AS 7631 Railway Infrastructure - Sighting

The objective of this Standard is to provide a framework to assess optimal sighting arrangements in order to minimize risks as a consequence of poor sighting on the railway network.

The key points of this Standard focus on providing a framework for optimal sighting arrangements, risk mitigation, and detection-response considerations. Firstly, it establishes a structured framework to ensure the correct placement and sighting of signs, signals, and indicators in the railway environment, helping railway personnel detect, interpret, and respond appropriately to visual cues, thereby reducing the risk of accidents and errors caused by poor visibility or suboptimal positioning.

Secondly, the Standard emphasises conducting thorough sighting assessments, considering factors such as line of visibility, lighting variability, and potential distractions. These assessments are essential for identifying and mitigating risks related to poor sighting conditions, such as signal misinterpretation or the failure to see critical signs due to environmental or infrastructural constraints.

Finally, the Standard outlines the importance of understanding the detection-response process. It stresses the need for optimising the placement and design of visual stimuli to ensure they can be detected and acted upon promptly, taking into account factors like visibility, peripheral vision, and the depth of processing required for various signs and signals.

Two main changes have been made since the last review. First, the roles of the signal sighting committee and the skills needed for its members are now clearly defined, which also helps inform other standards. Second, a new Appendix C has been added that explains how to calculate letter sizes based on how far away they will be viewed.

This product improves safety and interoperability in several ways. First, it promotes consistent placement of signs and signals across different rail networks. By following the guidelines in AS 7631, railway operators can ensure that signs and signals are positioned uniformly, which improves interoperability when different operators or personnel work within the same network. This consistency helps reduce confusion and ensures safe operations across various railway systems.
Secondly, the Standard aligns with other relevant standards, such as AS 7632 (Railway Infrastructure – Signage) and AS 7721 (Railway Signals, Indicators, and Signage). This harmonisation ensures that different aspects of railway infrastructure sighting follow the same guidelines, making it easier for various rail systems to operate together effectively.
In summary, AS 7631 enhances safety by reducing risks related to poor sighting and supports interoperability through consistent and harmonised practices across different rail networks.

AS 7631 addresses several key risks associated with poor sighting of railway signs, signals, and indicators. The primary risks managed through this Standard include:

1. Signal Passed at Danger (SPAD) Risks: The Standard requires sighting assessments to ensure signals are optimally placed and clearly visible, reducing the likelihood of SPAD incidents.
2. Incorrect Signal or Sign Interpretation: By setting guidelines for proper placement, lighting conditions, and minimising visual distractions, the Standard helps prevent misinterpretation or confusion between nearby signals or signs.
3. Obstruction of Critical Signals or Signs: The Standard mandates sighting assessments to identify potential obstructions, such as buildings or vegetation, and ensures that solutions like repositioning signals or adjusting infrastructure are implemented.
4. Glare and Lighting Variability: It addresses issues related to glare and changing light conditions by ensuring signals are positioned to avoid these problems or by implementing measures like shielding or increased sighting distances.
5. Distractions and Parallel Line Hazards: The Standard calls for an assessment of distraction factors, ensuring signals are placed to reduce confusion from parallel lines, background interference, and other distractions.
6. Inadequate Detection-Response Time: It establishes minimum detection-response times based on line speeds and other relevant conditions, ensuring personnel have enough time to see and respond to visual cues effectively.

To implement this Standard within your organisation, it is recommended to follow this approach:

1. Conduct a gap analysis: Review current practices and compare them with AS 7631. Identify any gaps, such as poor signal placement or lighting issues.
2. Establish a Signal Sighting Committee: Form a committee as described in the Standard, including signalling engineers, rail traffic crew, human factors experts, and safety personnel. This committee will oversee sighting assessments and ensure compliance.
3. Integrate sighting assessments into operational procedures: Regularly assess the sighting of new installations and existing infrastructure. Consider visibility, lighting, glare, distractions, and obstructions. Make sure assessments account for detection-response times.
4. Train personnel on the Standard:
   Provide training for relevant staff, like signalling engineers and maintenance crews, to help them understand AS 7631’s requirements, including detection-response processes and glare management.
5. Align with other standards: Integrate AS 7631 with other relevant standards, such as AS 7632 and AS 7721. Ensure consistent placement and design of signs and signals across your network for smooth operations.
6. Implement mitigation measures: Based on sighting assessments, take action to improve safety, such as moving signals, clearing obstructions, adjusting sign heights, or adding glare shields.
7. Continuous monitoring and review: Regularly check sighting conditions and review the effectiveness of arrangements. Update them as needed to keep them optimal.
8. Engage stakeholders: Work with other rail industry partners, like contractors and regulatory bodies, to ensure consistent implementation of the Standard across different systems. This collaboration improves safety and interoperability.