Showing papers in "Transportation Human Factors in 2000"

"How Long Does It Take to Stop?" Methodological Analysis of Driver Perception-Brake Times

Abstract: Human perception-brake reaction time (RT) studies have reported a wide variety of results. By analyzing a large number of data sets, however, it is possible to estimate times under specific conditions. The most important variable is driver expectation, which affects RTs by a factor of 2. When fully aware of the time and location of the brake signal, drivers can detect a signal and move the foot from accelerator to brake pedal in about 0.70 to 0.75 sec. Response to unexpected, but common signals, such as a lead car's brake lights, is about 1.25 sec, whereas RTs for surprise events, such as an object suddenly moving into the driver's path, is roughly 1.5 sec. These times are modulated somewhat by other factors, including driver age and gender, cognitive load, and urgency.

Brake reaction times and driver behavior analysis

Abstract: In his review on driver brake reaction times (RTs), Green (2000) rightly criticizes attempts to seek a canonical brake RT, and proposes to determine expected brake RT for specific situations. However, based on his analysis, he presents a series of values for expected, unexpected, and surprise situations that appear to generalize over a variety of different driver tasks and traffic situations without sufficient concern for urgency or criticality of the situations. This sampling problem may lead easily to biased and somewhat arbitrary estimates. Thus, instead of 1.25 sec for "unexpected" situations, the median yellow response time for the critical conditions (at short time-to-stop-line) is rather below 1.0 sec, and instead of 1.5 sec mean brake RT for surprise situations, available on-road data suggest that in fairly urgent situations-at time-to-collision of about 4.0 sec-unalerted drivers are able to react to an obstacle by braking at an average latency of 1.0 to 1.3 sec, depending on site. More emphasis s...

Workload and Reliability of Predictor Displays in Aircraft Traffic Avoidance

Abstract: In 2 experiments we describe the relevance of aircraft predictor information to the availability and deployment of visual attention. In both, airplane pilots fly a simulator in which flight path prediction is given bearing on the future state of their own aircraft and of a second traffic "intruder" aircraft that they must maneuver to avoid. The cockpit traffic display on which this information is depicted is an integral component of the concept of free flight or pilot self-separation. In Experiment 1 we show that added layers of predictive information improve performance, reduce mental workload (as subjectively measured), and that added complexity of the visual display thus resulting does not increase the inferred measure of head downtime (secondary-task performance). In Experiment 2 we examine the consequences to performance and visual attention if prediction is occasionally in error. We adopt the hypothesis that trust is related to the relative allocation of attention between the predictor symbol and the raw data of actual aircraft state. Such unreliability damages performance to some extent, particularly when the unreliable predictor forecasts more complex conflict geometry. This cost reveals the substantial allocation of attention to the predictor symbol. However, pilots, knowing the level of unreliability, appear to be relatively well calibrated in their allocation of attention between the 2 information sources.

Car Drivers' Adjustments to Cyclists at Roundabouts

Abstract: The most frequent bicycle accident type at roundabouts has been shown to be between the entering driver and the circulating cyclist. On the basis of unobtrusive video recordings, in this study we show how the behavior of drivers entering the roundabout depends on the traffic situation on it. A test (stunt) cyclist was provided to create well-controlled conflict situations during the recordings. Drivers' adjustments to the test cyclist were measured in terms of approaching speed, head movements, and the manner in which they yielded to the test cyclist approaching the joint-conflict point at the bicycle crossing on a collision course, from either the left or the right. Six roundabouts in Finland, Sweden, and Denmark were included in the study, representing different roundabout layouts. The main differences were in the size of the central island and the location of the bicycle crossing. The approaching speed of the cars was lower at the roundabouts with large central islands (40-m diameter) than at those wit...

