Benefit

In Michigan, an evaluation of adaptive cruise control indicated that the technology was effective at reducing risky lane changes in response to slower traffic, but took 0.3 seconds longer than manually controlled vehicles to respond to lead vehicle brake lights.


October 1999
Statewide,Michigan,United States


Summary Information

This study examined the safety, performance, user-acceptance, and deployment of intelligent cruise control (ICC) systems. The findings were based on a field operational test (FOT) conducted by the National Highway Traffic Safety Administration (NHTSA) and the University of Michigan Transportation Research Institute (UMTRI). The FOT involved 108 volunteer test drivers and 10 ICC-equipped Chrysler Concordes. The testing was performed between July 1996 and September 1997, and the results were analyzed by Volpe and SAIC.

The ICC system was designed to automatically maintain a set-time headway using throttle modulation and down shifting (but not braking) at speeds above 25 mi/h (40.3 km/h). When traffic was encountered, the ICC-equipped vehicles automatically adjusted their velocity settings. When vehicles were not in traffic, the ICC system operated like conventional cruise control (CCC).

UMTRI selected participants from a database of 3,000 licensed drivers in Southeast Michigan. 108 drivers from three different age groups (20 to 30; 40 to 50; and 60 to 70 years) were recruited to participate in the evaluation and test drive 10 mid-size passenger cars equipped with ICC. UMTRI staff introduced the ICC vehicle to participants and then demonstrated the system on interstate and state highways. Participants were informed that the cruise control system would operate conventionally during the first week, and then ICC functions would become available.

During the FOT, 24 drivers received vehicles for 5 weeks and 84 drivers received vehicles for 2 weeks. The average participant used the ICC system for 19 hours for a distance of 1,023 miles (1,646 km) at velocities above 25 mi/h. The ICC system was used extensively on freeways, approaching 60 percent usage on trips greater than 15 minutes.

The findings of this study were based on questionnaires given to drivers, and vehicle performance data collected from field trials designed from a surrogate safety analysis framework. The framework criteria evaluated vehicle behavior in terms of following, closing, cruising, or separating activities as a result of cut-ins, lane changes, approaches, and lead vehicle decelerations.

The following list represents a general overview of field trial results:

Driving States and Transitions
  • Freeway Traffic: ICC vehicles spent the least amount of time closing-in on other vehicles
    • ICC vehicles spent 5.1 percent of time closing on lead vehicle
    • CCC vehicles spent 5.2 percent of time closing on lead vehicle
    • Manual vehicles spent 6.8 percent of time closing on lead vehicle
  • Freeway Traffic: ICC vehicles had fewer risky lane changes in response to slower traffic
    • ICC vehicles had a lane-change rate of 8 lane changes per 100 km with 2 percent of the lane-changes resulting in a close closing-in situation
    • CCC vehicles had a lane-change rate of 7 lane changes per 100 km with 7 percent of the lane-changes resulting in a close closing-in situation
    • Manual vehicles had a lane-change rate of 19 lane changes per 100 km with 8 percent of the lane-changes resulting in a close-closing situation
  • Freeway Traffic: ICC and CCC vehicles had fewer occurrences of short headways and high closing rates resulting from cut-ins
    • ICC vehicles had a cut-in rate of 12 cut-ins per 100 km
    • CCC vehicles had a cut-in rate of 12 cut-ins per 100km
    • Manual vehicles had a cut-in rate of 20 cut-ins per 100 km
  • Arterial Traffic: Manual vehicles spent the least amount of time closing-in on other vehicles
    • ICC vehicles spent 8.5 percent of time closing on lead vehicle
    • CCC vehicles spent 6.5 percent of time closing on lead vehicle
    • Manual vehicles spent 4.4 percent of time closing on lead vehicle
Overall Driving Behavior
  • CCC-vehicles had the longest headway time on freeways
    • ICC vehicles averaged 1.9 second headway
    • CCC vehicles averaged 2.2 second headway
    • Manual vehicles averaged 1.7 second headway
  • CCC vehicles had the least velocity variability and likelihood of closings
    • ICC vehicles averaged a standard deviation of 4.4 km per hour (km/h)
    • CCC vehicles averaged a standard deviation of 2.8 km/h
    • Manual vehicles averaged a standard deviation of 11.1 km/hr
  • Manual vehicles had the lowest average vehicle speed as an indicator of potential dangerous closing situations
    • ICC vehicles average speed was 106 km
    • CCC vehicles averaged speed was 110 km/h
    • Manual vehicles averaged speed was 96 km/hr
  • Manual vehicles had the quickest average response time to lead vehicle brake lights
    • ICC vehicles response time was 0.3 seconds longer than Manual vehicle response time
    • CCC vehicle response time was slightly longer than ICC vehicle response time


FINDINGS

The ICC-system performed well during controlled experiments on public roadways. The vehicle sensors were able to detect vehicle targets in the specified field of view, maintain set headways and velocities, and reduced the need for drivers to brake unnecessarily within the ICC control parameters. ICC sensors were able to reliably detect vehicle targets at a maximum distance of 100 meters. However, in severe rain and snow the vehicle sensors had performance problems due to back-scatter.

Overall, evaluators were concerned with the tendency of test drivers to delay intervention and rely on the ICC system to resolve safe driving issues. Overall, field test participants ranked the Manual vehicle the most safe, ICC the next safest, and CCC the least safe.

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Source

Evaluation of Intelligent Cruise Control System. Volume I - Study Results

Author: Koziol, J., et al.

Published By: Federal Highway Administration, U.S. DOT

Prepared by Volpe for the U.S. DOT

Source Date: October 1999

EDL Number: 11843

Other Reference Number: Report No. DOT-VNTSC-NHTSA-98-3

URL: https://rosap.ntl.bts.gov/view/dot/4273

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Goal Areas

Safety

Typical Deployment Locations

Metropolitan Areas

Keywords

intelligent cruise control, ICC, ACC, Intelligent Speed Adaptation, ISA

Benefit ID: 2007-00481