ACAS Program
Final Report -- May 10, 1998
Tremendous progress has been made since the 1960's with regard to vehicle safety. Improvements in passive safety features such as seat belts, air bags, crash zones, and lighting have dramatically reduced the rate of crashes, injuries and fatalities. For example, the fatality rate per hundred million vehicle miles traveled has fallen from 5.5 to 1.7 in the period from the mid-1960s to 1994. However, in spite of these impressive improvements, each year in the United States, motor vehicle crashes still account for a staggering 40,000 deaths, more than three million injuries, and over $130 billion in financial losses. Significant further gains in reducing crash costs will prove more difficult to achieve by proceeding with the current passive safety technologies alone. Consequently, there is merit to investigation of other potential technologies in an attempt to reduce the severity of crashes or even complete mitigation of collisions.
The introduction of automotive Collision Warning Systems potentially represents the next significant leap in vehicle safety technology. Such systems attempt to actively warn drivers of an impending collision event, allowing the driver adequate time to take appropriate corrective actions to mitigate, or completely avoid, the event. Crash statistics and numerical analysis strongly suggest that such collision warning systems will be effective. Crash data collected by the U.S. National Highway Traffic Safety Administration (NHTSA) show that approximately 88% of rear-end collisions are caused by driver inattention and following too closely. These types of crashes could derive a beneficial influence from such systems. In fact, NHTSA countermeasure effectiveness modeling predicts that “head-way detection systems can theoretically prevent 37% to 74% of all police reported rear-end crashes.” Clearly, the introduction of collision warning systems could result in the dramatic reduction of crash fatalities, injuries, and property damage.
With this as an impetus, the Automotive Collision Avoidance Systems (ACAS) Program was launched. It was originally set up to be a two-year program with activities beginning January 1995. The activities were carried out by a consortium made up of government agencies as well as, industrial and academic participants. The main objective of the Consortium is to provide a focused approach to accelerate the development of active collision avoidance systems. The nine-member consortium is comprised of recognized leaders in their respective field of expertise in the technology, manufacturing and marketing of collision avoidance products. It was believed that through the formation of this Consortium, U.S. competitiveness in the automotive electronics industry would be maintained and further enhanced. Furthermore, once systems are deployed, the expansion of employment, sales, and export of U.S. technologies will result.
The ACAS Program envisions the implementation of a comprehensive collision warning system, which is capable of detecting and warning the driver of potential hazard conditions in the forward, side, and rear regions of the vehicle. The system would use: (1) long range radar or optical sensors to detect potential hazards in front of the vehicle, (2) short range sensors to warn the driver of nearby objects when changing traffic lanes or backing up, and (3) a lane detection system to alert the driver when the vehicle deviates from the intended traffic lane. The program effort is focused on providing warnings to the driver, rather than taking active control of the vehicle.
For such a system to gain acceptance by consumers, it must be reasonably priced, possess sufficient and effective functionality, and provide highly reliable performance. In order to achieve these goals, the ACAS Program has relied heavily on the principles of system engineering as a framework to guide the highly focused design effort. The activities of the program can be grouped into three main themes. The first theme is the refinement of existing or partially developed collision warning/avoidance technologies/systems in order to achieve further cost reductions by improving the manufacturing processes. The second theme is the accelerated development of other promising but immature technologies/systems that are essential for collision warning/avoidance. The third theme is the application of human factors engineering in the design and implementation of collision warning systems. A collision warning system will be of little use to the automotive consumer, if the driver can not effectively be made aware of potentially hazardous roadway situations. The set of warning cues that is provided must not be annoying, intrusive, or confusing.
This report summarizes the major technical accomplishments during the ACAS Program (January 1995 – October 1997). The accelerated development of strategic technologies/systems that are the essential building blocks for a fully integrated comprehensive collision warning system, has mainly focused on the following three areas: (a) sensors (i.e., forward-looking radars and lasers, side detection radars, and lane tracking vision), (b) systems (i.e., path estimation, in-path target selection, and threat assessment), and (c) human factors (i.e., driver-vehicle interfaces, and understanding the effects of warning cues on drivers). The results demonstrated during this program have been broad, varied, significant, and very encouraging. Some of these achievements are discussed below.
A varied and extensive analysis of crash data has been carried out in order to focus the system requirements of an integrated collision warning system. Several demonstration vehicles, equipped with the rudimentary capabilities of a forward collision warning system, have been designed, developed, constructed, and successfully demonstrated. These vehicles demonstrated the viability of the baseline system architecture. Additionally, remarkable progress has been achieved in the individual development of strategic technologies/systems/components, in such areas as: active sensors (i.e., radar, laser and vision), algorithm/software development (i.e., collision warning processing components), and human factors.
For instance, the linearity of FMCW (Frequency Modulated Continuous Wave) radar has been improved by an order of magnitude, while the development unit cost has been reduced by a factor of three. The production unit cost is projected to be reduced by a factor of five. A significant improvement in sensor reliability was also achieved (zero field returns versus 20% prior to the ACAS program). The collision warning processing algorithm suite has matured as evidenced by the dramatic reduction of false alarms and missed detections. Besides the conventional Path algorithm, a new approach, Scene Tracking, has been investigated and has yielded promising initial results. All MMIC (Microwave Monolithic Integrated Circuit) radar transceivers were demonstrated with good system performance via road testing, the design repeatability was demonstrated via multiple wafer runs, and the reliability of the design was verified through environmental tests. On the human factors front, a wide field of view (4.5 x 3.0 degrees) Head-Up Display (HUD) was developed with high brightness and excellent image quality. It was used for simulator studies as well as for actual vehicle installations. Several human factors studies were conducted in a simulator and in actual driving situations, to determine the best visual and auditory warnings for an effective collision warning system.
Now that the primary objective of the ACAS Program has largely been achieved, the next logical technical progression of the product development would be the upward integration of these ACAS-developed essential building blocks to form a complete seamless vehicle system which can be evaluated through a field operational test program. This test program, if carried out, will provide an ideal opportunity for the Government, industry, and Intelligent Transportation System (ITS) community to gain a more thorough understanding of the requirements, functions and societal impact of this technology. Additionally, any potentially adverse operational and safety-related issues could be identified, analyzed, and addressed while the technology is still in the early stages of product development. This program has the opportunity to make a positive impact on automotive safety through the accelerated development and early deployment of effective advanced safety technologies.