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All across the Great Western territory => Across the West => Topic started by: Btline on January 30, 2009, 20:10:23



Title: Where does the slack come from?
Post by: Btline on January 30, 2009, 20:10:23
Many FGW journeys have increased in length over the years.

On routes such as the Cotswold, it is because of single track.

But why have journeys to Bristol and Plymouth increased? Where is the slack put (apart from before the final stop)?

When Reading is finished, will that alter slack?


Title: Re: Where does the slack come from?
Post by: devon_metro on January 30, 2009, 20:39:42
There's little slack as far as Reading. There is slack between Reading and Swindon, chippenham and bath and bath and Bristol. There is slack between tiverton and exeter on sw services.


Title: Re: Where does the slack come from?
Post by: Zoe on January 30, 2009, 20:45:08
There is slack between tiverton and exeter on sw services.
Some services also appear to have a bit of slack between Reading and Taunton, I have been on a train before now that has done London to Taunton in 1 hour 40 minutes and then had to wait a for a bit at Taunton.


Title: Re: Where does the slack come from?
Post by: inspector_blakey on January 30, 2009, 21:28:20
DID-SWI usually timed at 19 - 20 minutes. A healthy HST can (and often does) make it in about 15.


Title: Re: Where does the slack come from?
Post by: Btline on January 30, 2009, 21:31:10
So why is the slack there?

Is it really needed?


Title: Re: Where does the slack come from?
Post by: Zoe on January 30, 2009, 21:39:29
So why is the slack there?

Is it really needed?
So the trains can be delayed by a bit and still arrive on time?


Title: Re: Where does the slack come from?
Post by: devon_metro on January 30, 2009, 21:50:36
So why is the slack there?

Is it really needed?

Less money in delay minutes. Don't expect any changes with franchise finances tight. When the hsts get a mini buffet and the buffet car us lost on Bristol runs it may mean a few minutes are shave off the times.


Title: Re: Where does the slack come from?
Post by: bemmy on February 01, 2009, 11:50:24
It's about newspaper headlines -- the government's obsession with statistics is to do with appeasing the press, not the needs of passengers. It's exactly the same principle as the school league tables, which do nothing to drive up standards for the majority of pupils.

So, it's better to have a train timetabled to take 1:45 from London to Bristol that arrives on time less than 10 minutes late 90% of the time, than one timetabled to take 1:35 that arrives less than 10 minutes late 80% of the time.

In practice, most trains from London that I've been on get delayed before or at Reading, and make up the time by Swindon or Chippenham. So in theory, after the Reading flyover is built, it should be possible to remove some of the slack. However, if the statistical priorities remain the same, they will use this as an opportunity to improve punctuality.

And the system works! We've all seen the headlines about "Record levels of punctuality!", and people who don't use trains don't need to realise that the trains are getting slower every year, and besides, "since records began" means "since 1995 when the railways were half-destroyed".  ;D


Title: Re: Where does the slack come from?
Post by: Electric train on February 01, 2009, 13:23:39
There's little slack as far as Reading.

What!!!! there's loads of slack in the Reading / Paddington locals, in fact its farcical, with trains often sitting in platforms for several minuets because there have arrived so early.


Title: Re: Where does the slack come from?
Post by: devon_metro on February 01, 2009, 13:43:29
There's little slack as far as Reading.

What!!!! there's loads of slack in the Reading / Paddington locals, in fact its farcical, with trains often sitting in platforms for several minuets because there have arrived so early.

I was talking about HSTs


Title: Re: Where does the slack come from?
Post by: willc on February 01, 2009, 19:21:53
But in 1976 BR managed 20 minutes start to stop Paddington-Reading with HSTs, where 25-27 minutes is typical now. I have been on several late-running services from Oxford in recent years which have had their Slough stop dropped to recover some time and made the trip in 20 minutes, though I guess luck played a part too, considering the number of trains out there these days.


Title: Re: Where does the slack come from?
Post by: devon_metro on February 01, 2009, 19:33:33
Following the rail disasters near Paddington speed limits near to the throat are much lower, HSTs are 2+8 instead of 2+7, TPWS/ATP prevents speeding which was common. etc


Title: Re: Where does the slack come from?
Post by: willc on February 01, 2009, 19:43:19
But with good train handling it can be done, just as on the Cotswold Line drivers can make a mockery of the slack timings if they have been delayed earlier their journey - without breaking any speed limits.


Title: Re: Where does the slack come from?
Post by: Btline on February 01, 2009, 20:19:45
So will it take an additional track or two btw Reading and Paddington to remove the slack?

Do trains ever reach 125 mph these days (on that stretch)?


