Let’s consider Signal Passed at Danger (SPAD) events. What causes them, what are the impacts to passengers, drivers and line controllers, and how can we use a holistic approach to achieve reductions?

If you’ve been involved in operating a railway or tram network, you will have undoubtedly faced the issue of dealing with a SPAD. Commonly, they occur at a known location, or at a particular time of day or whilst drivers are undertaking a particular movement. 

Often there are physical factors contributing to the SPAD such as placement of signals, signal confusion or sunlight impacts. In equal measure, there are human factors to think about. Understanding the human factors contributing to SPAD’s is an essential component of any management system targeted at achieving reductions. 

In this blog, I’ll have a look at some of the common human factors issues and have a think about what we can do to improve matters. 

The character quotations are fictional but represent some of the commonly experienced issues.

Precursors

When looking at SPAD incidents, precursors can be grouped into several subject areas. These include a lack of situational awareness, fatigue and an associated decline in vigilance, training and competence issues, communication and coordination failures, and environmental and ergonomic factors. Organisational and cultural factors can also cause driver stress and pressure.

Drivers may lose focus due to distractions, fatigue, or visual overload caused by infrastructure issues, or the impact of operating in a busy public realm. Expectation bias, (where drivers assume signals will be clear based on a routine such as expected tram priority due to highways signalling pre-emption) also plays a significant role.

This leads us neatly on to the first of the precursors, situational awareness.

Situational Awareness

Linda: ‘That junction is a nightmare. There are cars and people everywhere!’

When we think about situational awareness, we understand it as the ability to perceive, understand, and anticipate events and changes in a dynamic situation. This can become challenging in high-pressure scenarios. It involves being aware of your surroundings, recognising potential risks, and understanding the relationships between different factors that might impact your decision-making. 

Having good situational awareness allows us to make informed decisions and react effectively to evolving situations. 

A lack of situational awareness can contribute significantly to SPAD events by impairing a driver's ability to perceive, understand, and act on critical inputs. A loss of focus or attention often arises from distractions related to external events such as vehicle and pedestrian movements around the tram, cab tasks, or fatigue. 

All of these can reduce Linda’s capacity to notice and respond appropriately to signals. 

Fatigue and Reduced Vigilance

Augustine: ‘I’m tired due to the shifts and my personal life is impacting – but I don’t feel I can mention it when booking on’.

Fatigue and associated reduced vigilance are other critical factors, often stemming from long shifts, insufficient rest, or disrupted circadian rhythms. These are well known factors that can impair a drivers' alertness and decision-making abilities.

Long working hours characterised by extended shifts due to overtime or insufficient rest breaks can lead to cumulative fatigue that depletes cognitive and physical reserves. 

Augustine’s new baby and his reliance on overtime are resulting in a reduction in his alertness, compromising his ability to detect, process, and respond appropriately and in a timely manner whilst he is driving. 

Human alertness naturally fluctuates throughout the day, with performance significantly deteriorating during certain hours, such as early morning, early afternoon, particularly after a meal or late at night. When drivers are required to work during these biologically low periods, their reaction times slow down and their ability to handle complex decision-making diminishes. These factors make them more susceptible to errors, particularly in scenarios requiring quick judgment or high concentration.

In the context of SPAD events, addressing fatigue and vigilance decline requires a considered approach. We should actively consider work-rest balance by developing rosters that rotate forwards and allowing adequate recovery time between shifts and ensuring drivers have the means to report personal concerns without fear of reproach. 

Of course, this can lead to organisational tensions, where costs are impacted and efficiency diminished. The overriding priority must always be safety of course, and the challenge is hitting the ALARP ‘sweet spot’, achieving a viable balance between risk, cost and efficiency. 

Strategies such as optimising shift rotations to align with circadian rhythms, providing education on fatigue management, and using technologies like fatigue monitoring systems can significantly enhance driver alertness without straying into ‘diminishing returns’. 

After discussing his issues with his manager, Augustine is now working flexibly for an agreed period. He is much happier, and his risk profile is reduced!

Training and Competence

Brian: ‘I completed my training six months ago, but I’ve had no review to identify any areas of concern with my performance’.

It seems obvious, but it is proven that training and competence gaps are significant contributors to SPADs, as they can impact a drivers' ability to make accurate and timely decisions with confidence. 

Unfamiliarity with routes because of training deficiencies or irregular driving increases the likelihood of missing critical signals or misjudging stopping distances. This is particularly problematic in areas with complex track layouts such as termini or route junctions, where local knowledge is essential for anticipating signal positions and braking points.

