Delivering safe and effective air traffic control (ATC) is all about people. As the UK’s leading provider of ATC, NATS handles 2.3 million flights carrying 250 million passengers in UK airspace each year. Human performance must be maximised to ensure that those responsible for safety are operating at their very best.

ATC is a 24-hour, 365-day operation. Individual controllers make thousands of important decisions every day to ensure aircraft are safely separated and routed efficiently. The role relies on quick thinking and clear communication, and it is crucial that controllers remain at their peak performance at all times, especially in the middle of the night when their bodies are telling them that they should be asleep.

Fatigue is taken very seriously at NATS. It is caused by prolonged mental or physical exertion, and can affect people’s performance and impair their mental alertness. Fatigue is a normal physiological state, like hunger and thirst, and it cannot be suppressed. It is a signal from our body alerting us that we need to rest.

Studies have shown that fatigue has an effect on human performance similar to that of alcohol. For example, being awake for 17 hours continuously in a 24-hour period is equivalent to a blood-alcohol content of 0.05% – that is the equivalent of two glasses of wine, and is over the drink/drive limit for many countries.

Three to watch

There are three types of fatigue: mental, visual and physical. Mental fatigue results in feelings of weariness, reduced alertness, slower decision-making, poorer judgement and impaired ability to detect errors. Visual fatigue results in watering and reddening of the eyes, difficulty in focussing, reduced speed of perception, an increased likelihood to misread information and poorer vigilance. Physical fatigue results in aching muscles and the need to rest.

For people with engineering, maintenance or driving roles, for example, managing physical fatigue is a high priority, but for an air traffic controller who is processing and communicating information while working in front of a radar screen or looking out of an airport control tower window, managing mental and visual fatigue is crucial.

With this in mind, it is essential to take steps to prevent controllers being adversely affected by it.

Fatigue can have a significant impact on a controller’s ability to make timely, accurate and correct decisions – so it is crucial that all air navigation service providers (ANSPs) take steps to minimise the risk of fatigue affecting controllers and their operations. It is a worldwide issue.

The International Civil Aviation Organisation (ICAO) recognises the extreme importance of managing fatigue risk across the aviation industry. For many years, strict regulations have been in place limiting the number of hours pilots are allowed to fly. Similar regulations are being introduced in 2020 that will govern the working hours of air traffic controllers.

ICAO has clearly stated that the management of fatigue is a joint responsibility between the regulator, the ANSP and the controller. Regulators must provide a regulatory framework that enables adequate fatigue management and ensures that the ANSP is effectively managing its fatigue-related risks.

ANSPs must implement work schedules that enable controllers to perform their duties safely, structured in such a way as to minimise the effects of fatigue. This includes the provision of a working environment fitted with appropriate lighting and equipment, and maintained at an optimum temperature. Adequate opportunities for rest and sleep must be made available. Fatiguemanagement education programmes and awareness training must be offered to all controllers, and a process must be in place for monitoring and managing it.

Healthy perspective

Controllers have a responsibility to come to work fit for duty and to manage their own levels of fatigue. They have an individual obligation to make appropriate use of non-controlling periods both while on duty and between work periods.

They must report any fatigue issues that they identify. To help fight the effects of fatigue, controllers should keep hydrated, have a healthy diet and maintain their fitness.

To remain alert, controllers should also manage their sleep patterns ensuring that they are well rested before coming to work. While the pressures of family and everyday life can make it difficult to achieve, controllers should try to obtain enough good quality sleep, as this is the prime method of combating fatigue.

NATS has been actively managing fatigue for many years – in line with future ICAO regulations, our policy makes it very clear that the responsibility for managing it lies jointly with the company and with each employee.

From a corporate perspective, NATS operates a forward rotation of shifts covering two mornings then two afternoons and, finally, two nights. This is then followed by a sleep day and three days off. Scientists have shown that a forward rotation of shift helps the body to adapt better to changing working hours than a backward rotation.

NATS’ controllers are subject to the most stringently controlled working hours and rest-break rules in Europe. The period during which a controller stays in position directing aircraft is very closely monitored and must not exceed two hours without a 30-minute responsibility-free break. Responsibility free means that controllers cannot undertake any work activities during their breaks and instead are encouraged to rest, keep hydrated and eat healthily. Those working on the busiest airspace sectors are relieved from duty every 90 minutes to ensure that they remain fully alert.

Indeed, on some sectors where workload is particularly high at times, supervisors will attempt to relieve controllers from their working position after 60 minutes to provide them with additional time to rest and recover.

The working environment is a very important factor in helping personnel stay at the top of their game. The lighting, temperature, seating and workstation layout in our operations rooms are all carefully designed to promote alertness and maximise human performance. A team of humanfactors specialists are fully involved in the design, testing, training and implementation of all major changes to equipment, airspace, procedures and operations room layout.

Monitoring of daily operations is undertaken to identify any problems and to determine where improvements can be made. Keeping controllers at peak human performance is absolutely essential because people really do create safety.

Rest facilities are provided, with the view of allowing controllers to nap or sleep in their rest periods at night so that they will be at the peak of their performance in good time for the early morning rush.

Where traffic demand and staff numbers allow, controllers are able to sleep in dedicated facilities for up to two hours during a night shift. This is to ensure that they are fully rested and ready for the early-morning rush.

Napping is also encouraged. Science has shown that there are positive recuperative effects to be gained from napping for 20 minutes. Facilities are provided close to the operations room for this and ten minutes is provided post nap to allow controllers to fully overcome sleep inertia. They are also encouraged to make use of the sleeping facilities after a night shift. If they have a long drive home from work, this allows them to rest before starting the journey.

Analysis shows that humans are more likely to make mistakes when they have either very high, or very low, workloads. During night shifts when generally there is less traffic to control and hence workload is low, it is very important to keep controllers alert. To achieve this, controllers are located close together in the operations room, and are encouraged to undertake activities that keep them physically and mentally alert, while not being distracted from their primary task of managing traffic.

Danger signs

All NATS controllers are given mandatory fatigue-awareness training every two years. This includes information on the causes and signs of fatigue, and provides controllers with a ‘toolkit’ to help them prevent it affecting their performance. The training also encourages them to develop a lifestyle that takes account of the demands of shift working, and offers suggestions to help them deal with the underlying causes of fatigue at work and in their everyday lives.

NATS operations managers are trained to look for and recognise the signs of fatigue in their staff. Beyond the outward signs associated with tiredness such as yawning, irritability and moodiness, there are also well-documented work-related signs that include a reduction in co-worker interaction or job-related communications, a reduced ability to manage usual workload levels, or an increase in mistakes that require correction. There are also taskperformance signs such as poor vigilance, reduced flexibility and adaptability, increased reaction times, working more slowly to maintain accuracy, and a greater reliance on colleagues.

The measurement of fatigue is undertaken on a regular basis. This uses the internationally recognised Samn- Perelli scale, where individuals rate their level of fatigue on a scale of one to seven. A score of one indicates that the controller is fully alert and wide awake, while seven indicates that they are completely exhausted and unable to function effectively. In any safety-critical role, there should be no scores above five. Collection of this type of data provides assurance that fatigue is being managed effectively by NATS and by individual controllers.

In most cases, fatigue is fully countered by getting good-quality sleep. However, in a small number of cases, there can be medical issues that result in controllers not being able to obtain the amount and quality of sleep that they need. In these cases, NATS’ occupational health service is there to provide medical advice.

So the next time you are nodding-off on a late night flight over the UK, you can rest assured that the controllers handling your flight are wide awake, thinking clearly, and keeping you and your fellow passengers safe.