Speed reduction mechanisms of transverse lines

Abstract: The psychological mechanisms responsible for speed reductions caused by transverse lines were investigated. Using a driving simulator, 24 experienced drivers drove toward intersections with transverse lines at both reducing and constant spacing, with lines extending 0.6 m from the lane edges (peripheral transverse lines), and no lines (control), both before and after speed adaptation. All lines reduced travel speeds during the treatment areas only, and only slightly more after speed adaptation. Transverse lines reduced speeds more than peripheral lines only in the initial treatment area, and no speed differences were found between the two transverse line spacing schemes. It was concluded that transverse lines reduce speed through alerting when initially reached, and also through peripheral perception processes throughout the treatment. However, speed perception is not influenced by the decreasing spacing of the lines.

Drivers' Risk Perception of Road Design Elements

Abstract: New roads are often designed without adequate investigation of driver risk perception. However, according to many researchers, it is imperative that human factors be considered during the design of new road infrastructure. In this study we investigated driver perception of risk on 3 road sections of a single highway. For the purposes of this article, 3 field experiments took place in a 2-year period, with 136 volunteer Greek drivers taking part in these experiments. Participants evaluated the risks of road sections and curves. The results show that 3 main demographic characteristics-age, familiarity, and self-assessment-affect risk perception, whereas special provisions for older drivers during road design and construction are imperative.

Effects of overall low-beam intensity on seeing distance in the presence of glare

Abstract: Previous studies have demonstrated that current low-beam headlamps do not provide adequate seeing distance for safety. Could this situation be improved by providing more total light from low-beam headlamps, leaving the relative distribution of light unchanged? Although such a proposal is probably not the best practical solution, it is important to consider some of the visual consequences of a general increase in light to analyze the overall problem of low-beam headlighting. In a nighttime field study we measured seeing distance in the presence of glare as a function of headlamp intensity, always varying the intensity of the seeing light and glare light by the same proportion. Increasing intensity by a factor of about 3.8 increased seeing distance by about 17% for both young and old drivers. This result is consistent with predictions from quantitative vision modeling using veiling luminance to represent the disabling effects of glare. We also collected subjective estimates of discomfort glare and found, as expected, that the higher intensities produced substantially more discomfort. Our findings suggest that, if objective visual performance is the only criterion, there is no clear upper limit to how intense low-beam headlamps should be. However, there may be a level at which people simply will not tolerate the subjectively discomforting effects of glare, or at which glare indirectly affects objective performance through its effects on subjective comfort. Because subjective discomfort, rather than objective visual performance, may be the limiting consideration for setting maximum glare levels, more research should be done to understand the nature and consequences of discomfort glare, including possible effects of subjective comfort on objective visual behavior.

Top-Down and Bottom-Up Processes in Driver Behavior at Roundabouts and Crossroads

Abstract: This paper is a response by the original authors to issues raised in commentaries on their earlier article, "Car drivers' adjustments to cyclists at roundabouts," also in this journal. In the original article, the authors focused on the safety aspects of the design of roundabouts (traffic circles) and concluded the article with design recommendations. The general theoretical aspects of driver behavior and visual search, although implicit in the background throughout the article, were given a secondary role, and a comprehensive model was not the goal. The commentaries collectively suggested that the original authors outline a more explicit model of driver behavior at bicycle crossings while responding to certain controversial interpretations put forth. These points form the basis of the content of this reply piece.

Assessing road sign perception : A methodological review

Abstract: Mounting a legible and understandable road sign along the side of the road does not necessarily mean that drivers will perceive the message on that sign. Quite some research has tried to understand this principle, and by using different research methods, some insight into the process of perceiving signs has been provided. In this article I describe and discuss different research methods for studying road sign perception, all with their specific advantages and limitations. The methods described are eye movement studies, studies using verbal reports while driving, studies recording driving behavior, and studies asking drivers to recall or recognize a sign after having passed it. Although I do not claim to provide a complete overview of all available literature on road sign perception, the idea of this article is to stimulate the reader to think about drawbacks of some methodological issues when choosing methods or experimental setups dealing with investigating road sign perception. There seems to be quite a large difference between the perception of those drivers who are actively searching for some information and those drivers who are not actively searching for information. When drivers are actively searching for information, a strong contrast of the sign against the environment and the size of the sign are important factors. In the case of drivers who are not actively searching for information, the sign content in terms of the significance that the message has to the driver seems to play a crucial role. With all methods having their specific limitations, a combination of several research methods when experimentally investigating road sign perception is to be recommended. In the future, more research should be directed toward establishing the interfering effect of one method on the other, toward investigating the effects of signs on action preparedness of drivers, and toward the effect of drivers' expectations in the perception of road signs.

