Collision Avoidance System Field Operational Test
8 DRIVER-VEHICLE INTERFACE (Task B5)
The primary objective of the Driver-Vehicle Interface Task is to develop an interface that will convey information from the Adaptive Cruise Control and Forward Collision Warning systems to the vehicle operator in as unambiguous a fashion as possible. For the FCW system, warning cues and presentation methodology must be selected and developed so as to immediately direct the driver's attention to the primary task of evaluating and reacting to the critical crash event, while allowing sufficient time to perform some corrective vehicle control action to either avoid the event or at a minimum to mitigate the crash energy. For the Adaptive Cruise Control system, sufficient information must be presented to the driver so that he/she is constantly aware of the current status of the system (e.g., cruise control set speed, selected intervehicle separation distance, and whether or not a preceding vehicle has been detected by the system). For both systems, this information must be presented in such a fashion as to be easily understandable at a glance by the operator and in such a manner so as not to induce extra workload onto the driving task.
Based on previous research, a number of potential Driver-Vehicle Interface philosophies could be followed in the ACAS FOT program. The first, focused on in the previous CAMP program, would be to utilize a single-stage imminent collision alert which would unambiguously cue the driver that corrective action was immediately required to avoid a collision. There are a number of positive and negative aspects to this approach. On the positive side, such a single stage alert provides a clear indication to the driver that immediate corrective action must be undertaken while minimizing the amount of information presented to the driver at other points in time (i.e., the information is only presented when an imminent collision situation is detected and no additional workload is imposed on the driver at other points in time). On the negative side, no advance information regarding the potential for an imminent collision warning is provided, so the warning may potentially come as a surprise to the driver. A second approach involves the utilization of a multi-stage warning, with the initial stage providing a lower level, preparatory warning cue to the driver that an emergency response may be necessary. From a positive standpoint, such a system might serve to lessen the potential "startle" reaction on the part of the driver (a delay in response stemming from the surprise effect of a sudden collision alert). From a negative standpoint, timing for such a system is a critical issue. Set too early, such a preliminary warning may occur too often and prove annoying to the driver or be ignored routinely, drastically lessening the effectiveness of both the cautionary alert and imminent collision warning. A third approach would be to provide continuous information to the driver regarding his/her current "following" safety, taking into account such considerations as average preceding vehicle braking, road conditions, etc. and combining this with a imminent collision alert. Such an approach might have the effect of increasing inter-vehicle separation distances under manual driving conditions, thus addressing the second most common cause of rear-end collisions (inadequate following distances), as well as that of driver inattention. Previously published studies have showed promise in this regard. The one potentially negative effect of such an approach would be driver annoyance at the continuously displayed information.
The third approach detailed above has been selected as the preferred alternative for the ACAS-FOT program, though interfaces for the other two approaches will be designed and evaluated in both driving simulator and test track scenarios during the development process. The hardware selected for incorporation in the fleet vehicles is being designed to allow for maximum flexibility in terms of being able to be used for any of the three primary alternatives or variations thereof.
Milestones and Deliverables
A DVI technology exchange "Kick-Off" meeting was conducted in September of 1999 involving NHTSA, industry, and academic parties with interests/expertise in the collision avoidance arena. Relevant research in the area was identified and shared collectively among all participants. This collaboration continues as the program progresses. An interesting outcome of this information sharing was the fact that while considerable research has been performed in the area of rear-end collision avoidance displays and warnings and a lesser volume has been produced regarding adaptive cruise control interfaces, relatively little has been done addressing the human interface for a system combining both.
A DVI warning cue implementation summary report detailing the behavioral and performance issues associated with each of the possible DVI approaches will be produced and submitted to NHTSA in February 2001.
Candidate display formats have been developed for all three of the primary DVI approaches identified earlier. The primary focus has been on a gradient display as is illustrated in Figure 8.1 below. This option provides the driver with continuously updated information regarding their current "following status" relative to a preceding vehicle at all times.
Figure 8.1 Gradient Display
Earlier research has indicated that a similar display had the effect of increasing inter-vehicle spacing in the test vehicles by a significant amount, thus giving this DVI approach a potential additional positive affect not present in two alternative approaches (influencing drivers to maintain adequate vehicle separation to allow themselves time to react appropriately in potential collision situations).
An upper-level systems drawing of the DVI hardware is presented in Figure 8.2. Hardware is currently under development to produce a Head Up Display (HUD) for the FOT test fleet capable of showing any of the DVI candidate visual displays. A developmental agreement is in place with a manufacturer of visual display cells to produce a high resolution, full-color, daylight brightness unit to be employed in the HUD and prototypes are expected to be available in the first months of CY2001. The CAMP collision avoidance audio tone has been selected for use with any potential visual display and work in currently underway to develop apparatus allowing the volume of this tone to be adjusted automatically to an appropriate level based on current in-vehicle ambient sound levels. Electronics to remap the existing steering wheel controls and allow both ACC/FCW and conventional cruise functionality depending on the current phase of the FOT field-testing are also under development. A current model Buick LeSabre has been procured to serve as a development/test bench to allow prototype hardware to be designed and built to fit within the existing LeSabre instrument panel with minimal modification.
Figure 8.2 DVI Hardware
No new research has been performed to date under this task. Research will, however, be a necessary component of DVI visual format candidate refinement and eventual down selection. To this end, the Delco Electronics facility is being upgraded to include a current generation Hyperion Technologies driving simulator. This simulator allows for the real-time output of "opposing" vehicle information to be processed by the collision avoidance threat algorithms that are used to drive the driver alerts.
Plans through December 2000
During the next six months prototype hardware design, build, and test for the DVI supporting infrastructure will continue using the Delco Electronics engineering development vehicle as a test bench. The DVI candidate visual displays will undergo a refinement and test process employing Delco and GM driving simulators and the engineering test vehicles under both closed course and on-road evaluations. Variables of interest include timing parameters for all DVI candidates, utility of displayed information (whether drivers actively make use of intervehicle spacing information if provided), the distraction potential of continuously presented information, subjective (driver preference) data regarding each format, potential saliency augmentations of visual and aural cues, and the relative performance of integrated vs. discrete visual cues for following health and imminent collision (the current gradient display integrates the collision alert---tests will be performed to evaluate the efficacy of utilizing the gradient display only for following distance information and the CAMP visual alert for imminent collisions). A two-stage alternative displaying cautionary information regarding following distance and warning information regarding imminent collisions will also be evaluated.
8.3 Task B5 Schedule
[TITLE PAGE] [TABLE OF CONTENTS]
[1 Executive Summary] [2 Introduction] [3 System Integration] [4 Forward Radar Sensor]
[5 Forward Vision Sensor] [6 Brake Control System] [7 Throttle Control System]
[8 Driver-Vehicle Interface] [9 Data Fusion] [10 Tracking & Identification] [11 CW Function]
[12 ACC Function] [13 Fleet Vehicle Build] [14 Field Operational Test]
[Appendix A] [Acronyms]