AGENDA ITEM: 02
MEETING:
RSSB Board Meeting
DATE:
06 March 2014
SUBJECT:
Signals Passed at Danger (SPAD)
SPONSOR:
Len Porter
AUTHOR:
John Abbott
1.
Purpose
This paper seeks to update board on SPAD risk, draw some conclusions and
propose the need for a cohesive risk control strategy. The paper will be
supported at the board by a number of industry experts.
2.
Current risk performance
2.1
A comprehensive review of SPAD risk performance over the last 10 years
was provided to the board in a paper to the May 2013 meeting (copy
available upon request).
2.2
The sustained practical application of control measures has improved
industry performance and reduced the level of underlying SPAD risk from 8.2
FWI/year in 2001 to 0.82 FWI/year today[1], which represents a 90% reduction
in risk. Total accidental system risk is currently 139.2 FWI/year, of which train
accidents contribute 5.9% (8.2 FWI/year). SPAD risk accounts for 10% of
train accident risk and 0.59% of total accidental risk.
The reduction in the total number of SPADs and the assessed level of relative
risk is plotted in Chart 1. It is interesting to note that the average number of
SPADs in the 1990s was 774 per year, peaking at 881 in 1998/99, compare
with the annual average of 254, and the current level of 297 this year.
Chart 1 – Change in level of underlying SPAD risk since March 2003
600%
Underlying risk (annual moving
average)
Normalised by Miles (since 2006)
500%
Number of SPADs (annual
moving total)
Normalised by Miles (since 2006)
450
400
400%
350
300
299
250
300%
200
September 2006
baseline = 100%
200%
150
100
100%
0%
2003
[1]
70%
50
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
0
2014
Safety Risk Model Versions 2 and 7
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AGENDA ITEM: 02
2.3
Since Ladbroke Grove in October 1999 no SPAD caused train collisions or
derailments have resulted in a passenger or workforce fatality. There have,
however, been 50 SPAD caused derailments and 4 SPAD caused train
collisions – see Annex A for more detail.
2.4
System level risk commentary
The risk from SPADs is primarily driven by the number of events where the
train reaches the conflict point and there is the potential for a passenger train
collision. 2013 was very similar to the 5 year average 2008-2012 as shown in
the table below and hence the current risk is similar to the average of that
period.
Potential outcome
Average
2008-2012
167.8
8.2
159.6
2013 % Change
Passenger collision
171
reached conflict point
8
stopped before
163
Non-passenger collision / Derailment /
Level crossing collision / Possession
84.6
81
incident
1
Zero risk event
31.6
43
Notes:
1
Zero risk events: SPADs where the train would have had to pass another
signal at danger to reach the first potential conflict point.
2%
-2%
2%
-4%
36%
2012 was an unusually good year for SPAD performance against the 20082012 average, with 2013 being a reversion to the mean. The reasons for the
return to the average are unclear, and are likely due to a variety of factors.
Given the low numbers it is quite possible this is simply random variation.
Analysis has been undertaken to investigate if there is any link between
periods of poor performance and SPAD incidents, initial investigations have
found no evidence of a correlation. However, we should acknowledge that
2012 was characterised by a year of very good operational performance. We
are looking to obtain data on the number of red aspects approached which
we anticipate will have a strong correlation with SPAD numbers (see Annex
C, 4.10).
2.5
International comparison with other rail systems
In 2010 the GB had a SPAD rate of 0.585 per million train km, which is below
the average European SPAD rate of 0.741 per million train km. A number of
major western European railways have suffered serious SPAD caused train
accidents over the past 4 years including: Belgium and the Netherlands in
2010, Germany in 2011, the Netherlands, Germany, and Switzerland x 2 in
2012.
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AGENDA ITEM: 02
3.
Performance by operators and routes
3.1
Operators
 Individual train companies typically have very low SPAD numbers, and
so any change between years will often simply be a result of random
variation.
 Passenger train operators had a 4% increase in their SPAD numbers
in 2013 against the five year average of 2008-2012, and freight
operators had a 17% increase.
The individual performance of passenger and freight operators including
normalisation is contained within Table 1 of Annex B, for comparison
purposes.
5 Routes have seen an increase over the same period, with 3 experiencing a
large increase in more significant SPADs as seen in Table 2 of Annex B.
4
Factors that affect SPAD performance and risk
4.1
The factors that affect SPAD performance and risk are varied and multifaceted and which have been and continue to be the subject of considerable
analysis and review, including:
4.2
The findings of Network Rail ‘Deep Dive’ Review and Safety Bow Tie
exercise.