Title: Re: Where does the slack come from?
Post by: IndustryInsider on February 02, 2009, 02:21:18
But in 1976 BR managed 20 minutes start to stop Paddington-Reading with HSTs, where 25-27 minutes is typical now. I have been on several late-running services from Oxford in recent years which have had their Slough stop dropped to recover some time and made the trip in 20 minutes, though I guess luck played a part too, considering the number of trains out there these days.

Will - are these actual stopwatch recorded running times, or 'glance at the watch as you come into the platform' estimates? I would like to see start/stop timings of 20 minutes with the current infrastructure, safety systems and driving standards. 22 minutes is pretty much the minimum I have ever seen with a clear run and an aggressive driving technique.

Even the Railway Performance Society whose members have been recording regularly for over 30 years have only ever recorded best times of 21m 41s (Up) and 20m 46s (Down). http://www.railperf.org.uk/fast/Great_Western-CrossCountry.pdf (http://www.railperf.org.uk/fast/Great_Western-CrossCountry.pdf)

ATP makes such a difference, whereas before a train could hit Reading platform at over 45mph with the brakes in hard and stop, now ATP will apply the emergency brakes if you try anywhere near that speed. That means the train will grind to a halt halfway down the platform, so it is not surprising drivers are much more cautious. The 'freedom' of no ATP, such as on the Cotswold Line, means drivers can push the boundaries a bit further if needed.


And, to Btline, during normal running all non-stop HST's from Paddington-Reading will reach 125mph between Airport Junction and West Drayton and then not have to brake for Reading until Sonning Cutting.


Title: Re: Where does the slack come from?
Post by: willc on February 02, 2009, 08:59:25
Glance at watch maybe, but nearer the 20 mark than 27. I know the role ATP plays, that's why I said luck. I appreciate that where other trains are plays a part, but if you set off with enough of a gap ahead of you you can take some time back here


Title: Re: Where does the slack come from?
Post by: G.Uard on February 02, 2009, 09:52:41
The average back in those palmy days was around 25-26 minutes, although I do remember runs of around 23 minutes. (I used to commute RDG-PAD on a regular basis).  Apparently, drivers were told to 'go like hell' and as (I think I am right in saying), there were no speed limiters fitted, they quite often did.  I have 'timed' speeds of 135 plus between Slough and Maidenhead, but a stop-watch from the carriage window is notoriously inaccurate.  I believe that the distance is 36 miles and 2 chains BTW


Title: Re: Where does the slack come from?
Post by: onthecushions on February 02, 2009, 10:45:27

Some thoughts in the snow:

When HST was introduced (33 years ago!) the official down (Westbound) timings were:

Reading 21.5 minutes, start to pass, 22 minutes stopping. With dwell time about 3 minutes, departure from Reading was 25/26 minutes after leaving Paddington. this was true certainly up to 1988 as I still have the TT. My memories are that this was generally achieved.

The changes since then are:

1. The revised Paddington throat (supposed to accelerate services), which was again revised with lower speeds (40 mph) after the Ladbroke Grove crash. I have the 1991 Railscene cab ride video which shows how much clearer the route seemed before Heathrow Express.

2. The conflict with Heathrow Express, particularly East-bound means frequent signal checks for inbound HST's, adding several minutes, because of poor HST acceleration.

3. Reading's platform 4 used to have a speed limit of 80 mph which has now been reduced to 50 mph. I imagine this means that signalling approach control must now kick in,  i.e. a crawl up to a red signal (RA28), which clears if the train takes long enough but stops the train dead if not. All this adds up to a stranglehold on the main line, slashing capacity, creating queues and blossoming euphemisms from, "waiting for a platform" to the bureaucratically more satisfying, "awaiting platform allocation".

4. Overcrowded HST's take time to empty onto platform 4, lacking 1/3, 2/3 sliding doors and having many un-practised occasional passengers with luggage, who don't shut doors.

5. In compensation, we don't now have 70 mph heritage dmus or 90 mph turbos on the 125 mph main line. The MTU re-engined power cars also seem nippier - does anyone have any figures?

OTC


Title: Re: Where does the slack come from?
Post by: eightf48544 on February 02, 2009, 10:59:58
There is also another problem from Padd to West Drayton and that's the speed of response of the IECC. Unlike Slough and Reading MAS which normally works auto i.e a signal will  change up once a train passess the clearing point of the next signal, thus most of the time the signal will be showing green.

Whereas in the IECC area many signals are held at read until the compter ARS decides to change up.

When I travelled regularly on the 17:36 Bourne End first coach left hand side facing, you could see the signals out of Padd. Sometimes you could pick up a double yellow around Ealing pass a single yellow and then get the next signal at green, which means the train in front was at least 3 sections ahead instead of 1 in auto areas, because the IECC was slow in responding. Which means that the run was knocked out of the train but as it was a Turbo not as badly as an HST with ATP.


