Study Participants Drove at Lower Speed, Used Larger Following Gaps, and Reduced Steering Variability When Using Adaptive Cruise Control.

Human Factors Study of Driver Performance With Adaptive Cruise Control on a Northern Virginia Highway.

Date Posted
02/21/2021
Identifier
2021-B01530
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The Effects of Vehicle Automation on Driver Engagement: The Case of Adaptive Cruise Control and Mind Wandering

Summary Information

In recent years, vehicle manufacturers have introduced low level automation features. One such feature, adaptive cruise control (ACC), aims to reduce driver stress and workload by providing longitudinal control. A vehicle equipped with ACC can maintain speed, or adjust speed to keep a following gap if a vehicle ahead is detected by on-board sensors. 

Despite potential for improved safety from ACC, research has not reached a clear conclusion on overall impacts of ACC. While ACC may improve safety by smoothing driving behavior, it may give drivers a false sense of security and lead to “mind wandering” which could increase distracted and/or unsafe driving behaviors.

Methodology

To assess the safety of ACC and the rate of “mind wandering” when using ACC, a research team from FHWA's Turner-Fairbank Highway Research Center tested driver behavior using ACC systems under real-world conditions.

To conduct the study, the team recruited 48 licensed drivers in Northern Virginia. Drivers were assigned to drive a pre-selected 28-mile route on a major highway with and without ACC. The drivers drove under both conditions in a counterbalanced order, while researchers either drove a lead vehicle to be followed, or provided instructions from the back seat.  Physiological measures of heart rate and electrodermal activity (EDA), which are sensitive to levels of effort exerted while driving, were recorded. Additionally, during the test, drivers had to periodically respond to auditory prompts to measure their mental alertness.

Findings

In this study, the research team found:

  • ACC use by participants was associated with decreased speed, longer following gaps, and reduced steering variability compared to manual driving.
  • Mind-wandering rates while using ACC were not higher than those during manual driving.

The researchers also noted that most participants were unfamiliar with ACC prior to joining the study. Behavior of drivers more familiar with ACC may vary from these findings, and further research is needed to assess long-term impacts.

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