Roland Perry <roland@perry.co.uk> wrote:
> In message <sv2tdf$a5n$1@dont-email.me>, at 14:53:35 on Tue, 22 Feb
> 2022, martin.coffee@round-midnight.org.uk remarked:
>> On 22/02/2022 14:29, Roland Perry wrote:
>>> In message <sv2qam$iiq$1@dont-email.me>, at 14:00:54 on Tue, 22 Feb
>>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>>> On 22/02/2022 13:30, Recliner wrote:
>>>>> On Tue, 22 Feb 2022 13:25:27 +0000,
>>>>> martin.coffee@round-midnight.org.uk wrote:
>>>>>
>>>>>> On 22/02/2022 13:13, Roland Perry wrote:
>>>>>>> In message <sv2m9u$lih$1@dont-email.me>, at 12:52:14 on Tue, 22 Feb
>>>>>>> 2022, Certes <none@nowhere.net> remarked:
>>>>>>>> On 22/02/2022 10:59, martin.coffee@round-midnight.org.uk wrote:
>>>>>>>
>>>>>>>>> The  one thing I noticed is that the circumstances are identical to
>>>>>>>>> an  event in Sunningdale about 25 years ago.  The RHTT had not run
>>>>>>>>> and a  train on the Chertsey branch slid onto the main line.
>>>>>>>>> Fortunately no  other train was involved.
>>>>>>>
>>>>>>>>>   The rules should be change to be changed so that normal trains are
>>>>>>>>> banned if the RHTT has not run within the prescribed time.
>>>>>>>>
>>>>>>>> Perhaps they could get away with asking drivers to travel below
>>>>>>>> normal speed limit, as they do in extreme heat or other
>>>>>>>> unhelpful weather conditions, and to be especially cautious
>>>>>>>> approaching junctions even if it results in late running.
>>>>>>>
>>>>>>> Reading between the lines (sorry) I think they are not yet
>>>>>>> convinced the driver was being sufficiently defensive, and are
>>>>>>> looking at why that might be the case.
>>>>>>
>>>>>> What evidence do you have for that statement?
>
>>>>>  I agree with Roland on this. These paras on p14 justify his suggestion:
>>>>>    • Consider the behaviour of both trains during and following
>>>>> the collision and the
>>>>> damage caused to each
>>>>>    • Consider the actions taken on the day of the accident to
>>>>> manage the risk of low
>>>>> adhesion given the time of year and prevailing weather conditions
>>>>>    • Consider the actions of the driver of 1L53 and any factors
>>>>> which may have
>>>>> influenced them
>>>>>    • Consider South Western Railway's policies and processes
>>>>> relating to operating trains in conditions of low wheel/rail
>>>>> adhesion including the dissemination and responses to information
>>>>
>>>> I don't think there is anything in there out of the RAIB's norms. I
>>>> see nothing to support any reading between the the lines.
>
>>> See also:
>>> Train driving
>>> ===========
>>> 37 OTDR data shows that train 1L53 was travelling within the
>>> permitted speed as the train approached Salisbury Tunnel Junction.
>>> RAIB's investigation will continue to consider the driver's actions
>>> and factors that may have influenced them, including the industry's
>>> arrangements for advising drivers about poor adhesion conditions and
>>> the guidance and instructions relating to reporting low adhesion and
>>> driving in such conditions.
>>
>> What's to read between the lines in that?
>
> OK, I was being polite about "reading between the lines", if you think
> they were a bit more explicit than that.

The options seem to be:

- the driver should have been driving more defensively
- the TOC should have done more to warn the driver
- NR should have treated the railhead more assiduously

and all the implications that arise from those three, not mutually
exclusive things.

