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Journey by Journey => Plymouth and Cornwall => Topic started by: grahame on August 14, 2022, 08:57:50 pm



Title: Tamar Valley line - truncation of services due to lack of working train
Post by: grahame on August 14, 2022, 08:57:50 pm
Quote
Alterations to services between Plymouth and Gunnislake

Due to a broken down train between Plymouth and Gunnislake the line is closed.
Train services running to and from these stations will be suspended. Disruption is expected until the end of the day.

Customer Advice
---------------------------------------------------------------------------------------------
The train used on the Gunnislake branch line has multiple faults, which an engineer has attempted to fix. We are working to find an alternative train that can be used on the line, but the following trains are cancelled until further notice:

17:44 Plymouth to Gunnislake
18:35 Gunnislake to Plymouth
20:01 Plymouth to Gunnislake
20:52 Gunnislake to Plymouth
---------------------------------------------------------------------------------------------
We are sorry for the disruption this might cause to your journey today.
---------------------------------------------------------------------------------------------
Replacement road transport services are conveying passengers between Plymouth and Gunnislake in both directions until further notice. The road transport will depart from the following locations:

Plymouth: Front of the station.
Devonport: Albert Road bus stops, adjacent to Exmouth Road.
Dockyard: Bus stops on Keyham Road (B3396) near the turning to Keat Street.
Keyham: Bus stops on Saltash Road, next to HMS Drake Barracks.
St Budeaux Victoria Road: Bus stops on Wolseley Road, by the bank (towards Plymouth) or by the supermarket (towards Gunnislake).
Bere Ferrers: Station Road nus stop near the Community notice board and post box.
Bere Alston: Car park at the front of the station.
Calstock: Bus stop at the entrance to the station approach road (Lang Gardens).
Gunnislake: Station car park.

Further Information
An update will follow within the next 2 hours.
If you hold a valid single, return, or weekly ticket, you will be able to claim compensation for delays of 15 minutes or more. Please keep your ticket and visit GWR.com/DelayRepay
Last Updated:14/08/2022 19:23

That reads to me as if this continues into tomorrow ... and I wonder about the day after.   Are GWR really that short of working trains or people to drive one over from another depot if there isn't a working one in Plymouth?


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: bobm on August 14, 2022, 10:38:17 pm
Not very well worded I agree but if you think about it if the disruption was going to continue past today why would you only cancel afternoon trains due to lack of a unit?

In any event the trains quoted are Sunday times so could not apply to weekdays.


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: bobm on August 15, 2022, 09:18:15 am
Normal service today - except the on board toilet isn't working.


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: TaplowGreen on August 15, 2022, 10:34:43 am
Normal service today - except the on board toilet isn't working.

Seems to be Exmouth - Paignton which is virtually wiped out today.


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: IndustryInsider on August 15, 2022, 10:45:43 am
Seems to be Exmouth - Paignton which is virtually wiped out today.

Virtually wiped out?  A slight exaggeration.


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: grahame on August 15, 2022, 07:17:13 pm
Seems to be Exmouth - Paignton which is virtually wiped out today.

Virtually wiped out?  A slight exaggeration.

Five round trips wiped off the timetable - out of 35 (there are 7 trains on that circuit, running at 30 minute intervals. So average delay to random passengers is 30 minutes / 7 = 4.5 minutes.  A frequent service can withstand it.

Contrast ...

Just two round trips wiped off the timetable our of 8 (that's just a quarter or one train) on a line like Swindon-Westbury which runs at intervals of about 2 hours and 15 minutes. Average delay to passengers = 34 minutes. So an infrequent service does wipe out practical use at a far lower number of cancellation - if the average holdup for passenger is one half an hour not less that five minutes, that's darned serious -and it's with less than half the cancellations that Exmouth suffered today.

Proof:
1. You can prove anything with statistics
2. Infrequent services to hamlets like Newquay and Melksham should be stepped up to minimise passenger delay.


