On Sat, 21 Apr 2007 22:17 +0100 (BST), (Colin
Rosenstiel) wrote:

In article ,
(Andy) wrote:

"Movilla" wrote in message
...
wrote in message
ups.com...
It's always been like this since the dot matrix indicators were
installed in the late-80s.

Fair enough. But how do LT work out their minutes?

The story I was told was they were designed to make customers feel
like they are getting a better service as people would not notice
the difference between lu and real time.

At East Putney it's the other way round. The sign says the next train is
due in 3 minutes as the train appears round the corner and enters the
platform.

Hammersmith (Picc westbound) is similar to this. It also annoys me
that it lists the first train, plus the next train to a different
destination. "1. Heathrow 1 min / Next train to Northfields in 5 min"
is not helpful if you're trying to go to Rayners Lane. And in any
case, the next train to Northfields is in 1 min.

James Farrar wrote:
On Sat, 21 Apr 2007 22:17 +0100 (BST), (Colin
Rosenstiel) wrote:

In article ,
(Andy) wrote:

"Movilla" wrote in message
...
wrote in message
ups.com...
It's always been like this since the dot matrix indicators were
installed in the late-80s.

Fair enough. But how do LT work out their minutes?

The story I was told was they were designed to make customers feel
like they are getting a better service as people would not notice
the difference between lu and real time.

At East Putney it's the other way round. The sign says the next
train is due in 3 minutes as the train appears round the corner and
enters the platform.

Hammersmith (Picc westbound) is similar to this. It also annoys me
that it lists the first train, plus the next train to a different
destination. "1. Heathrow 1 min / Next train to Northfields in 5 min"
is not helpful if you're trying to go to Rayners Lane. And in any
case, the next train to Northfields is in 1 min.

I think you'll find it says "Next train to XXXXXX *within* 5 min", so it is
actually correct (though not very helpful, as you say).
--
Richard J.
(to email me, swap 'uk' and 'yon' in address)

On Apr 21, 4:34 pm, "Peter Corser"
wrote:
Movilla wrote:
wrote in message
oups.com...
It's always been like this since the dot matrix indicators were
installed in the late-80s.

Fair enough. But how do LT work out their minutes?

Basically they were the estimated time for off peak trains (senior operators
did not like the idea of a train arriving "early").

The original signs (on the Northern Line) were fed from the central control
computer (at Coburg Street) data for each platform. This computer was only
reading states - not actually performing control (political reasons)
functions. I wrote the interface software from the computer to the signs.
When we commissioned a specific sign the guy who wrote the software
interfacing the train running data to my output process calculated the
approach time for a reasonable off peak timing and would then go (or send
someone else) to the appropriate platform (checking that the service was
running fairly well before he left the office) and time trains entering the
platform with those of us at the computer end making hand adjustments to
each sign. This allowed the local run in to be fairly accurate as long as
the approaching train was not held on the approach by a tardy departure by
the previous train. The computer was monitoring the position of trains by
track circuit occupancy. The times generated were usually off peak -
bearing in mind that the average interstation time on LUL tube sections is
less than 2 minutes, any time longer than 2 minutes was subject to the
vagaries of platform dwell time at intermediate stations as well as the
difference in timing due to loading and traction voltage variations which
were than common. The system was designed to blank the time for any train
which overdwelled and only restart the timing when the train moved again.
The system was only passive and was subject coping with signallers changing
train details or destinations to try and get service back on time.
Junctions were only monitored and it was almost coincidental that the run
from Camden Town to Euston was about 2 minutes. If the system was
projecting a train down a particular route it would count down on the Euston
signs until it got to Camden (2 mins shown). If it was held by the
signaller the time would blank and if he let the one from the other platform
go first this would be detected as the train left the platform and displayed
shortly thereafter (usually still as 2 mins). If the destination of the new
train had changed you would get the "CORRECTION" display. I thought (and
still do) that most regular travellers would much prefer to be told the
actual position of the train (e.g. "at TCR") because they would soon get the
hang of working out how long a train would take to arrive - but simple
displays were preferred by the operators.

The stand-alone system developed for most other lines was basically
independant of the signalling system using three trigger points (taken from
the signalling track circuits) which counted down from each timing point
with each timing point recalibrating the count (or holding/blanking, if
required). The train description was taken from whatever system was in use
on the line. This was still subject to the vagaies of train running and
platform dwells.

I can't remember what we did to the Victoria Line Identra System!

As the centralised computers became more of a real control system
(signallers using them for control functions as well as monitoring & info -
Met & Jubilee plus Bakerloo Lines at Baker Street) the signs controls were
updated (Met signs again came from the computer control points). The
Central Line displays were, I think, integrated within the computer system -
eventually full ato operation would be able to give much more accurate
arrival data.

PTI (Positive Train Identification) also had a role to play - this is the
transponder bit you may have been thinking about. This is a system which
identifies each train, its destination, number and crew at transponders
sited at critical points around the lines - it provides positive
identification at fixed points only which the other systems can use as
appropriate.

