NTSB Number: SIR-01-01
NTIS Number: PB2001-917003
Adopted May 1, 2001
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In 1999, the most recent year for which data are available, more than 6 million crashes occurred on U.S. highways, killing over 41,000 people and injuring nearly 3.4 million others. Rear-end collisions accounted for almost one-third of these crashes (1.848 million) and 11.8 percent of multivehicle fatal crashes (1,923). Commercial vehicles were involved in 40 percent of these fatal rear-end collisions (770), even though commercial vehicles only comprised 3 percent of vehicles and 7 percent of miles traveled on the Nation's highways. Between 1992 and 1998, the percentage of rear-end collisions involving all vehicles increased by 19 percent. In 1999, 114 fatal crashes in work zones involved rear-end collisions, about 30 percent of the multivehicle fatal work zone crashes. Of these, 71 collisions (62 percent) involved commercial vehicles.
In the past 2 years, the National Transportation Safety Board investigated nine rear-end collisions in which 20 people died and 181 were injured (three accidents involved buses and one accident involved 24 vehicles). Common to all nine accidents was the rear following vehicle driver's degraded perception of traffic conditions ahead. During its investigation of the rear-end collisions, the Safety Board examined the striking vehicles and did not find mechanical defects that would have contributed to the accidents. In each collision, the driver of the striking vehicle tested negative for alcohol or drugs. Some of these collisions occurred because atmospheric conditions, such as sun glare or fog and smoke, interfered with the driver's ability to detect slower moving or stopped traffic ahead. In other accidents, the driver did not notice that traffic had come to a halt due to congestion at work zones or to other accidents. Still others involved drivers who were distracted or fatigued.
Regardless of the individual circumstances, the drivers in these accidents were unable to detect slowed or stopped traffic and to stop their vehicles in time to prevent a rear-end collision. According to a 1992 study by Daimler-Benz, if passenger car drivers have a 0.5-second additional warning time, about 60 percent of rear-end collisions can be prevented. An extra second of warning time can prevent about 90 percent of rear-end collisions.
As the Safety Board reported in 1995 and further discussed at its public hearing, Advanced Safety Technologies for Commercial Vehicle Applications, held August 31 through September 2, 1999, existing technology in the form of Intelligent Transportation Systems (ITS) can prevent rear-end collisions. ITS, capable of alerting drivers to slowed or stopped traffic ahead, have been available for several years but are not in widespread use. The technology to alert drivers to traffic ahead includes adaptive cruise control (ACC), collision warning systems (CWSs), and infrastructure-based congestion warning systems. ACC detects slower moving vehicles ahead and closes the throttle and applies the engine brake to slow the host vehicle to a comparable speed. CWSs detect slower moving vehicles ahead and warn the driver of the host vehicle about the object ahead so the driver can take appropriate action. Infrastructure-based congestion warning systems use variable message signs to give drivers detailed information about the location of traffic queues. In the nine accidents investigated by the Safety Board, one (and sometimes more) of these technologies would have helped alert the drivers to the vehicles ahead, so that they could slow their vehicles, and would have prevented or mitigated the circumstances of the collisions.
The Safety Board addressed implementation of such systems for commercial vehicles in its 1995 special investigation of collision warning technology and recommended that the U.S. Department of Transportation (DOT) sponsor fleet testing of CWSs for trucks. On August 10, 1999, the Board classified the recommendation "Closed-Unacceptable Action" due to inaction by the DOT on testing of the CWS for trucks at that time. (See the "Related Report and Consequent Recommendations" section of this report for further information.)
Because of the lack of progress in deploying rear-end CWSs, the Safety Board addressed the issue at its summer 1999 public hearing focusing on advanced safety technologies for commercial vehicle applications to determine what had been done since its 1995 report. (See "Public Hearing" section of this report for further information.) At the hearing, representatives of Eaton VORAD Technologies, L.L.C. (Eaton VORAD); U.S. Xpress Enterprises, Inc. (U.S. Xpress); Greyhound Lines, Inc. (Greyhound); and the DOT provided information regarding the CWS and the status of various tests and deployments. As became clear during the public hearing, private industry is beginning to deploy vehicle-based safety systems. The CWS and ACC developed by Eaton VORAD are available as an option on trucks produced by all major manufacturers in the United States. Automobile manufacturers in Europe and Japan have begun to offer ACC on their high-end models, and Lexus and Mercedes are doing the same on their 2001 luxury vehicles in the United States.