4.3
The need for fit for purpose and continuous improving Safety Management
Systems (SMS).
4.4
Challenge of the ‘as is’ infrastructure:
 Signal risk assessment
 Multi-SPAD signals
4.5
The opportunities and risk posed by infrastructure investment schemes.
4.6
Human performance of train drivers.
4.7
Environmental conditions – poor adhesion conditions or assessing the effect
signals being obscured by sunlight.
4.8
The effects of timetabling and performance on SPADs.
4.9
Ensuring Train Protection Warning System (TPWS) remains an effective and
reliable system for decades to come.
4.10
Delivering and managing the European Rail Train Management System
(ERTMS) fitment programme.
4.11
Risk methodology - making sure we have robust SPAD and signal risk
assessment tools that people can understand and use to make informed
decisions.
4.12
Red aspects approached - obtaining good estimates of the actual number of
red aspects approached at signals to support more effective SPAD risk
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AGENDA ITEM: 02
assessments and benchmarking. A research project is now underway to use
signalling control centre data to obtain this information in a usable form.
The potential influences of each of the areas identified above are described in
more detail in Annex C. (Note that the clause numbers in the Annex
correlate to those in this section).
5.
Conclusions
5.1
SPADs account for a relatively low level of long term residual system safety
risk. However, they do carry the potential for a high consequence accident
which would generate a significant amount of reputational risk for the
industry.
5.2
SPADs represent a system interface risk which all Safety Management
System (SMS) holders have a responsibility to control and manage.
5.3
The industry continues to invest considerable resources and efforts to
mitigate SPAD risk. These efforts have been successful in driving improved
performance but this improvement has now plateaued and therefore it is time
to refresh the approach and make fit for purpose for the next 10 years.
5.4
The challenge facing the industry is to further improve risk control
performance without devoting disproportionate resources given the small
residual risk, and therefore our final conclusion is that a cohesive industry
strategy is required to coordinate industry improvement actions over the next
10 years.
5.5
It is anticipated that such a strategy would feature a vision, improvements to
current tactical controls, identification of game changing opportunities, the
use of new technology (along with associated risks), future risk methodology,
tools and competence.
It is proposed that such a strategy is developed by the System Safety Risk
Group (SSRG), however SSRG will need to secure appropriate input from
other relevant sponsorship bodies so that it is genuinely system based. The
strategy would then need to be underpinned by action plans developed by
individual SMS holders as well as the joint safety improvement plans between
all SMS holders. SSRG has the capability to facilitate this as part of the newly
established safety cooperation arrangements.
6.
Recommendations
6.1
The board are invited to:



UNDERSTAND the low level of long term residual risk posed by
SPADs but also RECOGNISE that a high consequence train accident
could still happen any time
NOTE that over the past 10 years the industry has devoted significant
efforts to improve SPAD risk but is now time to review, refresh and
make fit for purpose for the next 10 years
SUPPORT the proposal to develop an appropriate10 year risk control
strategy
RSSB Board Meeting Final: 06 March 2014
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Annex A
Information on the train collisions caused by a SPAD since Ladbroke Grove
The four train collisions were:
Darlington in October 2009 – mid-platform SPAD resulting in slow speed collision
with train standing ahead in platform. Two major injuries reported. Cause was
determined as contamination (leaf/vegetation) of rail head.
Norton Bridge in October 2003 – an intermodal freight train collided with a stationary
freight train on the same line. No reported injuries. Driver error was determined as
the cause (failure to react to caution signal).
Hither Green in March 2001 – a passenger train had a slow speed collision with the
rear of another passenger train after running through points. 10 minor injuruies
reported. Cause was determined as driver error (failure to check signal aspect).
Lewes in October 1999 – an empty coaching stock shunt movement collided with
the side of a passenger train. No reported injuries. The cause was determined as
driver error (failure to check signal aspect).
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Annex B
Table 1 - Performance of individual TOCs and FOCs
Footnote:
1. If a driver is not deemed responsible for a SPAD then these incidents will not
get attributed to the train company and therefore are not reported here.