Skill decay further increases the risk of SPADs, as drivers who are infrequently exposed to certain scenarios, such as uncertain signals or emergency situations, may struggle to respond appropriately when these situations arise. 

Without regular monitoring and targeted practice or simulation of such events, Brian’s skills may not develop sufficiently, or may deteriorate over time, reducing his ability to apply them under pressure.

Addressing these gaps requires comprehensive training programs that emphasise route familiarisation and the regular reinforcement of critical skills. Simulators can help drivers practice responses to uncommon but high-risk scenarios, reducing the impact of skill decay. 

Regular competency assessments, particularly in the early stages of a drivers career are crucial for identifying and addressing areas where drivers may require additional support, such as in Brian’s case. 

Communication and Coordination Failures

Fatima: ‘I was running late due to the incident, and I was sure the controller said I could pass the signal at Stop, but there was talking in the background in the OCC, and I didn’t hear him clearly’.

Communication and coordination failures are critical precursors to SPAD events as they can lead to misunderstandings and poor decision-making. 

Miscommunication with OCC staff is a prominent factor, where ambiguous or misunderstood instructions may result in drivers proceeding without proper authority or failing to react appropriately to restrictive signals. This risk is heightened in high-pressure situations, where clarity and precision in communications are essential.

A lack of clear procedures further exacerbates SPAD risks, particularly in the context of degraded or emergency conditions. When operational protocols are inconsistent, unclear, or not thoroughly understood by all involved parties, or where radio communication discipline is poor, drivers and OCC staff may struggle to coordinate effectively. This confusion can delay responses, increase the likelihood of errors, and create situations where stop signals are inadvertently passed.

To make sure Fatima and her colleagues can hear clearly and take instruction effectively, OCC discipline should be non-negotiable, particularly in degraded or emergency situations, with access to the OCC robustly controlled to prevent unauthorised or unwanted staff entering.

Clear and standardised communication protocols should also be implemented and maintained to reduce the likelihood of miscommunication. 

Regular training and simulation exercises for drivers and OCC staff can enhance mutual understanding and ensure consistent application of procedures. 

Encouraging a culture of open and proactive communication, together with simulation exercises held jointly between drivers and OCC staff can improve collaboration and team working, reduce the risk of misunderstandings and improve overall coordination. 

Fatima was included in a desktop training exercise with the OCC team and now she has a better understanding of the pressures of operating the OCC during an incident and the OCC team can now see things from a drivers point of view more clearly. She is now not afraid to ask for a clarification if she is unsure. 

As a result of the training, there is now much more of a team approach during incidents.

Environmental and Ergonomic Factors

Charlie: ‘That signal is hard to spot in the mornings as the sunlight is behind it and shines through the windscreen. This isn’t helped by the sunblind not coming low enough down’.

Environmental and ergonomic factors can significantly influence SPAD events by impairing a drivers' ability to detect and respond to signals appropriately. Poor signal visibility is a major contributor, as signals obscured by sunlight, vegetation, or lineside infrastructure can easily be missed or mis-read. 

Cab design issues can also contribute to SPAD risks by creating distractions or delays to reaction times. Poorly designed cab layouts, interfaces or cluttered displays can divert attention from critical external factors such as signals, particularly in high-stress situations.

Addressing these factors requires targeted interventions, such as route risk assessments and data evaluation to identify improvements to signal placement. Reviews of lineside maintenance and vegetation management to ensure signal visibility under all conditions are essential.

Charlie was involved in a project to look at redesigning cab interfaces to align with ergonomic principles. Although it was initially recognised that this may prove difficult, equipment modifications to the window blinds, cctv systems and seat adjustment now help Charlie and his colleagues drive more safely. 

Introducing advanced technologies, like in-cab signal displays or automated warning systems, can further enhance situational awareness.

Charlie and the other drivers are much happier now the modifications have been done. As a result of the project, the intensity of the signal has also been increased so it can be seen in all conditions.

Stress and Pressure

Bal: ‘The controller is always on your back, you never get a minute’.

Stress and pressure are significant contributors to SPAD events as they adversely affect a driver's cognitive and decision-making capabilities. Operational pressure, particularly the demand to maintain tight schedules can lead drivers to rush decisions, potentially overlooking critical signals or bypassing safety protocols. 

The emphasis on punctuality may create a conflict between adhering to operational efficiency and ensuring safety, heightening the likelihood of errors in judgment or lapses in attention.

