Interlaced track near Mitcham - what's the point?

[Purple Train]

On the Tramlink system, in the Mitcham area, there's a section of interlaced track. Wikipedia said that it was included as the cutting towards Belgrave Walk was too narrow, but, if that was the only consideration, why not just use plain single track? Was it simply to avoid building points at each end, or is there another reason?
(Or, indeed, no reason at all?)

(Photograph courtesy of Wikipedia)

 

[hexagon789]

On the Tramlink system, in the Mitcham area, there's a section of interlaced track. Wikipedia said that it was included as the cutting towards Belgrave Walk was too narrow, but, if that was the only consideration, why not just use plain single track? Was it simply to avoid building points at each end, or is there another reason?
(Or, indeed, no reason at all?)
View attachment 117902
(Photograph courtesy of Wikipedia)

Clearance issues I understand

 

[steamybrian]

Avoids the maintenance of points

 

[paul1609]

For a tramway where the trams are driven on line of sight it a simpler and safer system of operation in that you don't have any point operating mechanisms to go wrong.

 

[Snow1964]

The cutting was too narrow as an unstable part had years previously had retaining wall added that imposed on alignment of a potential second track. Could have been widened (at a cost) but the tram conversion budget meant wasn’t worth it for short length

The short interlaced section avoids installing points so keeps it simple

 

[geoffk]

I assume BR didn't adopt a similar policy through the Hastings line tunnels because of possible issues with the live rail.

 

[Recessio]

I assume BR didn't adopt a similar policy through the Hastings line tunnels because of possible issues with the live rail.

Edit: previous post deleted, I misunderstood the quoted post.

How does live rail work with interlaced track? Presumably the interlacing is spaced so you don't have a live rail where you need a running rail to be?

 

[Basil Jet]

I assume BR didn't adopt a similar policy through the Hastings line tunnels because of possible issues with the live rail.

A pair of live rails, one each side, might do the trick. At Hastings, I wonder if the need to narrow the twin track was so slight that they might have got away with 5 rails (two tracks and a shared live rail between them, obviously signalled as a single line), but they would need special sleepers made, so just didn't bother.

 

[Taunton]

Interlaced track, avoiding points, is quite common on tramways. Here in Leidsestraat, Amsterdam, a single track busy but narrow street, with passing loops every few hundred metres at each canal bridge, the whole street is done closely interlaced, avoiding a series of points :

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I don't think Network Rail has any interlaced track, so no experience.

 

[edwin_m]

Interlaced track, avoiding points, is quite common on tramways. Here in Leidsestraat, Amsterdam, a single track busy but narrow street, with passing loops every few hundred metres at each canal bridge, the whole street is done closely interlaced, avoiding a series of points :

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I don't think Network Rail has any interlaced track, so no experience.

Interlaced track may also be used to avoid putting a point in the middle of a road junction, as at Croydon and Nottingham.

 

[Basil Jet]

Interlaced track may also be used to avoid putting a point in the middle of a road junction, as at Croydon and Nottingham.

In Amsterdam there is (was?) at least one place where the points are three tram lengths of interlaced track before the junction: this is so that trams can trickle through the points over time and queue on the correct track, so that when the lights turn green all three trams whizz off in different directions without wasting any green time on changing points.

 

[tbtc]

Interlaced track may also be used to avoid putting a point in the middle of a road junction, as at Croydon and Nottingham.

My understanding is that this is the reason for similar short bit of track between the Hillsborough tram stop and the Malin Bridge/ Middlewood junction on Sheffield Supertram

The points are at the north western end of the platform (outside the Rawson Spring pub, https://goo.gl/maps/UriPqx3rsqj6aaor7 ) so that trams are already on the appropriate line when they leave the segregated section and rejoin the traffic of Langsett Road

So the mechanics happen on a bit of track that doesn’t have dozens of buses/ trucks etc lumbering over it (potentially damaging things) and that the points can be repaired without having to close the road

(I love these kind of solutions to problems)

 

[D365]

My understanding is that this is the reason for similar short bit of track between the Hillsborough tram stop and the Malin Bridge/ Middlewood junction on Sheffield Supertram

The points are at the north western end of the platform (outside the Rawson Spring pub, https://goo.gl/maps/UriPqx3rsqj6aaor7 ) so that trams are already on the appropriate line when they leave the segregated section and rejoin the traffic of Langsett Road

So the mechanics happen on a bit of track that doesn’t have dozens of buses/ trucks etc lumbering over it (potentially damaging things) and that the points can be repaired without having to close the road

(I love these kind of solutions to problems)

On the flip side, there are some crossovers which are located on road sections. But I imagine that these crossovers were avoidable, and are infrequently used.

 

[edwin_m]

On the flip side, there are some crossovers which are located on road sections. But I imagine that these crossovers were avoidable, and are infrequently used.

They are presumably also trailing crossovers, so not motorised or detected and either trailed through sprung or worked manually with a lever. So much less to go wrong with these.

To return to the original topic "Interlaced track near Mitcham - what's the point?" - surely the point is that there isn't a point?