Sam

--
The entity formerly known as Sam.Wilson@ed.ac.uk
Spit the dummy to reply

Sam Wilson <ukr@dummy.wislons.fastmail.co.uk> wrote:
> Roland Perry <roland@perry.co.uk> wrote:
>> In message <sv2tdf$a5n$1@dont-email.me>, at 14:53:35 on Tue, 22 Feb
>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>> On 22/02/2022 14:29, Roland Perry wrote:
>>>> In message <sv2qam$iiq$1@dont-email.me>, at 14:00:54 on Tue, 22 Feb
>>>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>>>> On 22/02/2022 13:30, Recliner wrote:
>>>>>> On Tue, 22 Feb 2022 13:25:27 +0000,
>>>>>> martin.coffee@round-midnight.org.uk wrote:
>>>>>>
>>>>>>> On 22/02/2022 13:13, Roland Perry wrote:
>>>>>>>> In message <sv2m9u$lih$1@dont-email.me>, at 12:52:14 on Tue, 22 Feb
>>>>>>>> 2022, Certes <none@nowhere.net> remarked:
>>>>>>>>> On 22/02/2022 10:59, martin.coffee@round-midnight.org.uk wrote:
>>>>>>>>
>>>>>>>>>> The  one thing I noticed is that the circumstances are identical to
>>>>>>>>>> an  event in Sunningdale about 25 years ago.  The RHTT had not run
>>>>>>>>>> and a  train on the Chertsey branch slid onto the main line.
>>>>>>>>>> Fortunately no  other train was involved.
>>>>>>>>
>>>>>>>>>>   The rules should be change to be changed so that normal trains are
>>>>>>>>>> banned if the RHTT has not run within the prescribed time.
>>>>>>>>>
>>>>>>>>> Perhaps they could get away with asking drivers to travel below
>>>>>>>>> normal speed limit, as they do in extreme heat or other
>>>>>>>>> unhelpful weather conditions, and to be especially cautious
>>>>>>>>> approaching junctions even if it results in late running.
>>>>>>>>
>>>>>>>> Reading between the lines (sorry) I think they are not yet
>>>>>>>> convinced the driver was being sufficiently defensive, and are
>>>>>>>> looking at why that might be the case.
>>>>>>>
>>>>>>> What evidence do you have for that statement?
>>
>>>>>>  I agree with Roland on this. These paras on p14 justify his suggestion:
>>>>>>    • Consider the behaviour of both trains during and following
>>>>>> the collision and the
>>>>>> damage caused to each
>>>>>>    • Consider the actions taken on the day of the accident to
>>>>>> manage the risk of low
>>>>>> adhesion given the time of year and prevailing weather conditions
>>>>>>    • Consider the actions of the driver of 1L53 and any factors
>>>>>> which may have
>>>>>> influenced them
>>>>>>    • Consider South Western Railway's policies and processes
>>>>>> relating to operating trains in conditions of low wheel/rail
>>>>>> adhesion including the dissemination and responses to information
>>>>>
>>>>> I don't think there is anything in there out of the RAIB's norms. I
>>>>> see nothing to support any reading between the the lines.
>>
>>>> See also:
>>>> Train driving
>>>> ===========
>>>> 37 OTDR data shows that train 1L53 was travelling within the
>>>> permitted speed as the train approached Salisbury Tunnel Junction.
>>>> RAIB's investigation will continue to consider the driver's actions
>>>> and factors that may have influenced them, including the industry's
>>>> arrangements for advising drivers about poor adhesion conditions and
>>>> the guidance and instructions relating to reporting low adhesion and
>>>> driving in such conditions.
>>>
>>> What's to read between the lines in that?
>>
>> OK, I was being polite about "reading between the lines", if you think
>> they were a bit more explicit than that.
>
> The options seem to be:
>
> - the driver should have been driving more defensively
> - the TOC should have done more to warn the driver
> - NR should have treated the railhead more assiduously
>
> and all the implications that arise from those three, not mutually
> exclusive things.
>

Or, of course, fit the trains with DVRS (which isn't even under
consideration for 159s). That would certainly have prevented this crash.

Cutting back more of the post-steam era lineside vegetation would also
help.