2. Any incident attributed to OTM operators are not reported here.
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Annex B
Table 2 – Performance of Network Rail Routes
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Annex C – Factors that affect SPAD performance and risk
Supplementary information
4.2
SPAD Deep Dive Review and Safety Bow Tie exercise
During the course of 2013, Network Rail undertook a ‘deep dive’ review of
SPADs to provide assurance on the management of the risk. The review
identified a number of findings, some of which are listed below:









4.3
A high performance railway present the lowest number of red signals to
a train driver reducing exposure rates and the potential for error – there
is currently no method to measure driver exposure to red signals
TPWS has limitations in its effectiveness where train speeds are high,
braking force is less than 12g or if railhead adhesion is poor.
Current industry understanding of the SPAD issues suggests the risk is
unlikely to reduce significantly until the introduction of further technical
solutions, e.g. European Train Control System (ETCS).
Human error by the train driver is by far the single biggest cause of
SPADs and it is considered limits of human performance are being
reached.
There are indications that the rate of ‘avoided SPADs’ through TPWS
intervention are increasing
Light locomotives and empty coaching stock (ECS) moves are involved
in a disproportionate number of SPAD incidents
Freight services in general have a higher number of SPAD incidents
compared to passenger services (normalised).
A disproportionately high number of SPADs occur at Ground Position
Light (GPL) signals, linked with freight and ECS SPADs.
Vegetation management can reduce the SPAD risk by providing a clear
unobstructed view of signals, reduce the effects of low adhesion when
braking and provide designed braking force in the event of TPWS
intervention.
Safety Management Systems (SMS)
Safety of the modern railway system is delivered by the practical operation of
fit for purpose SMSs. These will identifiy and quantify risk, specify controls,
define cooperative working arrangements, and contain a suitable assurance
regime.
SPADs represent an interface risk between operators and infrastructure
managers which require suitable controls to be specified, applied and assured
as part of each company’s SMS. Failure to adequately specify or consistently
apply SMS based controls has the potential for serious consequences.
4.4
Management of the ‘as is’ infrastructure


Signal risk assessment
Multi-SPAD signals
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Annex C – Factors that affect SPAD performance and risk
Management of the infrastructure can reduce the potential for SPADs through
reducing exposure to red signals; the primary focus of maintenance activity for
example is to make sure the signal displays a clear and unambiguous aspect
to the train driver and reduce the incident of red signals through infrastructure
failures. There is a requirement to risk asses all signals to identify signals that
may have a combination of characterises which may them more vulnerable to
high consequence SPAD event and the Signal Overrun Risk Assessment Tool
(SORAT) has been specifically developed for this purpose. Other factors
include renewal of assets, timetabling, capacity planning, and operation of
signalling equipment by signallers.
A number of signals on the network have been passed multiple times and
these multi-SPAD signals are important to consider as 6% of SPADS in the
last 5 years have been at signals which were multi-SPAD at the time, and
21% of these had at least one SPAD in the preceding 5 years.
Special of arrangements are in place to consider whether there is some
property of these signals which make them more prone to SPADs. These
include the set-up of the infrastructure, and further reasonable practicable
enhancements.
The number of multi-SPAD signals continues to reduce from 154 at
September 2011 to 124 now (21% reduction) and 85 (68%) have TPWS fitted.
There are encouraging signs that this downward trend in numbers is likely to
continue although it has slowed over the past year.
Only 2 multi-SPAD signals have been subject to more than 1 high risk SPAD
in the past 5 years. Action has been taken at both locations to reduce the
probability for further events.
4.5
Infrastructure investment schemes
Significant infrastructure investment schemes can pose a risk in relation to
putting in place temporary and permanent layouts and signals (eg sighting
problems following installation of OHLE). This investment should reduce
SPAD risk but does require input from operators and Network Rail to make
sure the work is properly planned.
All junction signals protecting conflicts are now mitigated by TPWS following
the regulated fitment in the early 2000’s however significant changes to the
infrastructure have the potential to affect SPAD risk and consideration is given
to this as part of the design and deliverability phase of any new scheme.
The simplest layout is the easiest to signal and has lowest potential risk, but
does not meet the needs of a growing network and therefore operational
flexibility is required which increases the opportunity for conflicts. Designers,
supported by operational experts (NR and TOC) use signal risk tools (e.g.
SORAT) to consider the balance of risk on new schemes based on timetable
and layout modelling, and this is approved by a Major Schemes Review Panel
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Annex C – Factors that affect SPAD performance and risk
(MSRP) to validate that risks have been reduced so far as reasonably
practicable.
Some key principles are established within design, including reducing the
application of controls that can require signals to be approached at red and
wherever possible functionality and controls are adopted that allow SPAD risk
to be reduced e.g. TPWS, flank protection, swinging overlaps, etc.
