In-vehicle detection and warning devices

Several related concepts ‘Driver Vigilance Monitoring’, ‘Drowsiness Detection Systems’, ‘Fatigue Monitoring Systems’ refer to in-vehicle systems that monitor driver and/or vehicle behaviour. These systems monitor the performance of the driver, and provide alerts or stimulation if the driver seems to be impaired.

Driver and vehicle monitoring systems may monitor both driver and vehicle behaviour. Information can be gathered from driver input and control of the vehicles lateral position and speed, such as acceleration, steering wheel movement and lane position. Likewise, user behaviour such as eye movement, facial feature movement, brain waves (EEG) and steering wheel grip may all be monitored.

Estimations of the approximate reductions expected with lane driver monitoring systems in Germany (assuming 70% penetration of the passenger vehicle fleet) were reported by eSafety Forum [30]. It was expected that 50% of fatigue-related crashes would be affected, leading to a 35% reduction in these crashes. This would equate to a 2.9% reduction in all crashes.

Fatigue warning systems (FWS) have been proposed as specific countermeasures to reduce collisions associated with driver fatigue. These devices employ a variety of techniques for detecting driver drowsiness while operating a vehicle and signal a driver when critical drowsiness levels are reached. However, the detection of driver fatigue using valid, unobtrusive, and objective measures remains a significant challenge. Detection techniques may use lane departure, steering wheel activity, ocular or facial characteristics.

Several authors point out that fatigue warning systems may result in driver behavioural adaptation [98]. A possible negative effect of in-car warning systems may be that driver’s use them to stay awake and drive for longer periods rather than stopping and have a nap; i.e. risk compensation by relying too much on the safety system.

This was confirmed by a study of Vincent, Noy & Laing [107]. They evaluated a fatigue warning system that measured ocular and face monitoring, vehicle speed, steering position and lane position. They found the users of the system did not take more or longer breaks, and did not show different fatigue levels to controls. Drivers generally ignored the FWS signals received. The physical aspect of the warning signals used in the study had no impact on driver fatigue levels. Voluntary rest stops, lasting on average 30 minutes, only had a minor impact on decreasing driver fatigue with short-lived effects. The authors concluded that voluntary breaks were ineffective in substantially counteracting the effects of fatigue associated with prolonged night time driving. Whereas normally rested drivers may successfully use breaks to prevent or postpone fatigue during a daytime drive [91], the use of breaks seems less successful in reducing fatigue resulting from prolonged nigh time driving and associated sleep loss.