On 22/02/2022 23:01, Recliner wrote:
> Sam Wilson <ukr@dummy.wislons.fastmail.co.uk> wrote:
>> Roland Perry <roland@perry.co.uk> wrote:
>>> In message <sv2tdf$a5n$1@dont-email.me>, at 14:53:35 on Tue, 22 Feb
>>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>>> On 22/02/2022 14:29, Roland Perry wrote:
>>>>> In message <sv2qam$iiq$1@dont-email.me>, at 14:00:54 on Tue, 22 Feb
>>>>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>>>>> On 22/02/2022 13:30, Recliner wrote:
>>>>>>> On Tue, 22 Feb 2022 13:25:27 +0000,
>>>>>>> martin.coffee@round-midnight.org.uk wrote:
>>>>>>>
>>>>>>>> On 22/02/2022 13:13, Roland Perry wrote:
>>>>>>>>> In message <sv2m9u$lih$1@dont-email.me>, at 12:52:14 on Tue, 22 Feb
>>>>>>>>> 2022, Certes <none@nowhere.net> remarked:
>>>>>>>>>> On 22/02/2022 10:59, martin.coffee@round-midnight.org.uk wrote:
>>>>>>>>>
>>>>>>>>>>> The  one thing I noticed is that the circumstances are identical to
>>>>>>>>>>> an  event in Sunningdale about 25 years ago.  The RHTT had not run
>>>>>>>>>>> and a  train on the Chertsey branch slid onto the main line.
>>>>>>>>>>> Fortunately no  other train was involved.
>>>>>>>>>
>>>>>>>>>>>   The rules should be change to be changed so that normal trains are
>>>>>>>>>>> banned if the RHTT has not run within the prescribed time.
>>>>>>>>>>
>>>>>>>>>> Perhaps they could get away with asking drivers to travel below
>>>>>>>>>> normal speed limit, as they do in extreme heat or other
>>>>>>>>>> unhelpful weather conditions, and to be especially cautious
>>>>>>>>>> approaching junctions even if it results in late running.
>>>>>>>>>
>>>>>>>>> Reading between the lines (sorry) I think they are not yet
>>>>>>>>> convinced the driver was being sufficiently defensive, and are
>>>>>>>>> looking at why that might be the case.
>>>>>>>>
>>>>>>>> What evidence do you have for that statement?
>>>
>>>>>>>  I agree with Roland on this. These paras on p14 justify his suggestion:
>>>>>>>    • Consider the behaviour of both trains during and following
>>>>>>> the collision and the
>>>>>>> damage caused to each
>>>>>>>    • Consider the actions taken on the day of the accident to
>>>>>>> manage the risk of low
>>>>>>> adhesion given the time of year and prevailing weather conditions
>>>>>>>    • Consider the actions of the driver of 1L53 and any factors
>>>>>>> which may have
>>>>>>> influenced them
>>>>>>>    • Consider South Western Railway's policies and processes
>>>>>>> relating to operating trains in conditions of low wheel/rail
>>>>>>> adhesion including the dissemination and responses to information
>>>>>>
>>>>>> I don't think there is anything in there out of the RAIB's norms. I
>>>>>> see nothing to support any reading between the the lines.
>>>
>>>>> See also:
>>>>> Train driving
>>>>> ===========
>>>>> 37 OTDR data shows that train 1L53 was travelling within the
>>>>> permitted speed as the train approached Salisbury Tunnel Junction.
>>>>> RAIB's investigation will continue to consider the driver's actions
>>>>> and factors that may have influenced them, including the industry's
>>>>> arrangements for advising drivers about poor adhesion conditions and
>>>>> the guidance and instructions relating to reporting low adhesion and
>>>>> driving in such conditions.
>>>>
>>>> What's to read between the lines in that?
>>>
>>> OK, I was being polite about "reading between the lines", if you think
>>> they were a bit more explicit than that.
>>
>> The options seem to be:
>>
>> - the driver should have been driving more defensively
>> - the TOC should have done more to warn the driver
>> - NR should have treated the railhead more assiduously
>>
>> and all the implications that arise from those three, not mutually
>> exclusive things.
>>
>
> Or, of course, fit the trains with DVRS (which isn't even under
> consideration for 159s). That would certainly have prevented this crash.
>
> Cutting back more of the post-steam era lineside vegetation would also
> help.

