Double-Blocking

[Wilts Wanderer]

The approach control into Newport has no obvious reasons for existing. It applies even for trains going straight on into P4 with no change of linespeed - and even if going over the crossover into P3 it's only a 5mph reduction.

It also only started appearing without warning a few months ago - until then getting greens all the way through Newport was possible.

There must be a root cause for that change. Newport isn’t ARS controlled yet is it?

 

[O L Leigh]

NS139

No, WP133 (formerly NS133).

 

[Bald Rick]

No, WP133 (formerly NS133).

If that’s the signal I think it is (signal in rear of 139) then that has 200 metres to the fouling point where the Up Vauxhall joins, so will accommodate a full overlap.

 

[O L Leigh]

139 is on the Down Derby. It’s on the same gantry as 133 but facing the opposite way.

 

[Bald Rick]

Ok now I’m really embarrassed for conflating my Ups and Downs.

However my answer is the same as in post #20, there’s an overlap of approx 80 metres.

 

[O L Leigh]

Ok now I’m really embarrassed for conflating my Ups and Downs.

Don't worry, old friend. It gets us all in the end.

However my answer is the same as in post #20, there’s an overlap of approx 80 metres.

I don't mean to question your wisdom and knowledge, but can that be right...?

Using the highly suspect methodology of less-than-perfect eyesight, educated guesswork and Google Maps* with it's "measure distance" tool, the conflicting point between a train coming off the Up Vauxhall onto the Down Derby to access New Street and a train heading out of town on the Up Derby cannot be more than 50 metres beyond WP/NS133 at the point where the route crosses over the Up Derby. This would surely put it within an 80 metre overlap.

* If using the link, the signal gantry is the heavier-looking structure where Banbury Street passes underneath the railway.

 

[Shwam3]

I don't mean to question your wisdom and knowledge, but can that be right...?

Plans I have show that WP133 has a 103m swinging overlap, meaning it can be directed either towards the Down Vauxhall if a conflicting train is going Up Vauxhall -> Down Derby, or towards the Up & Down Derby for a Up Vauxhall -> Down Coventry conflict.

 

[louis97]

Plans I have show that WP133 has a 103m swinging overlap, meaning it can be directed either towards the Down Vauxhall if a conflicting train is going Up Vauxhall -> Down Derby, or towards the Up & Down Derby for a Up Vauxhall -> Down Coventry conflict.

Second this, was about to say the same thing.

 

[Right Away]

The approach control into Newport has no obvious reasons for existing. It applies even for trains going straight on into P4 with no change of linespeed - and even if going over the crossover into P3 it's only a 5mph reduction.

It also only started appearing without warning a few months ago - until then getting greens all the way through Newport was possible.

There is an ongoing issue with the lamp proving for the banner repeater for NT1368 signal (the platform 3 up direction starting signal) requiring it to be treated as unreliable until such time that it can be rectified. This could take some time as it will require a full isolation of the OLE and scaffolding to attend to it. To reduce the chance of a driver seeing a change of aspect, the signals that give access to platform 3 approaching the platform from the Cardiff direction (NT1070 on the up main and NT1646 on the down main in the reversible direction) have both been temporarily restricted to operate as approach controlled. Unfortunately this means that trains routed into platform 4 are also affected.

 

[Bald Rick]

I don't mean to question your wisdom and knowledge, but can that be right...?

It wasn’t. I was having a bad day yesterday. Others have answered correctly re the swinging overlap - I now remember quite a discussion about it at the time the scheme plan was approved (along with many other issues!)

 

[O L Leigh]

Plans I have show that WP133 has a 103m swinging overlap, meaning it can be directed either towards the Down Vauxhall if a conflicting train is going Up Vauxhall -> Down Derby, or towards the Up & Down Derby for a Up Vauxhall -> Down Coventry conflict.

Thank you, sir. That’s great information.

It wasn’t. I was having a bad day yesterday. Others have answered correctly re the swinging overlap - I now remember quite a discussion about it at the time the scheme plan was approved (along with many other issues!)

Apologies if it brought back any unpleasant memories, but thanks as always for your input.

There is an ongoing issue with the lamp proving for the banner repeater for NT1368 signal (the platform 3 up direction starting signal) requiring it to be treated as unreliable until such time that it can be rectified. This could take some time as it will require a full isolation of the OLE and scaffolding to attend to it. To reduce the chance of a driver seeing a change of aspect, the signals that give access to platform 3 approaching the platform from the Cardiff direction (NT1070 on the up main and NT1646 on the down main in the reversible direction) have both been temporarily restricted to operate as approach controlled. Unfortunately this means that trains routed into platform 4 are also affected.

Thank you for that insight. Does this also explain the current one-at-a-time queuing arrangement for P3 and 4 as I described above?

 

[craigybagel]

There is an ongoing issue with the lamp proving for the banner repeater for NT1368 signal (the platform 3 up direction starting signal) requiring it to be treated as unreliable until such time that it can be rectified. This could take some time as it will require a full isolation of the OLE and scaffolding to attend to it. To reduce the chance of a driver seeing a change of aspect, the signals that give access to platform 3 approaching the platform from the Cardiff direction (NT1070 on the up main and NT1646 on the down main in the reversible direction) have both been temporarily restricted to operate as approach controlled. Unfortunately this means that trains routed into platform 4 are also affected.

Thanks for that - it's good to know there's a reason for it! Fingers crossed they can get that isolation to fix it soon - all those 1 minute delays it causes must be adding up.