Approximately 80 percent of the truck drivers surveyed indicated that collision warning systems made them more vigilant, helped them maintain a safer following distance, and increased their reaction time and awareness.
Made Public Date


United States

Evaluation of the Volvo Intelligent Vehicle Initiative Field Operational Test: Final Report - Version 1.3

Summary Information

The U.S. DOT sponsored an independent evaluation of a field operational test (FOT) of three advanced intelligent vehicle safety systems (IVSS): collision warning systems (CWS), adaptive cruise control (ACC), and advanced braking systems (AdvBS).

  • CWS installed on fleet vehicles (tractors) used in-cab visual displays and audible alarms to notify drivers to take corrective action if forward radar sensors detected a potential crash.
  • ACC maintained set headways between tractors and lead vehicles, and was designed to operate as a conventional cruise control system if no lead vehicle was present.
  • AdvBS installed on fleet vehicles used air disc brakes and an electronically controlled braking system to enhance braking performance and reduce stopping distances.

Data acquisition systems (DAS) were used to assess safety impacts "with" and "without" IVSS technologies installed on 100 trucks for 30 months starting in 2001. The following three combinations of IVSS technology were evaluated.

  • CWS
  • ACC + AdvBS
  • CWS + ACC + AdvBS (bundled system)

Impacts on crash rates were estimated based on an analysis of the frequency and severity of rear-end driving conflicts encountered. A driving conflict was defined as a safety-critical situation that had potential to result in a crash if the driver did not react quickly or sufficiently.


Telephone interviews were conducted with 200 drivers in two phases to assess their perceptions and acceptance of system performance. Phase-1 (22 – 27 October 2001) included 117 drivers and focused on driver expectations. Phase-2 (29 March – 6 April 2004) included 87 drivers and focused on driver experiences.
  • Approximately 80 percent of drivers indicated that CWS helped them reduce accident risk because it made them more vigilant, helped them maintain a safer following distance, and increased their reaction time and awareness.
  • Approximately 60 percent indicated that the technology changed their driving habits.
  • Approximately half of the drivers interviewed indicated that the ACC system reduced accident risk by helping to maintain safer distances.
  • Eighteen (18) percent, however, indicated the technology increased risk due to reduced attentiveness and driver control.
  • Approximately 75 percent of drivers believed that AdvBS improved driving safety due to improved braking ability.