As usual, it's likely to be a combination of those factors. We have few
accidents because it normally requires multiple failures to cause one.

In message <sv3op0$m95$1@dont-email.me>, at 22:40:32 on Tue, 22 Feb
2022, Sam Wilson <ukr@dummy.wislons.fastmail.co.uk> remarked:
>Roland Perry <roland@perry.co.uk> wrote:
>> In message <sv2tdf$a5n$1@dont-email.me>, at 14:53:35 on Tue, 22 Feb
>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>> On 22/02/2022 14:29, Roland Perry wrote:
>>>> In message <sv2qam$iiq$1@dont-email.me>, at 14:00:54 on Tue, 22 Feb
>>>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>>>> On 22/02/2022 13:30, Recliner wrote:
>>>>>> On Tue, 22 Feb 2022 13:25:27 +0000,
>>>>>> martin.coffee@round-midnight.org.uk wrote:
>>>>>>
>>>>>>> On 22/02/2022 13:13, Roland Perry wrote:
>>>>>>>> In message <sv2m9u$lih$1@dont-email.me>, at 12:52:14 on Tue, 22 Feb
>>>>>>>> 2022, Certes <none@nowhere.net> remarked:
>>>>>>>>> On 22/02/2022 10:59, martin.coffee@round-midnight.org.uk wrote:
>>>>>>>>
>>>>>>>>>> The  one thing I noticed is that the circumstances are identical to
>>>>>>>>>> an  event in Sunningdale about 25 years ago.  The RHTT had not run
>>>>>>>>>> and a  train on the Chertsey branch slid onto the main line.
>>>>>>>>>> Fortunately no  other train was involved.
>>>>>>>>
>>>>>>>>>>   The rules should be change to be changed so that normal
>>>>>>>>>>trains are
>>>>>>>>>> banned if the RHTT has not run within the prescribed time.
>>>>>>>>>
>>>>>>>>> Perhaps they could get away with asking drivers to travel below
>>>>>>>>> normal speed limit, as they do in extreme heat or other
>>>>>>>>> unhelpful weather conditions, and to be especially cautious
>>>>>>>>> approaching junctions even if it results in late running.
>>>>>>>>
>>>>>>>> Reading between the lines (sorry) I think they are not yet
>>>>>>>> convinced the driver was being sufficiently defensive, and are
>>>>>>>> looking at why that might be the case.
>>>>>>>
>>>>>>> What evidence do you have for that statement?
>>
>>>>>>  I agree with Roland on this. These paras on p14 justify his suggestion:
>>>>>>    • Consider the behaviour of both trains during and following
>>>>>> the collision and the
>>>>>> damage caused to each
>>>>>>    • Consider the actions taken on the day of the accident to
>>>>>> manage the risk of low
>>>>>> adhesion given the time of year and prevailing weather conditions
>>>>>>    • Consider the actions of the driver of 1L53 and any factors
>>>>>> which may have
>>>>>> influenced them
>>>>>>    • Consider South Western Railway's policies and processes
>>>>>> relating to operating trains in conditions of low wheel/rail
>>>>>> adhesion including the dissemination and responses to information
>>>>>
>>>>> I don't think there is anything in there out of the RAIB's norms. I
>>>>> see nothing to support any reading between the the lines.
>>
>>>> See also:
>>>> Train driving
>>>> ===========
>>>> 37 OTDR data shows that train 1L53 was travelling within the
>>>> permitted speed as the train approached Salisbury Tunnel Junction.
>>>> RAIB's investigation will continue to consider the driver's actions
>>>> and factors that may have influenced them, including the industry's
>>>> arrangements for advising drivers about poor adhesion conditions and
>>>> the guidance and instructions relating to reporting low adhesion and
>>>> driving in such conditions.
>>>
>>> What's to read between the lines in that?
>>
>> OK, I was being polite about "reading between the lines", if you think
>> they were a bit more explicit than that.
>
>The options seem to be:
>
>- the driver should have been driving more defensively
>- the TOC should have done more to warn the driver
>- NR should have treated the railhead more assiduously

- and perhaps NR should have done more to warn the driver
- and the previous driver to stop at the signal that day might have
better reported the conditions up the chain of command

>and all the implications that arise from those three, not mutually
>exclusive things.

