Signal Sighting - Capturing Best Practice
Building a corporate memory
If drivers can't read signals, the likelihood of a signal passed at danger and possible consequences beyond, are higher. Signal sighting assessment processes have been used and documented by industry for almost as long as conventional signalling has been in operation, and regularly re-informed by opportunities to review and learn from operational experience.
For example, the Southern Railway issued 'Memorandum for Guidance of Sighting Committees' (WX785) in August 1946, running to six pages, dealing almost exclusively with semaphore signals. Further editions of this document appeared at frequent intervals for the British Railways Southern Region. Other regions had their own publications. The first British Rail corporate document appeared in 1989 – 'Code of Practice for Signal Sighting' (CP8), followed by its inclusion in a Joint Departmental Procedures Handbook as JDP C005. The first Railway Group Standard (RGS), GK/RT0037, appeared in October 1994.
On 5 October 1999, a passenger train left Paddington and passed SN109 signal at danger, and then collided with an intercity train coming into London with a combined speed of 130mph. 31 people died and more than 500 people were injured in the Ladbroke Grove rail accident. The executive summary of Lord Cullen's report into Ladbroke Grove stated that "The Group Standard on signal sighting is in need or revision in a number of respects…" Railway Group Standard (RGS) GKRT8037 was published in 2001, followed shortly by GERT8034, a new standard on maintaining signal visibility.
Fifteen further years of experience and changes to legislation have provided the latest opportunity to collate definitive industry best practice on signal sighting assessment, and this is contained in the latest Rail Industry Standard, RIS-0737-CCS Signal Sighting Assessment Requirements, published in June 2016.
If you are involved in signal sighting, possibly working as a signalling engineer for an infrastructure manager such as Network Rail, then this new standard will be highly relevant to your work. If you or your company documentation have traditionally referred to older standards, such as Railway Group Standard GERT8037 which was withdrawn in June 2016, then you will need to refer to the new RIS, and talk to your employer about how they will be implementing it. This will also be of interest if you are involved in rail operations, in train driving or signalling more generally, or in infrastructure projects.
What do rail companies need to do today?
RIS-0737-CCS is designed to help rail companies meet their legal obligations particularly those set out in the Common Safety Method on Risk Evaluation and Assessment (CSM RA). It sets out the industry-agreed approach to signal sighting assessment, combining the best of existing practice from old standards as well as new guidance to support compliance with regulatory updates.
Just like older standards, the RIS will help companies in a range of situations including before a new signal is put into use, but also any other change which could affect sighting of a signal including modifying existing signalling infrastructure, installing overhead electrification or using different types of rolling stock, or even changing the way trains are operated (for example, a different stopping position).
Companies will also want to act on reports of poor signal sighting, whether that's via drivers, signallers, managers, indeed anyone working on the railway. Drivers, in particular, will experience first-hand how easy it is to read signals and indicators.
A new block of flats, bridge, road, indeed any change to the built environment can directly obscure a signal, or create a new distraction. Likewise, nature can intervene, especially trees and bushes, to cause a signal or indicator to be less easily seen.
An incident or accident investigation, by a company itself or by another agency like RAIB or ORR, could also recommend a signal sighting assessment.
What have we done to help?
To publish the new standard, we have worked with industry signalling and human factors experts to analyse the interfaces between the lineside signalling system and the train driving task in order to confirm and update the existing requirements for signal sighting assessment and identify the rationale explaining why these are the requirements.
The standard provides a complete set of requirements, rationale and supporting guidance covering:
- The signal sighting assessment process: plan, do, review
- What needs to be assessed to confirm that the signalling asset is compatible with the train driving task at that location – What affects readability? What requires additional reading time? What else adversely affects signal sighting?
- Signalling asset performance – calculations for required readable distance and the corresponding driver's response time
- Signalling asset configuration – best practice for how to lay out signals and indicators
- Additional supporting guidance :
- Designs that are available as reference systems
- Relationship with the Signal Overrun Risk Assessment Process
- Factors relating to the capabilities and limitations of the human eye that can affect signal sighting
You can find the new standard, RIS-0737-CCS Signal Sighting Assessment Requirements, in the Standards Catalogue on the RSSB website.
How is your organisation using the standard? We would be interested to hear from you – so please get in touch with us with your feedback, or if you have queries, via the RSSB Customer Self-Service Portal.