All new signalling works utilise high performance LED optics for all aspects
and indications greatly increasing readability. The optimum placing of signals
is key to reducing future SPAD potential and signal sighting is a key aspect of
new schemes using a variety of tools; computer 3D models, HD video and
other photogrammetry tools, which assist to locate the best signal positions in
accord with industry standards The signalled layout is then modelled into
driver training/simulation for familiarisation of new layout.
The increase in use of overhead line electrification also has the potential to
introduce SPAD risk through obscuration of signal aspects, especially on
curved approaches, and the sighting of signals is a key aspect of the design.
4.6
Training and management of Train drivers
By far the biggest cause of SPADs is distraction/concentration loss by the
Train Driver involved in the incident, either on approach to the signal at red or
lack of response to cautionary aspects in the sequence approaching the
signal at red. Annually there are over 528 million passenger train kilometres
and some 588 million train kilometres. There are approximately 35,000
signals on the network and it is estimated the exposure rate to red signals is
tens of millions a year. Over the past four years there has been an average of
276 SPADs a year so for a risk that is still primarily controlled by the actions of
a human (the driver), this represents an extremely low error rate, and whilst
recognising that it has been suggested the limit of human performance may
have been reached, recent pieces of industry research have lead to
improvements in the areas of incident investigation for Driver Managers and
training and assessment in non technical skills for Train Drivers and Driver
Assessors.
More work is underway to better understand the human factor elements of
SPADs in a changing environment, building on the work that has taken place
over the decades to address new risk indicators, for example the number of
TPWS interventions on the approach to red signals is not driving SPAD
numbers up (the system is stopping the train as designed) but is an indicator
that residual SPAD potential exists especially where TPWS is not fitted.
The objectives of this RSSB study requested by Network Rail following its
‘deep dive’ into SPADs are:
•
•
To understand the human factors issues associated with SPAD incidents
Draw together information on how industry manages human factors issues
associated with SPAD incidents
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Annex C – Factors that affect SPAD performance and risk
•
Identify good practices in managing the human factors associated with
SPADs and possible areas for improvement, based on the human factors
review
The outputs of this study are expected in early 2015.
In response to the Network Rail ‘Deep Dive’ Review, a study is in the early
stages of development to further research into SPADs involving empty
coaching stock and light locomotives.
4.7
Environmental conditions
Over the last ten years, approximately 1.6% of SPADs have been recorded as
being due to environmental conditions beyond the drivers’ expected control. A
further 1.8% is due to the driver misjudging environmental conditions.
Together these account for less than 3.5% of SPADs. In contrast, disregard
and misread errors account for approximately 86% of SPADs. However, the
influence of poor adhesion can dramatically increase SPAD risk due to the
effects it has on TPWS effectiveness. A number of recent incidents have
brought this into focus.
Please see the CEO report for details of two high risk adhesion related
SPADs in December and January.
4.8
Timetabling and performance
The reliability of the timetable can materially influence the numbers of red
signals to which a driver will be exposed – a high performing railway is a safe
railway. With the ongoing desire to accommodate additional services and
service improvements on the existing network, the need to continuing fit in
extra paths, run longer trains to existing timings and improve certain journey
times, all have the potential to affect performance and increase red signal
exposure. The industry needs to enable decisions to be reached on the
appropriate level of trade-off between key factors such as journey time,
capacity and performance, such as a change control mechanism.
Analysis of initial performance loss suggests issues with the base timetable
and how this impact gets worse as the service is aggregated from individual
trains to service groups, TOCs, sectors and nationally. Limited studies have
shown the root cause of many of these ‘common cause’ delays is deficiencies
in the dataset (the Timetable Planning Rules) used to create the timetable and
operational plan.
As the network has become more congested it is increasingly important that
the values used in planning the timetable are achievable in daily delivery, and
that daily delivery focuses attention on achieving them - with the effects of not
meeting them being magnified and red signal exposure rates increase.
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Annex C – Factors that affect SPAD performance and risk
There are a range of factors including changes in rolling stock, longer trains,
extended dwell times, station dispatch and turnaround times, sectional
running times, professional driving techniques and junction margins all having
an influence on this.