Driver Sleepiness-Related Problems, Health Status, and Prolonged Driving Among Professional Heavy-Vehicle Drivers

Abstract: Questionnaire data concerning the frequency of prolonged driving, sleepiness-related problems while driving and personal health status were analyzed from 567 professional drivers with 5 work descriptions. Of the drivers 31% had been regularly driving more than 10 hr, 19% reported having dozed off at least twice while driving, and 8% reported a near-miss situation due to dozing off during the past 3 months. Sleepiness-related problems while driving appeared across all driver groups, including drivers transporting dangerous goods and bus drivers, and were strongly related to prolonged driving, sleep deficit, and drivers' health status. The effects of the latter factors were interactive and cumulative: Frequent sleepiness-related problems occurred in more than one half of the drivers with the combination of prolonged driving, sleep deficit, and lowered self-perceived health. The results give unreserved support for regulating driving hours and increase concern of the connection between professional drivers he...

Incident warning systems and traffic safety: a comparison between the portico and melyssa test site systems

Abstract: In this study we compared the effects on traffic safety of 2 different incident warning systems (IWSs), capable of presenting warning messages with different levels of detail. It was assumed that an IWS presenting a message with a low level of detail (i.e., "Warning") would produce a higher variation in driver behavior compared to a system that presented more detailed information (i.e., "Warning, in 1 km, use left lane"). The assumption was tested in a simulator study in which the Portuguese Road Traffic Innovations on a Corridor and Mediterranean Lyon Stuttgart Site for Advanced Transportation Telematics test site systems were simulated and used to present information that varied in level of detail in 4 steps. Fifty participants drove an 80-km route on a 2-lane motorway, where 3 different incidents occurred at randomly chosen distances from the starting point. The results showed that all IWSs made the participants reduce their speed level earlier compared to the control group. Subjective assessment of th...

Crew Situation Awareness in High-Tech Settings: Tactics for Research Into an Ill-Defined Phenomenon

Abstract: In this article I discuss research tactics that can gain empirical access to crew situation awareness in high-tech settings, that is, in settings where multiple crew members have to coordinate their activities with those of an automated system in the pursuit of operational goals. Although deemed an important ingredient for safe and efficient operations, crew-or joint-situation awareness remains ill defined, and results regarding its demonstration or manipulation are often unverifiable and inconclusive. In this article I define the problem of crew situation awareness as it occurs in 2-crew automated cockpits and reinterprets a typical case study of crew situation awareness in light of this definition. The remainder of the article is a methodological contribution that reviews a selection of converging or complementary tactics (both field observations and various forms of simulator studies) that can gain empirical access to crew situation awareness and discusses the trade-offs these tactics represent in terms of experimental validity and reliability.

Development of a driver assist interface for snowplows using iterative design

Abstract: A system to aid snowplow operators during adverse, low-visibility conditions was developed using a quick, low-cost iterative design process. The system provided display-independent visual information on lane edges, lateral position, and potential forward collisions. Short practice curves were seen on a prototype lateral assist system with drivers achieving a steady state within 3 trials. The subsequent operational system resulted in positive driver feedback and quick learning periods. Drivers had positive impressions regarding ease of use, appeal, and safety. Behavior data showed that the short learning curves seen with the prototype could also be associated with the operational system. Using the framework of this snowplow problem, an iterative design process is also described that is robust to variations in available time and resources. Application specific and process design lessons are also discussed.