According to a March 2000 TRW press release, industry analysts predict the market for ACC, CWSs, and headway control will grow from $11 million in 1998 to $2.4 billion in 2010. In 1999, the DOT commenced operational tests of ACC and CWSs for both cars and trucks. Several States also have projects under way to deploy infrastructure-based technology that alerts drivers to the location of the end of the queue in work zones or congested areas.
The work being done by private industry and the Government is encouraging, but the pace of testing and of standards development for all vehicles and of deployment for commercial vehicles is cause for concern, given the increasing number of rear-end collisions and the number of fatalities when commercial vehicles are involved. Therefore, the Safety Board is again addressing subjects related to ITS, both vehicle- and infrastructure-based, for the prevention of rear-end collisions. The Safety Board has explored the issues involved in deploying technological solutions in this special investigation report, which focuses on some of the challenges, including implementation, consumer acceptance, public perception, and training associated with the deployment of such systems.
To the U.S. Department of Transportation:
Complete rulemaking on adaptive cruise control and collision warning system performance standards for new commercial vehicles. At a minimum, these standards should address obstacle detection distance, timing of alerts, and human factors guidelines, such as the mode and type of warning. (H-01-06)
After promulgating performance standards for collision warning systems for commercial vehicles, require that all new commercial vehicles be equipped with a collision warning system. (H-01-07)
Complete rulemaking on adaptive cruise control and collision warning system performance standards for new passenger cars. At a minimum, these standards should address obstacle detection distance, timing of alerts, and human factors guidelines, such as the mode and type of warning. (H-01-08)
To the National Highway Traffic Safety Administration:
Develop and implement, in cooperation with the Federal Highway Administration, the Intelligent Transportation Society of America, and the truck, motorcoach, and automobile manufacturers, a program to inform the public and commercial drivers on the benefits, use, and effectiveness of collision warning systems and adaptive cruise controls. (H-01-09)
To the Federal Highway Administration:
Develop and implement, in cooperation with the National Highway Traffic Safety Administration, Intelligent Transportation Society of America, and the truck, motorcoach, and automobile manufacturers, a program to inform the public and commercial drivers on the benefits, use, and effectiveness of collision warning systems and adaptive cruise control. (H-01-10)
Develop a procedure that States can use to conduct a risk analysis for work zone backups; require, where appropriate, the use of a queue length detection and warning system; and incorporate that procedure for a queue length detection and warning system for work zones in the Manual on Uniform Traffic Control Devices work zone guidelines. (H-01-11)
To the Truck and Motorcoach Manufacturers:
Develop and implement, in cooperation with the National Highway Traffic Safety Administration, the Federal Highway Administration, the Intelligent Transportation Society of America, and automobile manufacturers, a program to inform the public and commercial drivers on the benefits, use, and effectiveness of collision warning systems and adaptive cruise control. (H-01-12)
Develop a training program for operators of commercial vehicles equipped with a collision warning system or adaptive cruise control and provide this training to the vehicle operators. (H-01-13)
To the Automobile Manufacturers:
Develop and implement, in cooperation with the National Highway Traffic Safety Administration, the Federal Highway Administration, the Intelligent Transportation Society of America, and the truck and motorcoach manufacturers, a program to inform the public and commercial drivers on the benefits, use, and effectiveness of collision warning systems and adaptive cruise control. (H-01-14)
To the Intelligent Transportation Society of America:
Develop and implement, in cooperation with the National Highway Traffic Safety Administration, the Federal Highway Administration, and the truck, motorcoach, and automobile manufacturers, a program to inform the public and commercial drivers on the benefits, use, and effectiveness of collision warning systems and adaptive cruise control. (H-01-15)
To the American Trucking Associations, Inc., the Owner-Operator Independent Driver Association, and the National Private Truck Council:
Encourage your members to obtain or provide, or both, training to those drivers who operate collision warning system- or adaptive cruise controlequipped trucks. (H-01-16)