Fully integrated systems now being intalled should allow a much better (more
accurate) display.
--
Peter & Elizabeth Corser
Leighton Buzzard, UK



I am not sure what the original question was based on. Regardless of
accuracy, the system can only give whole minutes. So if it shows 1
minute when the the train is exactly (based on distance) 1 minute
away, how long should it display 1 minute for? Just for an instant?
Till the train arrives? Or should it display 1 minute for the time
that 1 is the nearest number of minutes, ie from 1 minute 30 seconds
till 30 seconds, after which it displays 0?

In that case it would always display 1 minute from 1 minute 30
seconds. But it should display 2 minutes from 2 minutes 30 seconds to
1 minute 30 seconds. Did the original post imply that 2 minutes is
displayed for longer than this?

Richard J. wrote:

I think you'll find it says "Next train to XXXXXX *within* 5 min", so it is
actually correct (though not very helpful, as you say).

Although personally I prefer the (not excessive) inaccuracy of the
Hammersmith display to the the spurious accuracy of those at many other
stations.

What I would really like to see however is the 'next train' information
displayed outside the stations. There are a a few journeys I make where
the choice between modes of transport or between different tube lines
could be effected by the few minutes difference between the train
arrivals. (Admittedly it would only make a few minutes difference so is
probably not worth a lot of money to me and so not worth TfL actually
doing).


--
Each day a man watched a donkey walk past a high wood fence with one
plank removed. Each day he saw a nose, then the ears, then the neck,
forequarters, back and finally the tail. He pondered this for a time
and eventually declared. “I understand now. The nose causes the tail”

"MIG" wrote in message
ps.com...
On Apr 21, 4:34 pm, "Peter Corser"
wrote:
In that case it would always display 1 minute from 1 minute 30
seconds. But it should display 2 minutes from 2 minutes 30 seconds to
1 minute 30 seconds. Did the original post imply that 2 minutes is
displayed for longer than this?

That's what I meant. For example, the 2 minutes time is displayed for 1 min,
20 seconds. The worse example I've seen of stuck minutes has been on the
Circle line where a minute can be anywhere up to 2 minutes in real time.

Peter's reply explained a lot.

"James Farrar" wrote in message


Hammersmith (Picc westbound) is similar to this. It also annoys me
that it lists the first train, plus the next train to a different
destination. "1. Heathrow 1 min / Next train to Northfields in 5 min"
is not helpful if you're trying to go to Rayners Lane. And in any
case, the next train to Northfields is in 1 min.

I wonder why Hammersmith has this unusual system? As you say, it's less
useful (if pedantically more accurate) than the usual listings of the
next three trains. Was it an experiment that failed, and so wasn't
repeated?

On Sun, 22 Apr 2007 20:32:00 GMT, David Howdon
wrote:

Richard J. wrote:

I think you'll find it says "Next train to XXXXXX *within* 5 min", so it is
actually correct (though not very helpful, as you say).

Although personally I prefer the (not excessive) inaccuracy of the
Hammersmith display to the the spurious accuracy of those at many other
stations.

What I would really like to see however is the 'next train' information
displayed outside the stations. There are a a few journeys I make where
the choice between modes of transport or between different tube lines
could be effected by the few minutes difference between the train
arrivals. (Admittedly it would only make a few minutes difference so is
probably not worth a lot of money to me and so not worth TfL actually
doing).

This is starting to be introduced at station refurbishments, seemingly
as a standard feature from what I can tell.

On Sun, 22 Apr 2007 20:32:00 GMT, David Howdon
wrote:

What I would really like to see however is the 'next train' information
displayed outside the stations. There are a a few journeys I make where
the choice between modes of transport or between different tube lines
could be effected by the few minutes difference between the train
arrivals. (Admittedly it would only make a few minutes difference so is
probably not worth a lot of money to me and so not worth TfL actually
doing).

Definitely agree with this. Since the "new" PIS (since replaced again
as it was awful) was installed in the late 90s, the main underground
Merseyrail stations have a "next train" for all lines displayed by the
entrance to the ticket office. It is most useful in deciding whether
to run or dawdle.

Neil

--
Neil Williams
Put my first name before the at to reply.

On Apr 22, 9:49 pm, "Recliner" wrote:
I wonder why Hammersmith has this unusual system? As you say, it's less
useful (if pedantically more accurate) than the usual listings of the
next three trains. Was it an experiment that failed, and so wasn't
repeated?

Hammersmith is an older signalling site that uses programme machines
to operate the signals and junctions at the station. As a result,
there is no unified information network available like the one between
Earl's Court and Arnos Grove to transmit train timing info - the
displays have to rely on the programme machines to know what the next
train's destination is.

Recliner wrote:
"James Farrar" wrote in message


Hammersmith (Picc westbound) is similar to this. It also annoys me
that it lists the first train, plus the next train to a different
destination. "1. Heathrow 1 min / Next train to Northfields in 5 min"
is not helpful if you're trying to go to Rayners Lane. And in any
case, the next train to Northfields is in 1 min.

I wonder why Hammersmith has this unusual system? As you say, it's
less useful (if pedantically more accurate) than the usual listings
of the next three trains. Was it an experiment that failed, and so
wasn't repeated?

In the case descibed the system fails to be useful, but if you have three
trains to Heathrow followed by a Rayners train, the Hammersmith system is
certainly more useful than LU's idiotic standard of showing the next three
trains, or worse, showing the next two trains soldly and the third and
fourth trains alternately. LU seem incapable of asking themselves "What do
passengers want to know?" and providing it.