Plans have been developed in collaboration with the industry, to address train
planning and capacity considerations in improving performance. The plans
cover:
 Approaches to how improvements can be made in our confidence, and
accuracy of, the timetable planning rules - the key building blocks for
capacity allocation
 How we manage the specification of timetables and manage change
 The introduction of traffic management technology
This focus on smaller / reactionary / operational delays, which are a
consequence of the complexity of the interactions in the base timetables and
the attention to detail in delivery of the operational plans will improve
performance and thus reduce the number of red signal exposure. However,
solutions will require more radical strategies, jointly with the TOCs, to address
potential ‘step change’ opportunities. This requires cross industry
collaboration around:


improving the robustness of timetables including recovery and
resilience
introducing traffic management system (TMS) across the network.
TMS is a signalling and control system, which offers a range of decision
support tools. These will help run the network more effectively by predicting
and managing timetable conflicts proactively. Bringing this technology in
quicker provides opportunities to improve train service control decisions and
implement better service management and recovery during incidents.
Both improving the robustness of timetables and TMS implementation will
require collaboration from train operators, and support from DfT and ORR, to
be efficient and effective.
4.9
Train Protection Warning System (TPWS)
TPWS was implemented in GB as an interim measure to reduce the risk from
SPADs, pending implementation of full protection through systems that
monitor driver performance continuously. However the European Rail Traffic
Management System (ERTMS) fitment programme is now such that TPWS is
likely to remain the primary train protection system on many routes for
decades to come.
TPWS is installed on around 13000 main aspect signals protecting junctions,
650 buffer stops and 1150 permissible speed reductions plus a number of
other locations where its fitment has been considered to be reasonably
practicable.
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Annex C – Factors that affect SPAD performance and risk
Since the completion of installation at the junction signals in 2003, and in
conjunction with other risk reduction measures, SPAD risk has reduced by
90%. Over this period TPWS has proved to be a very reliable system with the
probability of TPWS failing operate on demand following a category A SPAD,
due to an undetected fault of TPWS equipment, has been around 0.005% (1
in 2000 SPADs). However on 41 occasions (2%), following a category A
SPAD where TPWS operated correctly, the driver has incorrectly reset the
system and continued with the train journey.
This phenomenon, now known as ‘reset and continue’, was unforeseen at any
level within the industry at the time of development and implementation of the
TPWS system and therefore was a risk that was “unmanaged at that time”.
‘Reset and continue’ is now both recognised and proactively managed within
the industry.
In November 2009 the TPWS Strategy Group was set up to help ensure the
long term viability of TPWS. Part of the remit of the group is to monitor the
reliability of the system with a new programme of work being recently
established to ensure that we understand what the reliability requirements of
TPWS should be going forward and how we should monitor against the
requirements. Completing and promoting the industry response to reset and
continue has also been a key part of the group’s work.
4.10 European Rail Train Management System (ERTMS)
ERTMS is the European Rail Traffic Management System. This is made up of
Euroradio (GSM-R), the European Train Control System (ETCS), European
Operating Rules and the European Traffic Management Layer.
Euroradio uses GSM mobile telephone technology adapted for railway use,
known as GSM-R. There are additional safety protocols compared to public
GSM and it operates on its own frequency band. GSM-R is used to support
both voice and data transmission between track and train and in particular is
the data bearer for ETCS.
ETCS is a cab-signalling system that incorporates automatic train protection
(ATP). Equipment on the train provides the driver with information about how
fast and how far the train can safely travel. The driver is responsible for
driving the train, but if the train determines that it is going too fast or too far it
will provide the driver initially with a warning and unless sufficient action is
taken, will automatically apply the brakes. There are different variants of
ETCS, called levels.
Given how the GB rail network operates there is a very complex relationship
between rolling stock operation and roll-out of ETCS. Since late 2001 the
industry has been working together on this through the ERTMS Programme,
now under Network Rail leadership. Through this Programme a cost-effective
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Annex C – Factors that affect SPAD performance and risk
rollout of ERTMS has been planned that attempts to closely align rolling stock
and infrastructure fitment.
GSM-R is now in operation throughout most of GB supporting voice
communication and on the Cambrian Line in Wales and a test line near
Hertford, data communication as well. Rollout of GSM-R to all train fleets and
all infrastructure for voice operation will be complete in 2014. In the south of
England legacy National Radio Network (NRN) equipment has already been
decommissioned; in due course NRN and Cab Secure Radio (CSR)
equipment can be decommissioned nationwide.
Upgrades to GSM-R may be required to support higher quality of service
requirements of data transmission as ETCS is deployed.