As with many accidents there's a bit of a "Swiss Cheese" (alignment of
holes) flavour, with engineering works etc disrupting normal operations.
I wonder if a nine-car train would have stopped sooner, for example.
--
Roland Perry

On 2022-02-22 10:12:46 +0000, ColinR said:

> On 22/02/2022 00:53, NY wrote:
>> On 21/02/2022 22:08, Recliner wrote:
>>> <martin.coffee@round-midnight.org.uk> wrote:
>>>> https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1055846/IR012022_220221_Salisbury_Tunnel_Junction.pdf
>>>>
>>>>
>>>
>>> Three paras stand out:
>>>
>>> 42 With reference to the RHTT programme, the Wessex route Autumn working
>>> arrangements document stated that ‘Wessex aspire for all routes to be
>>> covered once in 24 hours throughout the Autumn period.’ On weekdays (Monday
>>> to Friday) two RHTT were scheduled to operate over each section of line
>>> each day. The working arrangements document stated that this was ‘to
>>> maximise the chance of each site being treated at least once [every 24
>>> hours]. One set of circuits run at weekends.’
>>>
>>> 43 On the day of the accident (a Sunday), the RHTT that was due to treat
>>> Salisbury Tunnel Junction on the down main line at 17:03 hrs had not yet
>>> passed through the area because it had been rescheduled. This rescheduling
>>> meant that it would (but for the accident) have passed the junction at
>>> around 23:00 hrs. The revised schedule, which was a consequence of planned
>>> engineering work between Southampton and Brockenhurst, meant that there
>>> would have been an interval of 36 hours between the RHTT runs over the
>>> weekend.
>>>
>>> 44 The last RHTT to run over the junction passed over it at 11:06 hrs on 30
>>> October, around 32 hours before the accident occurred. This RHTT delivered
>>> high-pressure water jetting, and although it could apply adhesion modifier
>>> gel, it was not required to do so on this section of track.
>>
>> I presume the period of 24 hours has been found empirically to be the
>> longest that still gives an acceptable level of adhesion if a train
>> uses the track just before RHTT train is due, ie with just under 24
>> hours of grot build-up.
>>
>> Is wheelslide on braking a new phenomenon, or did it also exist with
>> loco-hauled trains (as opposed to multiple units) with their heavier
>> axle loads on the loco's driving/braked wheels. Did tyre brakes on
>> steam locos help to keep the tyres and hence the rails more clear of
>> leaf mulch? Did fewer trees on cuttings in the old days help a lot? Or
>> has it always been a problem?
>
> Yes, there were slipping problems in steam days, not just from leaves.
> Just look at videos of Bullied Pacifics trying to start a heavy train
> out of Waterloo!
> https://www.youtube.com/watch?v=iKzRNrDH5AU
> https://www.youtube.com/watch?v=jWNa2k0PSsM
>
> As Graeme says, speeds were much slower.

That sort of wheel slip is more a feature of the relatively small
number of powered axles (3 axles on quite a heavy train) and the lack
of fine control of torque when starting possible with the basic
controls of a steam locomotive, with the added difficulty that the
torque applied by a steam locomotive is uneven, meaning that even if
the average torque won't slip the wheels, the peaks when ports open and
admit full boiler pressure to the cylinders, will. The issue with
wheel slide on braking is somewhat different, as the brakes apply to
all the axles, not just a few, and the brakign torque is quite smooth
rather than having a force that varies as the wheels rotate.