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: TJ on August 15, 2022, 11:49:00 pm
Wonderful statistics but I live in the real world.

Yes many cancellations will not cause too many problems but when they occur at peak times it is another matter.

GWR's current reliability record leaves much to be desired across the whole of their patch.


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: grahame on August 16, 2022, 02:54:08 am
Wonderful statistics but I live in the real world.

Yeah ... real world micro-example ... 90 minute wait at Trowbridge for a taxi because an infrequent train has been cancelled is far more painful than a 30 minute wait at Exmouth for the next train.

Quote
Yes many cancellations will not cause too many problems but when they occur at peak times it is another matter.

Peak times ARE an issue ... everywhere, and not only on wait times but on capacity on the next service.  A corollary of the issues are that if a train is taken out of service / not available for a whole day, it will inevitably cause cancellations in both peaks as well as during the day.  To some extent that can be mitigated by trying to "pull" a diagram on which the train is running the clock-face service counter-flow during the peak of the peak.  You can see this in practice where  it's the Bristol to Westbury service that is "gapped" in the morning peak if needs must, and not the Westbury to Bristol major morning flow direction.

Quote
GWR's current reliability record leaves much to be desired across the whole of their patch.

Can't disagree with you there as a generality. I can ask whether that's due to GWR's team, First Group direction, DfT direction, general problems of running a business, or unrealistic expectations from us the customers.


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: grahame on August 16, 2022, 04:31:25 am
Wonderful statistics but I live in the real world.

Yeah ... real world micro-example ... 90 minute wait at Trowbridge for a taxi because an infrequent train has been cancelled is far more painful than a 30 minute wait at Exmouth for the next train.


Or this morning at Melksham - single northbound train at 07:53 cancelled, next train 10:02, journey check only offers delay / repay as a "sop".  Still no offer here to use an alternative bus service ...

Quote
Further Information

If you hold a valid single, return, or weekly ticket, you will be able to claim compensation for delays of 15 minutes or more. Please keep your ticket and visit GWR.com/DelayRepay


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: Ralph Ayres on August 17, 2022, 12:23:59 am
Five round trips wiped off the timetable - out of 35 (there are 7 trains on that circuit, running at 30 minute intervals. So average delay to random passengers is 30 minutes / 7 = 4.5 minutes.  A frequent service can withstand it.

Sorry, but I don't think that's a meaningful way of analysing it.  A random passenger has either no delay or a 30 minute one so talking about an average delay is meaningless as no-one is delayed by 4.5 minutes.  As you say, you can prove anything with statistics!


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: grahame on August 17, 2022, 05:19:27 am
Five round trips wiped off the timetable - out of 35 (there are 7 trains on that circuit, running at 30 minute intervals. So average delay to random passengers is 30 minutes / 7 = 4.5 minutes.  A frequent service can withstand it.

Sorry, but I don't think that's a meaningful way of analysing it.

OK - suggest better alternative please.

Quote
A random passenger has either no delay or a 30 minute one so talking about an average delay is meaningless as no-one is delayed by 4.5 minutes.  As you say, you can prove anything with statistics!

Yeah - I should have said "mean" rather than "average".  Definitely the mean - median extra delay if the majority of trains are running is zero.

This is the old "average family has 2.4 children but you'll never find an average family" thing; still (IMHO) a useful measure in terms of overall planning such as number of school spaces.


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: CyclingSid on August 17, 2022, 07:19:17 am
Quote
old "average family has 2.4 children

That is old, as the average family size is nearer 2.4 persons now.


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: grahame on August 17, 2022, 08:29:00 am
Quote
old "average family has 2.4 children

That is old, as the average family size is nearer 2.4 persons now.

Indeed ...

https://blog.ons.gov.uk/2019/08/02/whatever-happened-to-2-point-4-children/

Now perhaps 1.9 children. Many more people live alone these days, and that's a driver behind the need for house building just as population increase and the need for housing stock renewal ...