ETCS has been in successful operation on the Cambrian Line from
Shrewsbury (exclusive) to Aberystwyth and Pwllheli since March 2011; this is
ETCS Level 2 without lineside signals. ETCS Level 2 application on the Great
Western Mainline from London Paddington to Bristol, Newbury and Oxford is
underway to enter service progressively from 2017 onwards, lineside signals
will be retained. The Thameslink core section (Kentish Town – London
Bridge) features ETCS Level 2 from 2017 with automatic train operation soon
after, some lineside signals will still be provided. The East Coast Mainline is
the first mainline application without lineside signals; planning is underway
and commissioning is likely to be in 2020, although the date is to be
confirmed.
4.11
Risk methodology
The underlying level of risk at each signal is currently assessed using the
Signal Overrun Risk Assessment Tool (SORAT), with each signal being
assessed on a 5 year assessment cycle. However, given this 5 year
assessment cycle the method does not give an estimate of the overall level of
risk from SPADs that can be used to monitor changes in SPAD risk on an
ongoing (month by month) basis.
At the time TPWS was introduced the industry had no means of monitoring
the change in risk that would occur as a result of TPWS and therefore the
SPAD Risk Ranking Tool (SRRT) was developed and implemented in 2002.
This method enables an estimate of the change in SPAD risk on a monthly
basis to be made based on the SPADs that have actually occurred over a
rolling 12 month period and asking the questions:
1. Given the SPAD that occurred, how likely was it that an accident could
have occurred?, and
2. If an accident had occurred what would the potential consequences have
been in terms of fatalities and weighted injuries?
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Annex C – Factors that affect SPAD performance and risk
The SRRT is a measure of the relative change in risk from the total number of
SPADs occurring in a given year compared to a base year. It is not a measure
or quantification of the absolute level of risk from SPADs.
The method was designed to be easy and relatively quick to use while giving
a good indication of how risk changed when compared to the base years of
initially 2001 and then 2006. Because of the need for it to be relatively quick
and easy to use it was necessary to make some assumptions and
simplifications within the method. In view of this, while the relative level of risk
for the SPADs that occur over a 12 months period is considered to be
reasonable, inconsistencies may seem to exist when comparing or reviewing
SRRT scores for individual SPADs.
When reviewing the SRRT score for an individual SPAD it is important to note
that the score DOES NOT relate to the underlying level of risk associated with
the operation of that signal. The underlying level of risk at each signal is
derived from the SORAT taking into account the risk from ALL the potential
train approaches and conflicts that can occur at the signal in a year not just a
single SPAD that occurs at the signal.
So, a “good” signal, ie one which is well sighted, no distractions, adequate
safe overrun distance, etc, with a low level of underlying risk (as calculated by
SORAT) can still experience a “bad” SPAD which has a high SRRT score due
for example to the driver’s loss of concentration or poor adhesion conditions.
Conversely there can be a low SRRT score SPAD, eg a non-hazardous
goods freight train passes the signal by only 1m at night and could only collide
with another freight train, at a “bad” signal which has a high level of underlying
risk because it has a short overrun distance and experiences a high level of
passenger train interactions during the day.
A high SRRT score for a SPAD at a signal therefore does not mean that it is a
high risk signal and a low SRRT score does not mean that it is low risk signal.
A SPAD with a high SRRT score is just one of the indicators that can be used
to prompt Network Rail to look at the SORAT assessment for the signal to
check that nothing has been missed. No changes to a signal should be made
based solely on an SRRT score for a single SPAD.
That said, in discussions with Network Rail it is been concluded that, as the
SRRT methodology is now 12 years old and, in light of the development the
SORAT algorithms, this is a good time to review the SRRT methodology, its
training requirements and the way it is communicated to ensure that the
SRRT remains fit for purpose. A plan and specification for this review is being
developed.
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Annex C – Factors that affect SPAD performance and risk
4.12 Red aspects approached
Carrying out an accurate signal risk assessment relies on estimates being
made of the number or red aspects approached by trains at each signal per
year. To date this has been done using algorithms within the various models
that exist such as SORAT. To improve the accuracy of the signal risk
assessments RSSB has contracted Huddersfield University (through its
recently established strategic partnership) to develop a software tool to extract
the actual recorded red aspects approached data for individual signals (where
possible) in a given year from the Network Rail operational data feeds, which
provide data to Network Rail’s Control Centre of the Future application (CCF).
The TPWS strategy group is also overseeing the work.
Use of this data for risk assessments and the normalisation of SPAD data will
provide a significant improvement in our ability to make informed decisions on
managing SPAD risk.
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