Emergency situations, such as unexpected system failures or other unplanned disruptions can also increase stress levels whilst demanding rapid decision making. Heightened stress can also impair cognitive function, reduce situational awareness and slowing reaction times. 

The combination of operational pressure and acute driver (and controller) stress creates an adverse and dynamic environment where Bal’s SPAD risk is significantly increased.

Mitigation strategies can be introduced that encourage a safety focused culture and prioritise safety over strict adherence to schedules. 

Simulation-based training can prepare drivers and controllers to handle emergency scenarios more effectively and robust and clear Standard Operating Procedures for managing disruptions can help to alleviate stress and improve decision-making during critical events. ‘Stress management during incidents’ training is also recommended.

Organisational and Cultural Factors

Elena: ‘There is no formal way to report our concerns. If we mention our concerns to our managers nothing ever happens, so we don’t bother any more’.

Organisational and cultural factors play a crucial role in influencing the occurrence of SPAD events by shaping workplace attitudes and practices around safety. 

Where there is a weak safety culture, there can be a neglect of underlying risk factors. 

Where operational efficiency and schedule adherence takes precedence over proactive risk management, the likelihood of SPADs is increased. 

Without a strong safety culture, employees may feel discouraged from raising concerns or identifying potential hazards and unsafe practices may be perpetuated.

What is your view if you are a business leader or manager? Do you know what is really going on?

Gaps in reporting and poor feedback loops further compound the issue, as the absence of effective mechanisms to capture and learn from near-misses undermines the ability to identify and address contributing factors. 

When we fail to analyse near-misses or share lessons learned, we miss opportunities to implement preventive measures, leaving our organisational vulnerabilities unaddressed. 

A lack of feedback has demotivated Elena and her colleagues from engaging in reporting near misses or safety concerns, thereby reducing organisational knowledge and its ability to proactively address issues.

To mitigate this, we must foster a safety-centric culture where employees feel empowered to report concerns without fear of reprisal and a strong leadership commitment to safety and continuous improvement is vital.

Now Elena’s employer has implemented a near miss reporting scheme, and the data is published together with information on implemented measures identified in the scheme. Elena and her colleagues are now reporting their concerns, feel much more valued, and the companies safety performance is improving.

Wrap up

If we want to reduce SPAD events in our respective organisations, we must address the key contributing human factors. 

Integrating measures to enhance training, minimise fatigue, improve ergonomics, and develop and maintain a strong safety culture is essential. 

Training is a fundamental component, particularly in enhancing situational awareness and route knowledge. Drivers must be fully familiar with their routes, including the locations of signals and potential hazards, and trained to recognise the importance of maintaining attention in varying conditions so they can handle both routine and emergency situations with confidence. This can help to reduce the likelihood of errors caused by misinterpretation of signals or poor decision-making. Simulated training that replicates rare but high-risk situations can further reinforce these skills, ensuring drivers and OCC staff are adequately prepared for any eventuality.

Fatigue remains one of the most significant contributors to SPAD events. Long shifts, irregular hours, and insufficient rest periods contribute to decreased alertness, which impairs the ability to respond to signals. Scheduling should account for circadian rhythms to ensure that drivers are operating when they are most alert and fatigue management strategies, such as monitoring systems that track rest periods can help prevent excessive fatigue from impacting performance.

A safety-focused culture is perhaps the most critical factor in preventing SPADs. A workplace with a strong emphasis on safety and proactive risk management creates an environment where employees are encouraged to report hazards, participate in safety initiatives, and adhere to best practices. If we encourage open communication and a culture of continuous improvement, where near misses are treated as learning opportunities rather than failures, individual organisations and the industry as a whole can effectively move forward. 

Ensuring that Standard Operating Procedures are in place, regularly reviewed and updated, and that all employees are aligned with their requirements can significantly reduce the occurrence of SPADs. A safety culture that values vigilance and encourages reporting of potential risks helps mitigate human errors and ensures that safety remains a top priority.

In conclusion, to effectively reduce SPADs we must adopt a holistic approach that addresses human factors through enhanced training, better scheduling, ergonomic and technological improvements, all integrated within a robust safety culture.

Although fictional, Linda, Augustine, Brian, Fatima, Charlie, Bal and Elena are much more confident in their roles and feel more valued by their employers. Most of all, their personal and company risk profile is much improved!

If you like what you've read, and you would like Transcity to help you develop SPAD reduction initiatives, get in touch and we can discuss your requirements.