In-vehicle information systems : premises, promises, and pitfalls

Abstract: There has been considerable interest in designing and deploying in-vehicle information systems (IVIS). IVIS promises benefits to individual drivers, commercial vehicle operators, and society, such as improving safety, increasing mobility, and reducing travel time. But clumsy implementation of IVIS can impair these desirable outcomes. Our goal as transportation human factors professionals is to maximize the promise and minimize the pitfalls so that IVIS provides the driving public with a net benefit commensurate with or greater than the cost of its implementation. As a profession, we have many of the basic building blocks such as good data, control-theory models, workload estimation techniques, and human factors guidelines. In order to be successful in assembling these building blocks, we need a more theoretical understanding of how driving, IVIS, and the human driver are related.

Pilot performance during multiple failures: an empirical study of different warning systems

Abstract: Dynamic fault management-that is, dealing with a cascade of failures while maintaining process integrity-is a dominant human task in various transportation modes (e.g., commercial aviation, shipping). The way in which a warning system represents failures and the way in which the system contributes to failure management jointly determine the amount and kind of cognitive work in which the human has to engage to manage multiple failures. In this study pilot performance on 4 different commercial aviation warning systems was tested by measuring time and error rates in identifying root causes in a cascade of failures. All systems tested represent failures in the same basic way (a message list) but differ in the kind of contribution they make to the failure management task; for example, by sorting failures, prioritizing them, selecting only some failures for presentation, guiding the pilot on what to do next, or showing the pilot which systems are still operational. Human performance benefits accrued in systems that (a) provided guidance on what to do next and (b) showed which systems were still operational. These findings are consistent with the cognitive demands of dynamic fault management and carry important messages for how those demands should be supported. The results suggest that rather than automating even more of the human role in fault management to minimize error counts, attention should be paid to the kinds of referents and representations that are most useful in informing the operator of what is going on in the underlying process and how best to cope with it.

Color identification in the visual periphery: consequences for color coding of vehicle signals

Abstract: In this field study we investigated the efficiency of color coding for peripheral identification of vehicle signals. Specifically, the study dealt with identification of stimuli as yellow or red when presented at intensities corresponding to typical turn-signal lamps and side-marker lamps. Turn-signal lamps were studied both during bright, sunny conditions and at night, whereas side-marker lamps were studied at night only. We used two yellow stimuli and two red stimuli. For each color category, one stimulus was relatively far from the contrasting color category and the other stimulus was relatively near. Four viewing angles were used: 0°, 10°, 20°, and 30° from visual fixation. We tested 28 participants ranging in age from 21 to 78 years. Nighttime identification of colors was perfect at all viewing angles for stimuli representing turn-signal lamps. On the other hand, strong effects of viewing angle were found for turn-signals in the daytime and for side-marker lamps at night. Although in these 2 conditions performance deteriorated for stimuli in both color categories, it did so more for the red stimuli. This finding is consistent with the previously reported finding that peripherally presented red stimuli often appear yellow. The findings imply that coding signals yellow and red is not sufficient for their peripheral identification under the 2 most difficult conditions tested (turn signals during bright daytime and side-marker lamps during nighttime). To the extent that peripheral discriminability is important in actual driving, efficient signaling should rely on other coding parameters (e.g., intensity, and flashing vs. steady burning).

Effects of nonplanar driver-side mirrors on lane-change crashes

Abstract: In this quasi-experiment, we investigate the effects on lane-change crashes of nonplanar (spherical convex and multiradius) driver-side mirrors compared to planar mirrors. The analysis was based on 1,062 crashes reported from 1987 to 1998 to Finnish insurance companies for vehicles with passenger-side spherical convex mirrors and one of three types of driver-side mirror (planar, spherical convex, or multiradius). The results show that the mean effect of nonplanar mirrors compared to planar mirrors was a statistically significant decrease of 22.9% in lane-change crashes to the driver side. The effects of spherical convex and multiradius mirrors were not statistically different from each other. The nonplanar mirrors were beneficial especially for the high-risk driver groups, as well as for the lane-change situations and environmental conditions in which most lane-change crashes take place in the United States. These findings support the use of nonplanar driver-side mirrors. If drivers have problems with jud...