Title: Re: Where does the slack come from?
Post by: Boppy on February 02, 2009, 11:41:22
I've commuted between Reading and Paddington for a good while now and in my experience before the Ladbroke Grove incident the trains were timetabled at 24 -26 mins to do the journey (with the train taking 23mins when there were no hold ups) and often did it in that time.

However, these days I expect more like 30mins for the journey due to the reasons in the last few posts - I still think this is a pretty good time but still on occasions the train manages to do Paddington to Reading in 23mins (I never find this is the case going the other way any longer) and it always makes my proud that the train can be this quick and on time! :)  Unfortunately, looking up at the screen at Reading when it does it this quickly I then see it has 5 mins or so of slack at Reading to sit there for!

On another note - big thumbs up to FGW for a v quick service into Paddington from Reading this morning for me in the snow.  Well done!


Title: Re: Where does the slack come from?
Post by: IndustryInsider on February 02, 2009, 14:10:17
There is also another problem from Padd to West Drayton and that's the speed of response of the IECC. Unlike Slough and Reading MAS which normally works auto i.e a signal will  change up once a train passess the clearing point of the next signal, thus most of the time the signal will be showing green.

Whereas in the IECC area many signals are held at read until the compter ARS decides to change up.

When I travelled regularly on the 17:36 Bourne End first coach left hand side facing, you could see the signals out of Padd. Sometimes you could pick up a double yellow around Ealing pass a single yellow and then get the next signal at green, which means the train in front was at least 3 sections ahead instead of 1 in auto areas, because the IECC was slow in responding. Which means that the run was knocked out of the train but as it was a Turbo not as badly as an HST with ATP.

I think that has more to do with the signal spacing and sighting around the Ealing area. If you're following another train close behind the signals are spaced very closely (hence clear quickly) as far as the junction east of Ealing, then get slightly further apart with poor visibility until Southall where the sighting issues are removed by the long straight until nearly as far as Hayes. Net result is that the trains get bunched up a little at Ealing waiting the trains ahead to clear the longer sections, the following train gets a double or single yellow, but by the time the driver has braked appropriately for the poorly sighted signals they have stepped up, and you are then on straight track with the ability to see 2/3 sections ahead on a clear day.


Title: Re: Where does the slack come from?
Post by: Btline on February 02, 2009, 15:02:49
Of course, once Crossrail starts, there will be extra slow, 90 mph max, stoppers to Oxford on the fast lines.

And then consider the Heathrow Hub. All trains will stop there, and will have a large dwell to let passengers with luggage get off.

I predict that scheduled timings will reach 30+ mins after these developments.
 >:(


Title: Re: Where does the slack come from?
Post by: IndustryInsider on February 02, 2009, 21:14:00
Of course, once Crossrail starts, there will be extra slow, 90 mph max, stoppers to Oxford on the fast lines.

I don't think there will be. It simply won't be possible without reducing the HSS service - It's not a case of slowing the fast trains down, there simply isn't the paths for any more trains on the Mains without seriously compromising on the infrastructure. Heathrow Express should, in my opinion, reduce in frequency from every 15 minutes to every 20 minutes as there will be less call for it due to the Crossrail trains heading there from central/east London. That would release one path per hour.

If I can throw my hat in the ring, I fully expect Crossrail to be operating from/to Reading from its inception, and I would bet that the half-hourly Oxford-Paddington stoppers will only run as far as Reading, or possibly divert to Gatwick Airport.


Title: Re: Where does the slack come from?
Post by: willc on February 02, 2009, 22:09:40
Quote
I would bet that the half-hourly Oxford-Paddington stoppers will only run as far as Reading

Which was exactly what they were doing today! But with the added benefit that they mostly seemed to be calling all stations, rather than skipping odd stops which they normally do.


Title: Re: Where does the slack come from?
Post by: IndustryInsider on February 03, 2009, 15:11:03
Quote
I would bet that the half-hourly Oxford-Paddington stoppers will only run as far as Reading

Which was exactly what they were doing today! But with the added benefit that they mostly seemed to be calling all stations, rather than skipping odd stops which they normally do.

Culham and Appleford always seem to see their most frequent service when an emergency timetable is in place!


Title: Re: Where does the slack come from?
Post by: onthecushions on February 03, 2009, 15:53:25
Looking ahead a little, at the risk of extending the OP,  IC electrification, Crossrail and Heathrow Hub (they are now calling the perimeter the "campus"!) will require more track for any sort of service quality.

How might this work?

New IC trains will certainly have a 125mph/200kph+ capability and have a good  business case to use their speed. This means that the main lines have to be special - a French LGV in fact, with closer sleeper spacings, wider separation,  extra signal aspects for each extra 50km/hr above 200 kph, specialised maintenance etc, in short not a mixed traffic and speed railway. This leaves the rest of us in a queue at the speed of the slowest on the relief lines. Now RailTrack did suggest 6 tracks all the way to Reading, a counsel of perfection. Practically, we could have some 6 tracking, or 4-track relief lines  - passing loops in effect, at a number of locations where the formation already exists. We could also use the bays - Platform 5 at Slough etc to terminate stoppers ahead of semi-fasts.