 

[Purple Train]

They are presumably also trailing crossovers, so not motorised or detected and either trailed through sprung or worked manually with a lever. So much less to go wrong with these.

To return to the original topic "Interlaced track near Mitcham - what's the point?" - surely the point is that there isn't a point?

Interlaced track may also be used to avoid putting a point in the middle of a road junction, as at Croydon and Nottingham.

Just so that I can work out what you're saying here, are you referring to points in the middle of road junctions at Croydon and Nottingham, or interlaced track laid specifically to avoid putting a point in the middle of a road junction?

 

[edwin_m]

Just so that I can work out what you're saying here, are you referring to points in the middle of road junctions at Croydon and Nottingham, or interlaced track laid specifically to avoid putting a point in the middle of a road junction?

Both Croydon and Nottingham have sections of interlaced track which are for the purpose of avoiding having a motorised point in the middle of a junction.

 

[Purple Train]

Both Croydon and Nottingham have sections of interlaced track which are for the purpose of avoiding having a motorised point in the middle of a junction.

Thank you. Where's the Nottingham example? (I never noticed it - but if it's on a section I travelled on rarely then I might feel a little better about my memory)

 

[edwin_m]

Thank you. Where's the Nottingham example? (I never noticed it - but if it's on a section I travelled on rarely then I might feel a little better about my memory)

Just north of the Forest.

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[Purple Train]

Just north of the Forest.

Ah. In that case I cannot feel any better about my memory - I used to travel on that section most regularly out of all the sections

 

[HSTEd]

How long a distance does interlaced track have to be before two point machines would be considered to have a lower life cycle cost?

Is this impacted by the complexity of the signalling arrangements? What about a hypothetical branch where all the trains are using ETCS L3H and have no need for axle counters and the like?

 

[Basil Jet]

Is this impacted by the complexity of the signalling arrangements?

Why would the signalling for an interlaced track be any different to the signalling for a single track?

 

[Bletchleyite]

Why would the signalling for an interlaced track be any different to the signalling for a single track?

Other than that you need to consider two track circuits, it isn't.

 

[dosxuk]

My understanding is that this is the reason for similar short bit of track between the Hillsborough tram stop and the Malin Bridge/ Middlewood junction on Sheffield Supertram

The points are at the north western end of the platform (outside the Rawson Spring pub, https://goo.gl/maps/UriPqx3rsqj6aaor7 ) so that trams are already on the appropriate line when they leave the segregated section and rejoin the traffic of Langsett Road

So the mechanics happen on a bit of track that doesn’t have dozens of buses/ trucks etc lumbering over it (potentially damaging things) and that the points can be repaired without having to close the road

(I love these kind of solutions to problems)

I believe that is also the case with this (very short) bit of interlaced track at the Cathedral crossover - without the interlacing the point motors would have been in the middle of the York Street crossing.

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[HSTEd]

Why would the signalling for an interlaced track be any different to the signalling for a single track?

No point machines, and all the equipment required to prove them.
If you can use ETCS 3H you don't need any power supplies at those locations at all.

 

[pdeaves]

Other than that you need to consider two track circuits, it isn't.

Fundamentally, it could even be one track circuit with pair of rails bonded together. However, I doubt it would be done so simply!

 

[edwin_m]

The signalling for non-interlaced track would have to operate and detect the points - even if it was of a form that didn't need other trackside equipment.

 

[MCR247]

Ah. In that case I cannot feel any better about my memory - I used to travel on that section most regularly out of all the sections

One of the tracks that is interlaced is rarely used - it is the access to/from the middle platform at the Forest from the Wilkinson St direction. The other is the normal southbound line into the southbound platform

 

[Revaulx]

Both Croydon and Nottingham have sections of interlaced track which are for the purpose of avoiding having a motorised point in the middle of a junction.

Manchester also: the up track that splits into two at the foot of the ramp coming down from Deansgate-Castlefield.

 

[Lucan]

The site of the Mitcham interlacing had double track originally - from around 1802 (not a typo!). The Surrey Iron Railway came through here, although it had a level crossing with the London Road rather than going under it. The LBSC seems to have dug deeper and built the road over-bridge when they bought the SIR trackbed for their Croydon-Wimbledon branch.

The LBSC/SR/BR branch was mostly single track but was double for the mile from Mitcham Junction, through Mitcham Station, to Mitcham goods yard, the site of which was in the background of the top photo. This stretch was also the passing loop for the two shuttle passenger trains that worked the branch.

Around 1970 the wall on the right of the photo started subsiding. It belongs to the back garden of a large house on London Road that at the time was the Mitcham Labour CLub and is now some sort of church. The wall was first braced with timbers with footings in the "Up" track (the Croydon direction). The line was singled from a point on the Up side of Mitcham Station and the Up platform fell out of use. The goods yard was closed about that time. Later, the up track was lifted and the timbers were replaced by the massive concrete masonry seen in the photo today.

 

[Purple Train]

One of the tracks that is interlaced is rarely used - it is the access to/from the middle platform at the Forest from the Wilkinson St direction. The other is the normal southbound line into the southbound platform

That doesn't make my memory feel at all better, as I'm now going, "What middle platform?"