3.1 Collision Avoidance Systems

To improve the ability of drivers to avoid accidents, collision avoidance systems continue to be tested and deployed. A number of different vehicle-based technologies are under development:

• Intersection collision warning systems are designed to detect and warn drivers of approaching traffic and potential right-of-way violations at intersections.
• Obstacle detection systems use vehicle-mounted sensors to detect obstructions, such as other vehicles, road debris, or animals in a vehicle's path or projected path and alert the driver.
• Lane change warning systems have been deployed to alert bus and truck drivers of vehicles or other obstructions in adjacent lanes when the driver prepares to change lanes.
• Lane departure warning systems warn drivers that their vehicle is unintentionally drifting out of the lane.
• Rollover warning systems notify drivers when they are traveling too fast for an approaching curve, given their vehicles' operating characteristics.
• Road departure warning systems warn drivers that their vehicle is about to leave the roadway, whether they are approaching a curve too fast, or about to drift off the road on a straight roadway segment.
• Forward collision warning systems, often known as rear end collision avoidance systems, warn drivers that they are in a conflict situation with a lead vehicle. These conflicts can arise when the lead vehicle is stopped, slowing, or traveling at a constant speed.
• Rear impact warning systems warn the following vehicle driver that they are in conflict with the lead vehicle. The warning can be presented by the lead vehicle or transmitted to an in-vehicle warning system in the following vehicle.

Table 3.1.1 summarizes the classification of benefits and costs under collision avoidance systems.

While most collision avoidance systems are still in the research, prototype, and testing phases, some (e.g., forward collision warning and lane control) have begun to emerge in mainstream markets. Cost data are not readily available for collision warning systems in the early development stages or even for those systems in the commercial market. Much of the collision avoidance system cost data in reports and studies is based on estimates and/or market analysis of the public's willingness to pay for a specific in-vehicle feature. Also, some of these features are available as factory-installed options, as standard items included in the base cost of a vehicle, or as a component of an upgrade package. Hence, this section contains few examples of system cost data.

Table 3.1.1 provides information on the benefits and costs of collision avoidance systems. An assessment of the impact of these systems is indicated by using the symbols in the Impact Legend at the bottom of each page.

Table 3.1.1 – Benefits and Costs of Collision Avoidance Systems

Intersection Collision Warning

Benefits
No data to report.
Costs
Unit Costs Database	Commercial Vehicle On-Board subsystem Vehicle On-Board subsystem	See Appendix A
System Cost	No data to report.

Obstacle Detection

Benefits
Goal Area	# of Studies	Impact	Example
Safety	1	?	A transport company in St. Nicholas, Quebec, Canada, was able to reduce at-fault accidents by 33.8% in the first year after the installation of a radar-based collision warning system. The system included a forward-looking sensor and a side sensor to warn drivers of obstacles in blind spots.[161]
Costs
Unit Costs Database	Commercial Vehicle On-Board subsystem Vehicle On-Board subsystem		See Appendix A
System Cost	The Federal Transit Administration (FTA), Port Authority of Allegheny County (Pittsburgh, Pennsylvania), and Carnegie Mellon University's Robotics Institute tested a collision avoidance system on 100 buses to warn bus drivers of obstacles in blind spots.[25]		Cost to equip each bus with 12 side-mounted ultrasonic sensors and an on-board computer: $2,600 (approx.) (2001)

Lane Change Assistance

Benefits
Goal Area	# of Studies	Impact	Example
Safety	2	?	A study conducted by NHTSA indicated a lane change/merge crash avoidance system would be effective in 37% of crashes.[24]
Costs
Unit Costs Database	Commercial Vehicle On-Board subsystem Vehicle On-Board subsystem		See Appendix A
System Cost	A collision warning system that uses radar technology can reduce sideswipes during lane changes and right turns.[162]		Average cost for a collision warning system with forward-looking and sidesensor: $2,500

Road Departure Warning

Benefits
Goal Area	# of Studies	Impact	Example
Safety	2	?	A study conducted by NHTSA indicated a road-departure countermeasure system would be effective in 24% of crashes.[24]
Costs
Unit Costs Database	Commercial Vehicle On-Board subsystem Vehicle On-Board subsystem		See Appendix A
System Cost	No data to report.

Forward Collision Warning

Benefits
Goal Area	# of Studies	Impact	Example
Safety	3	?	A NHTSA modeling study indicated collision warning systems would be effective in 42% of rear-end crash situations where the lead vehicle was decelerating, and effective in 75% of rear-end crashes where the lead vehicle was not moving. Overall, collision warning systems would be 51% effective.[24]
Costs
Unit Costs Database	Commercial Vehicle On-Board subsystem Vehicle On-Board subsystem		See Appendix A
System Cost	A Florida-based trucking company has installed a collision warning system to reduce the number of rear-end incidents. Adaptive cruise control can be added to further reduce rear-end collisions.[162, 163]		Average cost for a collision warning system with forward-looking and sidesensor: $2,500 Adaptive cruise control: $350–$400 extra

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