The majority of reporters that come through to CIRAS are shift-workers. They are the drivers, maintenance workers, track workers and other staff who keep public transport running.

It is not surprising that they often report feeling fatigued - long shifts, shift design, shift rotations and rest periods play a role here. All these factors are worthy of being reported if they affect operational safety.

The education shift-workers receive on managing fatigue may vary from company to company. Could some employers be doing more in this respect?

Shift-workers are more likely than nine-to-five workers to build up a sleep debt.

In fact, research shows that shift-workers who sleep in the daytime will experience lower quality sleep, typically sleeping for a third less than they would at night.

What tends to happen is that they wake up spontaneously after fewer hours of sleep.

In these circumstances, strategic napping can play a positive role in restoring energy.

Even after 40 hours of sleep deprivation, a two-hour nap can maintain performance at 70 per cent of well-rested levels (please note that we are not in any way suggesting you deprive yourself of sleep for 40 hours!).

It is important to realise that taking naps can assist in helping shift-workers perform adequately in sleep-deprived circumstances.

Tips for strategic napping

1. Create the right environment This may be easier to arrange at home than it is during working hours, you will need somewhere dark and comfortable. If lighting and noise prove to be an issue, sleep masks or foam ear plugs may be able to control the effects. For a good napping experience, minimise any distractions.

2. Time your naps appropriately Night-time naps are best taken between 1:00am and 6:00am. Daytime naps should ideally be taken between 2:00pm and 4:00pm. In both cases, these times coincide with natural dips in alertness, making a sleep-like quality easier to maintain.

3. Take your naps early on The longer we are awake, the more the effects of fatigue will affect us. If you wake up at 6.00am, and start a shift at 10:00pm, you will have been awake for 16 hours before your shift starts. If your shift is eight hours long, you will have been awake for 24 hours. In this case, it would be smart to take a two-hour nap at 2:00pm. The nap will harmonise better with your circadian rhythms. By the time you start your shift, you will have been awake for only six hours.

4. Make naps as long as possible Just as for sleep, the longer the better. Seven hours sleep will trump four hours sleep every time and a 20 minute nap will be more effective than a 10 minute one.

5. For longer naps, choose between a 45 minute or two hour nap After 45 minutes, the average person will fall from light into deep sleep, which is much more difficult to wake up from. That post-nap grogginess (sleep inertia) can be avoided if a 45 minute nap is cut off then. After 100 minutes, most people will be cycling out of the deep sleep phase, so waking up 20 minutes later at the end of a two hour nap is easier.

Further information

CIRAS works closely with our members to help share good practice to tackle this issue. Many other factors, such as good diet and exercise, are known to have an impact on fatigue levels.

Watch fatigue video here.