just before he switched tracks.

Calina

edanto wrote:

Since we don't have third tracks at most of the DART stations - is it possible to use this technique by putting the overtaking train on the other track in the station, or would the risk of an accident be unacceptable?

I'd venture to say yes, it would be unacceptable risk.

Ham'nd'egger

The Dublin area tracks are equipped with signalling to allow trains work on the opposite track if required; the term is called "Wrong Way Workiing". The immediate issue with doing it is that trains coming on the opposite direction may need to be held up to allow two track sections to be taken up (It could take up to 10 minutes); but it is possible to implement if needed and has been done.

godtabh

Hamndegger wrote:

The Dublin area tracks are equipped with signalling to allow trains work on the opposite track if required; the term is called "Wrong Way Workiing". The immediate issue with doing it is that trains coming on the opposite direction may need to be held up to allow two track sections to be taken up (It could take up to 10 minutes); but it is possible to implement if needed and has been done.

Isnt that more to do with if its required its there rather than it be a good idea to use it i.e if a train breaks down at a station it doesnt hold up a line as it can be over taken?

Ham'nd'egger

kearnsr wrote:

Isnt that more to do with if its required its there rather than it be a good idea to use it i.e if a train breaks down at a station it doesnt hold up a line as it can be over taken?

It is primarily for that, yes, in case of delays or emergencies. It isn't used as an general overtaking tactic as it requires a lot of line (and time possession).

John R

edanto wrote:

A post on another thread got me thinking.



I've noticed this for years too. One difference between our stations and those I've seen in other countries is that trains rarely, if ever, seem to overtake each other. That may sound odd, but what I mean is that sometimes at English or Australian stations a local train may be pulled in at a station for an extra few minutes while an express train travelling in the same direction overtakes the local train on a third track.

In most cases what you are seeing there is a system with multiple running lines rather than station loops for passing.

Many of the main lines in the UK have four or more lines to seperate express and stopping traffic.

There are some stations with loops for allowing non-stop trains pass stoppers but not that many, in these cases the platform line is normally the loop allowing the through line stay at full line speed.

edanto wrote:

Where I think this need exists particularly is during the morning rush hour. For example, there are huge gaps between the DARTs when the track is being cleared for a suburban to run through. And then it takes a while for the DARTs to reappear, since they're travelling much slower than the suburban was.

Since we don't have third tracks at most of the DART stations - is it possible to use this technique by putting the overtaking train on the other track in the station, or would the risk of an accident be unacceptable?

There would be no significant risk of an accident because before this could be done it would have to be properly signalled and that is where the idea pretty much comes apart.

Having said that, any movement that causes line conflicts does increase the chances of a collision.

edanto wrote:

Basically, are the train management systems reliable enough so that a train could run on the wrong track for a few hundred yards to overtake another one or is that just crazy talk?

It is not about reliability it is about the way trains are controlled to ensure safe operation. For a train to run at speed there needs to be a large distance of free track cleared in front of it. For the train to switch tracks the opposite line without having to slow down that other line would have to be cleared several minutes beforehand.

You would also need high speed points at each end of the station (the sort of points on most IE lines for emergency and shunting are slow speed 20-30mph max) and to allow the stopping train clearance to stop the points would have to be a good distance beyond the station.

Technically it would be possible but in reality to use it as a regular pattern on already busy lines would not work.

edanto wrote:

There would also be a pretty weird moment for the driver of the second train as he caught up on the parked train, just before he switched tracks.

There wouldn't, in that situation the driver would be driving under a proceed signal which would have notified him of the change of line.


This is an idea that people that don't understand how railways work often ask because at first glance it seems like a solution.

The reality is that, particularly for the Northern line out of Connolly the only real solution is to add another running line. Fast trains and stoppers on the same line is a bad mix and to improve speed, frequency and reliability they need to be seperated. passing loops can be useful but unless the timings are very exact it leads to local trains sitting around waiting for expresses to pass or expresses catching up too soon and having to slow down anyway.