The Automotive Collision Avoidance Systems (ACAS) Development Program was formed to further investigate collision warning technologies. The program was originally set up to run for two years but several unexpected delays in simulator development caused the program to be extended for almost one extra year. Therefore, it turned into a three year program, with activities beginning in January 1995 and ending in October 1997. The main objective of the program, to provide a focused approach to accelerate the commercial availability of a portfolio of select high-value key fundamental collision warning countermeasure technologies/systems, was largely accomplished. Progress was made in improved manufacturing processes and accelerated technology development activities. As a result of this program, the gap between R&D and the deployment of new technology in the real world of driver-vehicle-highway systems was substantially bridged. As a matter of fact, this program provided a great deal of new knowledge concerning the influence of new technological capabilities on pertinent aspects of the driving process.
The program activities were accomplished through a cooperative arrangement between the U.S. Government and the program consortium, whose membership is comprised of both industry and academic participants. Financial support for this Program was provided by both the U.S. Government and program consortium members. The U.S. Government financially sponsored this activity through the Defense Advanced Research Project Agency (DARPA), in accordance with the goals of the Technology Reinvestment Program (TRP). The U.S. Government also actively participated in the ACAS Program activities, through NHTSA, which administered the ACAS Program on behalf of the U.S. Government.
The ACAS Program has laid a solid foundation towards 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. Performance requirements of the major components of the CW system, such as long range forward-looking detection sensors (radar or optical, short range side and rear detection sensors, and a lane detection vision-based were investigated. Finally, the effectiveness of a variety of warning cues were also studied. The results of this program have generated new insights for how the CW system should be configured and deployed.
The results demonstrated during this program have been broad, varied, significant, and very encouraging. For example, 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 a FMCW 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 matured as evidenced by the dramatic reduction of false alarms and missed detections. Besides the conventional Path algorithm, a new approach, Scene Tracking, was investigated, producing initial promising results. All MMIC radar transceivers were demonstrated with good system performance in numerous "over the road" tests, the design repeatability was demonstrated by multiple successful 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 limited test track studies. Several human factors studies were conducted either through use of a simulator or in actual driving to determine the best visual and auditory warnings for an effective collision warning (CW) system.
Although substantial gains in knowledge of the CW systems was achieved during the program, there is more work yet to be done. System performance to cost trade-offs is a never ending battle. The real world traffic environment is so varied that it is extremely difficult to make the system free of false alarms. In the future, the system development should take advantage of sensor fusion to increase its robustness. There is also the need to carry limited field operational tests to gain a more thorough understanding of the requirements, functions and societal impact of this technology. Because of the safety impact, any potential adverse operational and safety-related issues should be identified, analyzed, and addressed while the technology is still in the early stages of product development. This is possible only in real world driving situations.