By Michael Davis
In commercial motor vehicle fleets, single vehicle run-off-the-road crashes and overturn crashes continue to challenge safety professionals and risk managers. Rollovers and run-off-the-road events account for a small number of all crashes, but contribute to disproportionate costs for property damage and driver injuries.
Fatigue is frequently cited in many accident investigation reports as a contributing factor in vehicle crashes, often due to lack of rest stops or inadequate sleep. The use of cruise control may be adding to the effects of driver fatigue resulting in reduced vehicle control.
Situational Awareness While Using Cruise Control
Independent studies in the USA and France evaluated the impact of the use of cruise control on driving behaviors. The VINCI Autoroutes Foundation in France, in conjunction with the University of Strasbourg, evaluated the effect of conventional cruise control on driver behaviors. The Federal Highway Administration (FHWA) in the U.S. conducted a human factors study on the use of adaptive cruise control. These studies concluded that the use of these types of cruise control systems significantly increased reaction times and decreased situational awareness relating to five factors shown below.
- Delayed perception of an event
- Delayed processing and interpreting of the event
- Delayed selection of the response
- Delayed decision to take action
- Delayed initiation of the response
Conventional Cruise Control
The original design of conventional cruise control systems provided the driver with the ability to maintain a static speed for the vehicle under all operating conditions up to the vehicle’s capabilities. The driver must intervene when road, traffic or weather conditions change and determine when it is safe to use or disengage the system.
Conventional cruise control systems have been in place on commercial motor vehicles for more than 40 years, and during this time, governments and public safety organizations have continued to investigate the risks and benefits of using these systems.
Adaptive Cruise Control
The next generation of cruise control is the “adaptive cruise control,” which, under normal operating conditions, can slow the vehicle or warn the driver of an encroachment into the space cushion ahead. This system provides one level of warning; however, the driver must still decide when conditions change for the road, traffic or weather and determine when it is safe to use the system.
The FHWA’s “Human Factors Analysis” study in 2013 evaluated the effects of using the more advanced type of cruise control—adaptive cruise control—on reaction time and situational awareness when driving. Adaptive cruise control was expected to enable drivers to spend more time watching for driving hazards; however, the study concluded that situational awareness and rapid response deteriorated due to drivers taking on additional non-driving related tasks inside the vehicle.
Effects of Conventional Cruise Control on Safe Driving Behaviors
The VINCI Autoroutes Foundation, in conjunction with the neurocognitive and neurophysiological research team at the University of Strasbourg in Strasbourg, France, conducted research involving 90 drivers. The study included an equal mix of men and women in three age groups to determine how the use of conventional cruise control affected safe driving behaviors in high-risk traffic as well as routine driving conditions. Some of the key measures used to evaluate driver performance included:
- EEG brain wave measurements to determine fatigue and level of alertness/consciousness
- Reaction time to emergency conditions
- Vehicle stopping distances
- Ability to maintain a space cushion
- Ability to maintain lane position
- Self-assessment of fatigue/alertness
The tests were performed with and without cruise control activated and included multiple scenarios such as an accident ahead, toll booth, overtaking, lane changes, construction and radar traps.
In all cases, the study found that driver performance and situational awareness were reduced, resulting in an increased response time when deactivating cruise control compared to drivers in full manual control of vehicle speed.
The study concluded that drivers had:
- Reduced alertness after just 30 minutes of cruise control use—a 25% increase in fatigue
- Reduced eye movement checking mirrors, instruments and roadway
- Reduced control over vehicle direction, resulting in a 33% increase in steering corrections for lane wandering
- Longer reaction times
- An increase in stopping distances of an average 131 feet while traveling at highway speeds
- Performed lane changes with at least 10% less cushion, on average
- Reduced ability to merge into traffic after passing due to continued engagement of cruise control
- Spent more time in the passing lane
Vehicle Crash Rate
For drivers using cruise control, there is an increased risk of fatigue, reduced alertness and delay in hazard recognition, which can lead to driving errors and the following types of crashes:
- Run-off-the-road crashes due to increased lane wandering. Narrow roads increase the risk.
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