Robin

Roland Perry <roland@perry.co.uk> wrote:
> In message <sv3op0$m95$1@dont-email.me>, at 22:40:32 on Tue, 22 Feb
> 2022, Sam Wilson <ukr@dummy.wislons.fastmail.co.uk> remarked:
>> Roland Perry <roland@perry.co.uk> wrote:
>>> In message <sv2tdf$a5n$1@dont-email.me>, at 14:53:35 on Tue, 22 Feb
>>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>>> On 22/02/2022 14:29, Roland Perry wrote:
>>>>> In message <sv2qam$iiq$1@dont-email.me>, at 14:00:54 on Tue, 22 Feb
>>>>> 2022, martin.coffee@round-midnight.org.uk remarked:
>>>>>> On 22/02/2022 13:30, Recliner wrote:
>>>>>>> On Tue, 22 Feb 2022 13:25:27 +0000,
>>>>>>> martin.coffee@round-midnight.org.uk wrote:
>>>>>>>
>>>>>>>> On 22/02/2022 13:13, Roland Perry wrote:
>>>>>>>>> In message <sv2m9u$lih$1@dont-email.me>, at 12:52:14 on Tue, 22 Feb
>>>>>>>>> 2022, Certes <none@nowhere.net> remarked:
>>>>>>>>>> On 22/02/2022 10:59, martin.coffee@round-midnight.org.uk wrote:
>>>>>>>>>
>>>>>>>>>>> The  one thing I noticed is that the circumstances are identical to
>>>>>>>>>>> an  event in Sunningdale about 25 years ago.  The RHTT had not run
>>>>>>>>>>> and a  train on the Chertsey branch slid onto the main line.
>>>>>>>>>>> Fortunately no  other train was involved.
>>>>>>>>>
>>>>>>>>>>>   The rules should be change to be changed so that normal
>>>>>>>>>>> trains are
>>>>>>>>>>> banned if the RHTT has not run within the prescribed time.
>>>>>>>>>>
>>>>>>>>>> Perhaps they could get away with asking drivers to travel below
>>>>>>>>>> normal speed limit, as they do in extreme heat or other
>>>>>>>>>> unhelpful weather conditions, and to be especially cautious
>>>>>>>>>> approaching junctions even if it results in late running.
>>>>>>>>>
>>>>>>>>> Reading between the lines (sorry) I think they are not yet
>>>>>>>>> convinced the driver was being sufficiently defensive, and are
>>>>>>>>> looking at why that might be the case.
>>>>>>>>
>>>>>>>> What evidence do you have for that statement?
>>>
>>>>>>>  I agree with Roland on this. These paras on p14 justify his suggestion:
>>>>>>>    • Consider the behaviour of both trains during and following
>>>>>>> the collision and the
>>>>>>> damage caused to each
>>>>>>>    • Consider the actions taken on the day of the accident to
>>>>>>> manage the risk of low
>>>>>>> adhesion given the time of year and prevailing weather conditions
>>>>>>>    • Consider the actions of the driver of 1L53 and any factors
>>>>>>> which may have
>>>>>>> influenced them
>>>>>>>    • Consider South Western Railway's policies and processes
>>>>>>> relating to operating trains in conditions of low wheel/rail
>>>>>>> adhesion including the dissemination and responses to information
>>>>>>
>>>>>> I don't think there is anything in there out of the RAIB's norms. I
>>>>>> see nothing to support any reading between the the lines.
>>>
>>>>> See also:
>>>>> Train driving
>>>>> ===========
>>>>> 37 OTDR data shows that train 1L53 was travelling within the
>>>>> permitted speed as the train approached Salisbury Tunnel Junction.
>>>>> RAIB's investigation will continue to consider the driver's actions
>>>>> and factors that may have influenced them, including the industry's
>>>>> arrangements for advising drivers about poor adhesion conditions and
>>>>> the guidance and instructions relating to reporting low adhesion and
>>>>> driving in such conditions.
>>>>
>>>> What's to read between the lines in that?
>>>
>>> OK, I was being polite about "reading between the lines", if you think
>>> they were a bit more explicit than that.
>>
>> The options seem to be:
>>
>> - the driver should have been driving more defensively
>> - the TOC should have done more to warn the driver
>> - NR should have treated the railhead more assiduously
>
> - and perhaps NR should have done more to warn the driver
> - and the previous driver to stop at the signal that day might have
> better reported the conditions up the chain of command
>
>> and all the implications that arise from those three, not mutually
>> exclusive things.
>
> As with many accidents there's a bit of a "Swiss Cheese" (alignment of
> holes) flavour, with engineering works etc disrupting normal operations.
> I wonder if a nine-car train would have stopped sooner, for example.

