Fatigue monitoring systems explained

Fatigue monitoring systems were first seen last decade and are now becoming more common in mainstream passenger cars. They're quite often found packaged with other driver assistance technologies and are also known as driver alert systems or driver drowsiness monitors.

Tired and fatigued drivers display certain driving behaviour as their ability to control a vehicle safely becomes impaired. Fatigue monitoring systems keep an eye on the vehicle and driver behaviour to identify any signs that the driver is losing concentration to the point where safety is being compromised.

When the system decides it's time to intervene the driver is alerted to the concern through a visual and audible warning. Typically, the first warning displays a message in the instrument display accompanied by a chime. As you would expect, if the message is ignored and erratic driving continues the warnings become more frequent, demanding the driver take the appropriate action. Whenever the vehicle has stopped with the driver's door open and engine restarted the fatigue monitoring system will reset.

Coincidentally, such systems, like Attention Assist in the new Mercedes S-Class, are beginning to trickle down to more affordable models and budget brands - just as the world's car companies are contemplating level five autonomy as a reality in the near future. This new technology would make fatigue detection redundant.

There's no doubt that driving while tired or fatigued is fraught with danger. Over the years numerous studies have proven the increased risk that comes with the slowed reactions of drowsy drivers and that a large number of serious accidents occur in the early hours of the morning when drivers are less alert.

A fatigue monitoring system acts like a co-driver by making sure the driver's attention level doesn't slip. It points out the danger that an overly tired driver doesn't necessarily notice.

As with other driver assist features, each manufacturer seems to have their own approach to the technology but they all share the same basic philosophy.

Fatigue monitoring systems are constantly scrutinising the driver's behaviour in an attempt to identify unnecessary actions such as a jerky steering input or fluctuating speed. The system "learns" the driver's typical behaviour in the early part of a journey, making the assumption that the driver is fully alert. As the journey time progresses the behaviour is compared to the early data. If there is a large discrepancy the driver alert functions are triggered.

It's also common for the system to piggyback off the data produced by the lane departure warning system's forward facing camera. The position of the car in the road lane is constantly monitored throughout the journey. But instead of monitoring whether the vehicle is leaving its lane the system actually compares the movement of the car in the lane compared to data collected at the start of the journey. In particular, the system is looking for increased levels of drifting within the lane, which is a typical trait of a drowsy driver.

As technology progresses so do fatigue monitoring techniques. Some manufacturers are now implementing systems which analyse the driver's face and head movements while looking for tell-tale signs of tiredness such as blinking, nodding and even how often the driver changes the direction of their eyes.