Commentary on Rasanen and Summala, "Car Drivers' Adjustments to Cyclists at Roundabouts"

Abstract: This paper presents a commentary on an earlier paper in this journal entitled, "car drivers' adjustments to cyclists at roundabouts." The focus of this commentary is on the visual search process that drivers engage in and how it is guided by top-down factors. However, these top-down factors are largely dependent on visual field objects that fit the driver's expectations. The author explores how these top-down expectancies develop and how they guide search behavior. An outline is presented containing improvements for self-explaining roads that the author posits would enhance the natural behavioral visual field search process, thereby enhancing traffic safety.

Can Applied Research Help Naval Aviation?: Lessons Learned Implementing Crew Resource Management Training in the Navy

Abstract: One challenge for applied training research is to effectively balance the need to deliver a product to meet operational requirements with the need for scientific rigor. In this article we document an applied research effort and offer lessons learned from balancing science and operational necessity while meeting naval aviation's crew resource management (CRM) training requirements. Specifically, in 1990, 60%-80% of all accidents in naval aviation were due to human error. In an effort to reduce accidents attributable to poor aircrew coordination, a program of training research was conducted. Research involving empirical and field investigations was performed and the result was strategies, methods, and tools that supported CRM training. The success of this applied training research resulted in a methodology for the design, development, and evaluation of CRM training programs for naval aviation. The methodology was used as the basis for required annual CRM training throughout naval aviation. This article disc...

The Effects of Forward Vision Restriction on Automobile Driver Posture

Abstract: A simulator study of the effects of the height of the top of the instrument panel (IP) on driving posture was conducted. Eight midsize men and 8 small women drove an interactive simulator with a large-screen display under 5 different IP-height conditions. The 3-dimensional locations of body landmarks were recorded to characterize their driving postures. In a confirmatory study, 32 men and women drove a sport-utility vehicle over a 15-min road route with and without a mask that restricted part of the windshield above the IP. These restrictions on drivers' forward vision had only small effects on driving posture. In the driving simulator, an increase in IP height of 150 mm caused drivers to sit with their hips an average of 7 mm farther forward with a hip-to-eye angle that was 1° more upright. No significant differences were found in postural response between the small female and midsize male participants. In the vehicle, no significant effects of the windshield mask on posture were observed. These findings indicate that the vision restriction imposed by the IP is unlikely to have an important effect on driving posture over the range of restriction that is reasonable for production vehicles and that predictive models of driving posture do not need to include the effects of IP height when the driver is not provided with a seat height adjustment.

The influence of impairment feedback on driver behavior: a simulator study

Abstract: A number of technological countermeasures have been proposed to reduce the incidence of accidents due to driver impairment, that is, the degradation of driving performance due to the influence of fatigue, alcohol, drugs, distraction, and emotional stress. Few studies have been concerned with those driver-system interaction issues underlying this category of technology. Eighteen male participants took part in a repeated measure design in which they performed simulated journeys with and without impairment feedback. The diagnosis and assessment of impairment were based on the quality of vehicular control. Impairment feedback was presented in the form of two interface designs, one providing 3 levels of feedback and another capable of 9 levels of feedback. The results indicate that impairment feedback counteracts the characteristic degradation of driving performance due to time-on-task with respect to vehicular control. However, the presence of feedback (in either form) failed to influence participants' decision to discontinue the journey. In addition, impairment feedback failed to significantly influence psychophysiological effort, subjective fatigue, or subjective mental workload. The implications of these findings for future research and development are discussed. Keywords: Driver distraction

Commentary on "Car Drivers' Adjustments to Cyclists at Roundabouts"

Abstract: This paper presents a commentary on an earlier paper in this journal entitled "Car drivers' adjustments to cyclists at roundabouts." The author of this commentary believes that the original paper provides important clues to vehicle--cyclist collision analysis. The author posits that it would also be beneficial to take into account the eye glance behavior of the cyclists themselves. Combining this study with an analysis of driver behavior when exiting roundabouts would provide a comprehensive and useful extension of this topic. Other suggestions are also made that the author believes would enhance the original research setting.