Yes, I think it might, for two reasons:

- There's a greater chance of some of 36 axles encountering short, grippy
sections of track than only 12

- There's a chance that the passage of additional axles will have cleared
some of the crud off the railhead.

ColinR <rail@greystane.shetland.co.uk> wrote:
> On 22/02/2022 00:53, NY wrote:
>> On 21/02/2022 22:08, Recliner wrote:
>>> <martin.coffee@round-midnight.org.uk> wrote:
>>>> https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1055846/IR012022_220221_Salisbury_Tunnel_Junction.pdf
>>>>
>>>>
>>>>
>>>
>>> Three paras stand out:
>>>
>>> 42 With reference to the RHTT programme, the Wessex route Autumn working
>>> arrangements document stated that ‘Wessex aspire for all routes to be
>>> covered once in 24 hours throughout the Autumn period.’ On weekdays
>>> (Monday
>>> to Friday) two RHTT were scheduled to operate over each section of line
>>> each day. The working arrangements document stated that this was ‘to
>>> maximise the chance of each site being treated at least once [every 24
>>> hours]. One set of circuits run at weekends.’
>>>
>>> 43 On the day of the accident (a Sunday), the RHTT that was due to treat
>>> Salisbury Tunnel Junction on the down main line at 17:03 hrs had not yet
>>> passed through the area because it had been rescheduled. This
>>> rescheduling
>>> meant that it would (but for the accident) have passed the junction at
>>> around 23:00 hrs. The revised schedule, which was a consequence of
>>> planned
>>> engineering work between Southampton and Brockenhurst, meant that there
>>> would have been an interval of 36 hours between the RHTT runs over the
>>> weekend.
>>>
>>> 44 The last RHTT to run over the junction passed over it at 11:06 hrs
>>> on 30
>>> October, around 32 hours before the accident occurred. This RHTT
>>> delivered
>>> high-pressure water jetting, and although it could apply adhesion
>>> modifier
>>> gel, it was not required to do so on this section of track.
>>
>> I presume the period of 24 hours has been found empirically to be the
>> longest that still gives an acceptable level of adhesion if a train uses
>> the track just before RHTT train is due, ie with just under 24 hours of
>> grot build-up.
>>
>> Is wheelslide on braking a new phenomenon, or did it also exist with
>> loco-hauled trains (as opposed to multiple units) with their heavier
>> axle loads on the loco's driving/braked wheels. Did tyre brakes on steam
>> locos help to keep the tyres and hence the rails more clear of leaf
>> mulch? Did fewer trees on cuttings in the old days help a lot? Or has it
>> always been a problem?
>
> Yes, there were slipping problems in steam days, not just from leaves.
> Just look at videos of Bullied Pacifics trying to start a heavy train
> out of Waterloo!
> https://www.youtube.com/watch?v=iKzRNrDH5AU
> https://www.youtube.com/watch?v=jWNa2k0PSsM
>
> As Graeme says, speeds were much slower.
>

I remember a few years ago when City of Truro visited the Worth Valley
Railway, it really couldn’t get the train going at Keighley because of
slipping. It took several attempts to start the train uphill round the
curve at Keighley.

--
Jeremy Double