Raymond J. Kiefer

Toward Developing an Approach for Alerting Drivers to the Direction of a Crash Threat

Objective: This study explored the potential for auditory and haptic spatial cuing approaches to alert drivers to the direction of a crash threat. Background: For an automobile equipped with multiple crash avoidance systems, effective cuing of the crash threat direction may help the driver avoid the crash. Because the driver may not be looking in the direction of a visual crash alert, nonvisual crash alerts were explored as an additional means of directing attention to a potential crash situation. Methods: In this in-traffic study, 32 drivers were asked to verbally report alert direction in the absence of any crash threats. Driver localization accuracy and response time were examined as a function of eight alert locations surrounding the vehicle and four directional alert approaches (auditory, haptic, haptic and auditory, and haptic and nondirectional auditory). The auditory directional alert approach used four speakers and broadband alert sounds, and the haptic directional alert approach used vibrations generated at various locations on the bottom of the drivers seat. Results: Overall, relative to the auditory alert approach, the three approaches that included the haptic seat alert component reduced correct localization response times by 257 ms and increased percentage correct localization from 32% to 84%. Conclusion: These results suggest that seat vibration alerts are a promising candidate for alerting drivers to the direction of a crash threat. Application: These findings should facilitate developing a multimodality integrated crash alert approach for vehicles equipped with multiple crash avoidance systems.

Time-to-Collision Judgments Under Realistic Driving Conditions

Objective: This study examined perceived time to collision (TTC) with automobile drivers under realistic approach, rear-end crash scenario conditions. Background: TTC refers to the time before impact if prevailing conditions continue. Method: In this test track study involving 51 drivers ranging from 20 to 70 years old, the drivers vision was occluded at either 3.6 or 5.6 s TTC during an in-lane approach to a lead vehicle. Drivers provided TTC estimates by pressing a button the instant they felt that they would have collided with the vehicle ahead. Results: Results indicated that TTC was consistently underestimated. The TTC ratio (perceived TTC/actual TTC) increased as driver speed decreased and as relative speed increased. These ratios were largely unaffected by age, gender, actual TTC, viewing time (1 s vs. continuous), and the presence of an eyes-forward, mental addition distraction task. Conclusion: Overall, these results suggest that under these low TTC conditions drivers estimate TTC in a relatively uniform fashion and that they are capable of providing this estimate based on a brief glimpse to the vehicle ahead. Application: These results are being used to develop an alert timing approach for a forward collision warning system intended to assist drivers in avoiding rear-end crashes with the vehicle ahead.

A Tactile Seat for Direction Coding in Car Driving: Field Evaluation

This in-traffic, field study examined the merit of using a car seat instrumented with tactile stimulation elements (tactors) to communicate directional information to a driver. A car seat fitted with an 8 times 8 matrix of tactors embedded in the seat pan was used to code eight different directions (the four cardinal and four oblique directions). With this seat mounted in a car, a field study was conducted under both smooth road and brick road vibratory conditions. The primary performance measures were directional accuracy and reaction time, measured under both alerted and simulated surprise conditions. Overall, the results show that the tactile chair seat provides a promising and robust method of providing directional information. The percentage of correct directional responses was very high (92 percent of all trials), and incorrect responses were typically just one location segment (45 degrees) off.

Direction coding using a tactile chair

This laboratory study examined the possibility of using a car seat instrumented with a tactile display to communicate directional information to a driver. A car seat fitted with an 8 x 8 matrix of vibrators embedded in the seat pan was used to code eight different directions. Localization response time and angular accuracy were examined as a function of stimulus direction, presence of a tactile attention cue, temporal pattern, stimulus layout, age, and gender. The mean absolute angular error was 23 degrees, and both localization accuracy and response times were superior for the back left, backward, and back right directions. Of the various temporal pattern/attention cue combinations examined, results favored the relatively fast patterns consisting of vibration bursts of 125 or 250 ms without a centrally located attention cue over 500 ms bursts that were preceded by an attention cue. Observed age and gender effects were relatively modest, suggesting that using tactile cueing to communicate direction is effective across a wide range of users. In addition, the tactile stimulus was detected by more than 90% of the participants under surprise trial conditions. Overall, these results indicate that the tactile chair provides a promising and robust method of providing directional information.