Not perfect but better than sitting at red signals.

OTC


Title: Re: Where does the slack come from?
Post by: Btline on February 03, 2009, 16:01:56
I think 6 tracking is required (with the fast lines capable of 140 mph).

Don't build the Heathrow Hub. The HX and Crossrail will be enough!

Build a spur to have Reading - Heathrow local trains (operated by Crossrail).


Title: Re: Where does the slack come from?
Post by: Zoe on February 03, 2009, 16:15:04
Don't build the Heathrow Hub. The HX and Crossrail will be enough!
I'm not sure that many people will use Crossrail to Heathrow rather than the Piccadilly line as there are still going to be premium fares on the Hayes to Heathrow section.


Title: Re: Where does the slack come from?
Post by: Btline on February 03, 2009, 16:25:34
Don't build the Heathrow Hub. The HX and Crossrail will be enough!
I'm not sure that many people will use Crossrail to Heathrow rather than the Piccadilly line as there are still going to be premium fares on the Hayes to Heathrow section.

I forgot about the Tube - Another reason why not to build the Hub! :D

And if a Waterloo - Terminal 5 - Heathrow Central service gets build, that'll be another reason.

Chiltern were considering a direct line from their route, through Uxbridge to the airport, as well. I doubt this gets built.


Title: Re: Where does the slack come from?
Post by: IndustryInsider on February 03, 2009, 22:04:57
I think 6 tracking is required (with the fast lines capable of 140 mph).

It would be nice. But it ain't gonna happen! You could (and probably will with Crossrail) have 5 tracks between Airport Junction and Iver/Langley. You can even throw in a few passing loops here and there, but to have 6 tracks between Paddington and Reading think of the civil engineering that would be required...

1) Rebuild of ALL stations

2) Widening of 'tunnels' at Ealing

3) Replacement of Wharnecliffe Viaduct and Hanwell Viaduct

4) Replacement of Maidenhead Thames bridge

5) Replacement of countless other bridges

6) Long embankments/cuttings between Taplow and Twyford to be widened

Imagine the cost of that little lot. And I could go on....


More likely/sensible is a dedicated High Speed line following alongside the M4 corridor.


Title: Re: Where does the slack come from?
Post by: willc on February 04, 2009, 00:08:39
Quote
I would bet that the half-hourly Oxford-Paddington stoppers will only run as far as Reading

Which was exactly what they were doing today! But with the added benefit that they mostly seemed to be calling all stations, rather than skipping odd stops which they normally do.

Culham and Appleford always seem to see their most frequent service when an emergency timetable is in place!

And not forgetting Ascott-under-Wychwood, which enjoyed an excellent Saturday service when the Hanborough-Oxford section was shut last month during the relaying of the loops at Oxford.

Quote
Don't build the Heathrow Hub. The HX and Crossrail will be enough!

No they won't and they will be of no use whatever to anyone travelling to or from the airport from further afield, ie most of the Great Western network area. Successful airport stations elsewhere offer both local shuttles and long-distance services, eg Birmingham International, Stansted, Manchester Airport and many more across Europe.

I'm amazed anyone at all uses Heathrow Express, or maybe they're all on expense accounts so don't mind paying ^16.50 one-way, or ^32 return (and you can stick on ^3 more on both if you buy on board). First class is ^26 single and ^50 return.

Connect only takes about 10 minutes longer and costs ^6.90 single or ^13.80 return.


Title: Re: Where does the slack come from?
Post by: Btline on February 04, 2009, 21:41:05
I would say that the Tube and Crossrail will be enough to serve Londerners.

People for the BR network can take the coach to Reading or Watford.

And hopefully they'll build spur lines facing towards Reading.


Title: Re: Where does the slack come from?
Post by: willc on February 04, 2009, 23:36:48
Quote
People for the BR network can take the coach to Reading or Watford.

Have you tried taking the coach to or from Reading in the peaks? It has an extended journey time and the M4 is a bumper to bumper crawl.

If you are going to do the job, then do it properly. In this case, that means providing a station offering long-distance services (which Birmingham International has done for more than 30 years) - there are already lots of ways for Londoners to get to Heathrow and that won't change. How about doing something for everyone else for once? Like all the people living in FGW land.


Title: Re: Where does the slack come from?
Post by: Btline on February 05, 2009, 12:56:32
Fine, build the spur, and enlarge/rebuild Heathrow Central.

Then extend XC services which terminate at Reading in, and selected FGW services.



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