DLR trains too speedy so engineers slow them down

[Recliner]

Speed restrictions have been introduced on the automated Docklands Light
Railway (DLR), after engineers discovered the trains were going too fast on
some sections of track.

The speed limits were brought in after Transport for London (Tfl) engineers
found there wasn't enough of a safety margin between the speed of the
trains and the maximum recommended speed.
It was discovered during a review of the signalling system.

Most sections have been slowed by 5kmph, TfL said, adding that the trains
never went over the recommended track speed.

https://www.bbc.co.uk/news/articles/c4gqgg9q2dro

[M***@dastardlyhq.com]

On Mon, 16 Sep 2024 20:28:59 GMT

Post by Recliner
Speed restrictions have been introduced on the automated Docklands Light
Railway (DLR), after engineers discovered the trains were going too fast on
some sections of track.
The speed limits were brought in after Transport for London (Tfl) engineers
found there wasn't enough of a safety margin between the speed of the
trains and the maximum recommended speed.
It was discovered during a review of the signalling system.
Most sections have been slowed by 5kmph, TfL said, adding that the trains
never went over the recommended track speed.

Their reasoning doesn't make any sense - they can't be going too fast yet not
speeding at the same time. Possibly they meant too fast given the gap to the
train in front but thats not what the article is saying.

[Recliner]

Post by M***@dastardlyhq.com
On Mon, 16 Sep 2024 20:28:59 GMT

Post by Recliner
Speed restrictions have been introduced on the automated Docklands Light
Railway (DLR), after engineers discovered the trains were going too fast on
some sections of track.
The speed limits were brought in after Transport for London (Tfl) engineers
found there wasn't enough of a safety margin between the speed of the
trains and the maximum recommended speed.
It was discovered during a review of the signalling system.
Most sections have been slowed by 5kmph, TfL said, adding that the trains
never went over the recommended track speed.

Their reasoning doesn't make any sense - they can't be going too fast yet not
speeding at the same time. Possibly they meant too fast given the gap to the
train in front but thats not what the article is saying.

They’re intended to run at below the local maximum allowed speed, but have
been getting too close to it. There’s supposed to be a larger margin than
there has been, so they’re slowing them down to maintain the planned
margin. In other words, just like driven trains, they are supposed to
cruise at below their maximum allowed speeds, and were getting too close.

[M***@dastardlyhq.com]

On Tue, 17 Sep 2024 10:56:12 GMT

Post by M***@dastardlyhq.com
Their reasoning doesn't make any sense - they can't be going too fast yet not
speeding at the same time. Possibly they meant too fast given the gap to the
train in front but thats not what the article is saying.

They’re intended to run at below the local maximum allowed speed, but have
been getting too close to it. There’s supposed to be a larger margin than
there has been, so they’re slowing them down to maintain the planned
margin. In other words, just like driven trains, they are supposed to
cruise at below their maximum allowed speeds, and were getting too close.

In that case either there's a bug in the train control software that has
only just been triggered or someone has been fiddling with the configuration
because train performance is monitored and recorded in detail and they
would/should have noticed this long ago otherwise.

[Recliner]

Post by M***@dastardlyhq.com
On Tue, 17 Sep 2024 10:56:12 GMT

Post by Recliner

Post by M***@dastardlyhq.com
Their reasoning doesn't make any sense - they can't be going too fast yet not
speeding at the same time. Possibly they meant too fast given the gap to the
train in front but thats not what the article is saying.

They’re intended to run at below the local maximum allowed speed, but have
been getting too close to it. There’s supposed to be a larger margin than
there has been, so they’re slowing them down to maintain the planned
margin. In other words, just like driven trains, they are supposed to
cruise at below their maximum allowed speeds, and were getting too close.

In that case either there's a bug in the train control software that has
only just been triggered or someone has been fiddling with the configuration
because train performance is monitored and recorded in detail and they
would/should have noticed this long ago otherwise.

Yes, it’s odd that this has only just been noticed, presumably while
they’re adjusting the signalling for the new trains. I know there was a
reported problem with their brakes, which weren’t as effective as on the
old trains, and perhaps that led them to study the speed profiles of the
old trains in more detail.

Being cynical, I also wonder if they’re struggling to get the new trains to
match the performance of the old trains, and rather than admit to the
problem, are simply slowing down the old trains to match the best that the
new ones can achieve?