Design and Evaluation of a Prototype Rear Obstacle Detection and Driver Warning System

This study, concerned with the development of driver interface criteria for a rear obstacle detection system, assessed the appropriateness of alternative warning timing algorithms and evaluated various interface approaches for presenting warning information to drivers. Interface testing used a minivan and a passenger sedan equipped with a prototype rear obstacle detection system. Two different warning timing algorithms and four different interface conditions were examined. The appropriateness of the warning timing algorithms was tested using an alerted backing procedure wherein drivers backed to known obstacles and braked in response to the warning. A surprise event scenario was also included in order to examine driver reaction to the warning under unexpected conditions. Alerted backing results suggest that although both timing algorithms led to few target strikes, one algorithm led to more acceptable ratings, fewer target strikes and close calls, and less urgent braking. None of the interface warning conditions reliably induced avoidance braking under the surprise event condition. Actual or potential applications of this work include the appropriate design of effective backing warning systems.

Comprehension testing of active safety symbols

This paper describes an effort to develop a valid and reliable process for comprehension testing of candidate automotive symbols and to conduct comprehension testing on a set of new symbols being considered for invehicle active safety systems. The comprehension testing process was developed though a multi-year effort, supported by Society of Automotive Engineering (SAE) and other organizations, aimed at generating a test methodology that would: yield high-quality comprehension data for new automotive symbols, provide clear and specific guidance back to symbol developers based on the test results, and could be adopted and performed internationally to support international standards efforts. Seventeen (17) candidate symbols were evaluated for three classes of in-vehicle active safety systems: forward collision warning (4 symbols), side collision warning (6 symbols), and lane departure warning (7 symbols). So far, testing has been completed in Germany, Sweden, Japan, and the United States. In the US testing, the study yielded comprehension data, appropriateness rankings, and diagnostic design feedback for all 17 icons tested. Based on these data, US recommendations have been made to the International Standards Organization (ISO) for all three classes of in-vehicle safety systems. This paper describes the process associated with developing the procedure, including the international outreach required to obtain support from major ISO countries, as well as the methods and results from the US testing.

Identifying the Pattern of Localization Responses with a Haptic Seat Intended to Alert Drivers to the Direction of a Crash Threat

The potential safety benefits afforded by emerging automotive crash avoidance systems may be enhanced by implementing a driver vehicle interface (DVI) that effectively communicates the direction of a potential crash threat in a timely, effective, and integrated manner. An in-traffic study by the authors provided evidence that drivers could spatially map eight haptic seat vibration areas to the corresponding directions surrounding the vehicle with 86% localization accuracy (Fitch, Kiefer, Hankey, & Kleiner, 2007). This paper re-analyzed the data from this study to explore the extent to which there were any notable patterns in the observed localization errors. Results indicate there was some tendency for subjects to perceive side (i.e., left or right) seat pan vibration locations as originating somewhat further back than they actually occurred. Furthermore, the pattern of these errors suggest that a haptic seat communicating four directions of crash threat (e.g., front, right, back, and left) may further reduce the low level of localization errors observed with an eight direction haptic seat design.

Reduction of Backing Crashes by Production Rear Vision Camera Systems

Today’s automotive Rear Vision Camera (RVC) systems display an image to the driver of an area behind the vehicle generated by a camera located in the rear of the vehicle. This paper examined if, and to what extent, these systems offered on a wide variety of production vehicles are addressing backing crashes (estimated to represent approximately 3%-4% of all annual police-reported crashes in the United States). Police-reported crashes from ten United States state crash databases were examined to determine the frequency of backing crashes and control (baseline) crashes. The logistic regression model developed suggests that production RVC systems examined may be reducing overall police-reported backing crashes by 52%. This is a particularly promising finding because these systems may also be helping to avoid additional backing crashes that have not been reported to the police. This research can be used to inform emerging crash avoidance system-related system consumer metrics (e.g., New Car Assessment Program (NCAP) programs), government regulations surrounding RVC systems, and system performance requirements associated with RVC consumer metrics and regulations.