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: bobm on August 17, 2022, 05:27:08 pm

Just two round trips wiped off the timetable our of 8 (that's just a quarter or one train) on a line like Swindon-Westbury which runs at intervals of about 2 hours and 15 minutes. Average delay to passengers = 34 minutes. So an infrequent service does wipe out practical use at a far lower number of cancellation - if the average holdup for passenger is one half an hour not less that five minutes, that's darned serious -and it's with less than half the cancellations that Exmouth suffered today.


I must admit I am struggling to get my head around this.  If I go to catch a train I aim to be on the platform a minimum of five minutes before it is due to leave.   However I am not actually delayed until the train is late or cancelled.   That applies to everyone aiming to catch that train.  So even if they arrive at the station 20 minutes before me they will be delayed by the same amount of time as I am if the train is late or cancelled.  No one is delayed by a lesser or greater amount - so I don't understand the validity of the 34 minutes.


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: grahame on August 17, 2022, 06:10:55 pm

Just two round trips wiped off the timetable our of 8 (that's just a quarter or one train) on a line like Swindon-Westbury which runs at intervals of about 2 hours and 15 minutes. Average delay to passengers = 34 minutes. So an infrequent service does wipe out practical use at a far lower number of cancellation - if the average holdup for passenger is one half an hour not less that five minutes, that's darned serious -and it's with less than half the cancellations that Exmouth suffered today.


I must admit I am struggling to get my head around this.  If I go to catch a train I aim to be on the platform a minimum of five minutes before it is due to leave.   However I am not actually delayed until the train is late or cancelled.   That applies to everyone aiming to catch that train.  So even if they arrive at the station 20 minutes before me they will be delayed by the same amount of time as I am if the train is late or cancelled.  No one is delayed by a lesser or greater amount - so I don't understand the validity of the 34 minutes.

It's an interesting one ... here is Melksham to Swindon with 2 trains being cancelled and passenger arriving at the station every 10 minutes.  Of course, in reality on such a thin service they would arrange their timing to arrive for a particular train.

Code:
tats = ["05:33","07:21","07:53","10:02","12:33","14:32","16:41","18:50","20:22"]
tata = ["05:33","07:21","07:53","12:33","14:32","16:41","20:22"]

wt = []
for tat in (tats,tata):
peeps = 0
paws = 0
for hour in range(5,20):
for min in range(0,60,10):
popup = hour*60+min
for service in tat:
(h,m) = service.split(":")
goesat = int(h)*60+int(m)
if goesat > popup:
paws += goesat - popup
peeps += 1
break
avw = paws/peeps
print("passengers {} total wait {} minutes - average {:.1f}".format(peeps,paws,avw))
wt.append(avw)
print ("Extra time waited {:.1f} minutes".format(wt[1]-wt[0]))

passengers 90 total wait 5264 minutes - average 58.5
passengers 90 total wait 8331 minutes - average 92.6
Extra time waited 34.1 minutes

change the first two lines to show 1 in 7 services cancelled on a half hourly pattern (5 in the day)

Code:
tats = ["06:05","06:35","07:05","07:35","08:05","08:35","09:05","09:35","10:05","10:35",
"11:05","11:35","12:05","12:35","13:05","13:35","14:05","14:35","15:05","15:35",
"16:05","16:35","17:05","17:35","18:05","18:35","19:05","19:35","20:05","20:35",
"21:05"]
tata = ["06:05","07:05","07:35","08:05","08:35","09:05","09:35","10:35",
"11:05","11:35","12:05","12:35","13:05","14:05","14:35","15:05","15:35",
"16:05","16:35","17:35","18:05","18:35","19:05","19:35","20:05",
"21:05"]

and you get

passengers 90 total wait 1500 minutes - average 16.7
passengers 90 total wait 1860 minutes - average 20.7
Extra time waited 4.0 minutes


Title: Re: Tamar Valley line - truncation of services due to lack of working train
Post by: IndustryInsider on August 17, 2022, 06:17:00 pm
Let it go, Graham!  ;)



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