Forward collision warning systems with adaptive cruise control warn drivers of a potential collision risk and assist in maintaining a safe following distance between their vehicle and the vehicle directly ahead of them.
Collision Warning Systems (CWS) are in-vehicle electronic systems that monitor the roadway in front of the vehicle and warn a driver when a potential collision risk exists if another vehicle or object is in its lane. The forward looking, radar-based or monocular vision-based CWS systems use algorithms to interpret transmitted and received radar signals in order to determine distance, azimuth location, and relative speed between the host vehicle equipped with the CWS and the vehicle or object in its projected path. CWS do not take any automatic action to avoid a collision or to control the vehicle; therefore, drivers remain responsible for driving safely.
Adaptive Cruise Control (ACC)
Adaptive Cruise Control (ACC) systems are in-vehicle electronic systems that can be integrated with CWS and automatically maintain a minimum following interval to a lead vehicle in the same lane. When there is no vehicle ahead of the host vehicle, the ACC system operates like conventional cruise control by maintaining the speed set by the driver. The driver can set and adjust his following interval. Although ACC systems automatically alter the vehicle’s speed by controlling the engine throttle, and if available, engine brake and automatic transmission, the system may not sufficiently decelerate the vehicle in all circumstances to avoid a crash. Hence, the driver remains responsible for the safe operation of the vehicle by steering and applying the service brakes to avoid a crash.
Some ACC systems use radar and video sensing in a complimentary manner to provide a wider field of view to distinguish between relevant in-path vehicles and objects and non-relevant vehicles and objects, such as guardrails, bridges, and other roadside structures that are not in the vehicle’s immediate path. ACC systems can also be integrated with information management systems, which can record and monitor events such as, engine idle, driving time, non-driving time, vehicle speed, hard braking events, and following time.
Under certain conditions, the detection range of these systems may be limited. Depending on the technology used, traversing sharp curves may cause limited coverage, where the lead vehicle may no longer be in the range of the host vehicle’s sensor coverage area. When this occurs, CWS may not redetect the lead vehicle until the host vehicle enters the curve. At the same time, the ACC system will use conventional cruise control by maintaining the current set speed until detection of the lead vehicle resumes. Upon redetection of the lead vehicle, the ACC system will revert back to the previously set following interval. Furthermore, CWS may produce false positive indications when the host vehicle is on a roadway with major changes in elevation. False alarms can also occur from other roadway features and objects.
Rear-end crashes involving large trucks can be particularly severe, since a significant percentage of these crashes involve three or more vehicles. CWS can reduce the risk of rear-end crashes by identifying fast-closing situations and providing the driver with additional time to decelerate the vehicle. CWS can also reduce the risk of striking a stationary object that is in the vehicle’s travel lane by warning the driver of the presence of the object, and allowing additional time for the driver to appropriately maneuver the vehicle to avoid the object. ACC systems function to maintain a following interval behind another vehicle, thereby providing more time for a driver to avoid a rear-end collision. CWS may also include headway monitoring capabilities by notifying the driver of inappropriate distance keeping, which in itself reduces the chance of rear-end collisions.
Operations and Benefits
The movement of goods and products by truck is conducted on all types of roads, at all hours of the day, and in all types of driving conditions. A driver may encounter several types of roadways and situations where CWS and ACC systems can help prevent rear-end crashes and forward impact crashes when objects are in the travel lane. These systems may also reduce crash impact speed and severity.
The domino affect of a rear-end collision involving a large truck can cause multiple injuries, possible loss of life, and extensive vehicle and cargo damage. As a result, many types of fleets could benefit from using CWS with ACC. Use of CWS may be most promising for trucks with high mileage accumulated over their operational life or those which operate under conditions that present driving challenges such as nighttime or limited visibility due to weather. In addition, CWS can operate at any vehicle speed, but ACC systems only operate above a specified minimum vehicle speed, which typically limits their use to roadways where drivers travel at or above this minimum speed in accordance with the posted speed limits. The benefits of these systems to specific fleets may be determined by the amount of time the fleet’s vehicles operate on these roadways.
The installed cost of the CWS range from about $1,000 to $3,000 per vehicle depending on the features associated with the unit and the amount of units purchased. The ACC system costs approximately $350 to $400 per unit when integrated with the CWS.
Eaton Vorad Corporation
1111 SUPERIOR AVE
Delphi Electronics and Safety
P.O. Box 9005
Kokomo, IN 46904
Ph: (765) 451-5001
2000 Town Center, Suite 1900
Southfield, MI 48075
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