Commentary on "car drivers' adjustments to cyclists at roundabouts"

Abstract: This paper presents a commentary on an earlier paper in this journal entitled "Car drivers' adjustments to cyclists at roundabouts." The author discusses limitations inherent in naturalistic research efforts aimed at evaluating real-world behaviors that attempt to predict driver behavior by observing visual search patterns. Often, there are numerous confounds that prevent the discovery of a clear relation between the variables of interest. The author discusses the possibility that the failure of an automobile driver to yield to a cyclist entering a roundabout may be due to a number of factors such as the country of origin, familiarity with roundabouts as common types of intersections, and other cultural and societal factors.

Measuring the Operational Effects of Highway Geometrics: Beyond Spot Speed

Abstract: Field studies of driver behavior that are conducted to determine the operational effects of highway geometry typically involve measuring the speeds of many drivers at a few locations using roadside measuring equipment. In this article, we describe a methodology for obtaining speed estimates at many locations for a single driver using in-vehicle measuring equipment. Specifically, data from the Global Positioning System are used to define geographic coordinates of the highway and, in combination with on-board speed measurements, to provide near-continuous information of the location and speed of an instrumented test vehicle. To understand fully the impact of a particular segment of roadway geometry (e.g., a specific horizontal curve) on driver behavior, it is necessary to estimate the impact of the geometry before and after the test site. We propose an algorithm to predict whether or not a preceding curve will influence the maximum speed on the approach to a test site. This prediction is based on assumed dr...

Commentary on "Workload and Reliability of Predictor Displays in Aircraft Traffic Avoidance"

Abstract: The experiments reported by Wickens, Gempler, and Morphew (2000), address two critical issues associated with the use of cockpit displays of traffic information. These are the workload associated with the use of predictor displays and the effects of varying predictor reliability. Experiment 1 demonstrated that reliable predictive information supported conflict avoidance maneuvers while reducing mental workload. Experiment 2 examined the effect of erroneous predictive information on the allocation of attention between and dependence upon elements of the display. The results are succinctly presented and the findings provide valuable insight into the costs and benefits that may accompany the use of predictive traffic information displays in aviation. I first comment briefly on some specific aspects of the study including the (a) traffic density, (b) conflict frequency, (c) secondary task, (d) navigation demands, and (e) statistics. I conclude by addressing some general issues.

Brake reaction time and driver behavior analysis. commentary

Abstract: A commentary on an article entitled "'How Long Does It Take to Stop?' Methodological Analysis of Driver Perception-Brake Times," by Marc Green, published in this journal (Vol. 2, No. 3, 2000) is presented. The discusser agrees that the author rightly criticizes attempts to seek a cannonical brake reaction time (RT), and proposes to determine expected brake RT for specific situations. However, based on his analysis, he presents a series of values for expected, unexpected, and surprise situations that appear to generalize over a variety of different driver tasks and traffic situations without sufficient concern for urgency or criticality of the situations. This sampling problem may easily lead to biased and somewhat arbitrary estimates. Thus, instead of 1.25 seconds for "unexpected" situations, the median yellow response time for the critical conditions (at short time-to-stop-line) is rather below 1.0 seconds, and instead of 1.5 seconds mean brake RT for surprise situations, available on-road data suggest that in fairly urgent situations, at time-to-collision of about 4.0 seconds, unalerted drivers are able to react to an obstacle by braking at an average latency of 1.0 to 1.3 seconds, depending on site. More emphasis should be given to analyzing (and producing) real-life data on driver reactions as a function of situational and driver-centered variables, and of criticality. The commentary is followed by a response from the author.

Scaling up laboratory research to the "real world"

Abstract: This piece is a reply to commentary on an original article by Wickens et al. (2000) in this publication that examines the relevance of aircraft predictor information to the availability and deployment of pilots' visual attention. The author deals with comments raised regarding the limitations of the results of the laboratory experiments regarding their ability to generalize to the real world target environment of the aircraft flying in a free-flight environment.

Commentary reply [Brake Reaction Times and Driver Behavior Analysis]

Abstract: Author reply to comments by Heikki Summala concerning "Brake Reaction Times and Driver Behavior Analysis"