[M***@dastardlyhq.com]

On Tue, 17 Sep 2024 11:22:11 GMT

Post by M***@dastardlyhq.com
In that case either there's a bug in the train control software that has
only just been triggered or someone has been fiddling with the configuration
because train performance is monitored and recorded in detail and they
would/should have noticed this long ago otherwise.

Yes, it’s odd that this has only just been noticed, presumably while
they’re adjusting the signalling for the new trains. I know there was a
reported problem with their brakes, which weren’t as effective as on the
old trains, and perhaps that led them to study the speed profiles of the
old trains in more detail.

You have to wonder how hard it can be to make brakes work properly especially
given the new stock has more wheels per car.

Being cynical, I also wonder if they’re struggling to get the new trains to
match the performance of the old trains, and rather than admit to the
problem, are simply slowing down the old trains to match the best that the
new ones can achieve?

Could be. I suspect the real litmus test will be the long climb out of Bank.

[Recliner]

Post by M***@dastardlyhq.com
On Tue, 17 Sep 2024 11:22:11 GMT

Post by Recliner

Post by M***@dastardlyhq.com
In that case either there's a bug in the train control software that has
only just been triggered or someone has been fiddling with the configuration
because train performance is monitored and recorded in detail and they
would/should have noticed this long ago otherwise.

Yes, it’s odd that this has only just been noticed, presumably while
they’re adjusting the signalling for the new trains. I know there was a
reported problem with their brakes, which weren’t as effective as on the
old trains, and perhaps that led them to study the speed profiles of the
old trains in more detail.

You have to wonder how hard it can be to make brakes work properly especially
given the new stock has more wheels per car.

Presumably the brakes were designed for lower retardation? What may be embarrassing is that maybe the DLR didn't
specify what retardation was required, so CAF might have fulfilled its technical requirements, while producing a train
that needs to be braked earlier, thus reducing the average speeds.

Post by M***@dastardlyhq.com

Post by Recliner
Being cynical, I also wonder if they’re struggling to get the new trains to
match the performance of the old trains, and rather than admit to the
problem, are simply slowing down the old trains to match the best that the
new ones can achieve?

Could be. I suspect the real litmus test will be the long climb out of Bank.

Why would that test the brakes?

[M***@dastardlyhq.com]

On Tue, 17 Sep 2024 14:47:37 +0100

Post by Recliner

Post by M***@dastardlyhq.com
You have to wonder how hard it can be to make brakes work properly especially
given the new stock has more wheels per car.

Presumably the brakes were designed for lower retardation? What may be
embarrassing is that maybe the DLR didn't
specify what retardation was required, so CAF might have fulfilled its
technical requirements, while producing a train
that needs to be braked earlier, thus reducing the average speeds.

You'd expect that kind of stuff to be found out on the test track but
nothing surprises me these days.

Post by Recliner

Post by M***@dastardlyhq.com

Being cynical, I also wonder if they’re struggling to get the new trains to
match the performance of the old trains, and rather than admit to the
problem, are simply slowing down the old trains to match the best that the
new ones can achieve?

Could be. I suspect the real litmus test will be the long climb out of Bank.

Why would that test the brakes?

Matching performance includes acceleration and climbing ability. But the
brakes will certainly be tested in the other direction.

[Recliner]

Post by M***@dastardlyhq.com
On Tue, 17 Sep 2024 14:47:37 +0100

Post by Recliner

Post by M***@dastardlyhq.com
You have to wonder how hard it can be to make brakes work properly especially
given the new stock has more wheels per car.

Presumably the brakes were designed for lower retardation? What may be
embarrassing is that maybe the DLR didn't
specify what retardation was required, so CAF might have fulfilled its
technical requirements, while producing a train
that needs to be braked earlier, thus reducing the average speeds.

You'd expect that kind of stuff to be found out on the test track but
nothing surprises me these days.

Post by Recliner

Post by M***@dastardlyhq.com

Post by Recliner
Being cynical, I also wonder if they’re struggling to get the new trains to
match the performance of the old trains, and rather than admit to the
problem, are simply slowing down the old trains to match the best that the
new ones can achieve?

Could be. I suspect the real litmus test will be the long climb out of Bank.

Why would that test the brakes?

Matching performance includes acceleration and climbing ability. But the
brakes will certainly be tested in the other direction.

I assume they have regeneration, so there may not be much stress on the
brakes going down to the tunnel.