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This research, funded by the United States Department of Transportation Federal Highway Administration, is one of the early initiatives to investigate the potential of advanced technologies to impr...

Cooperative-adaptive cruise-control (CACC) offers the potential to increase roadway capacity by decreasing the size of gaps between vehicles. However, smaller gaps may reduce drivers’ ability to sa...

Objective This field study examined the effects of adaptive cruise control (ACC) on mind wandering prevalence. Background ACC relieves the driver of the need to regulate vehicle speed and following distance, which may result in safety benefits. However, if ACC reduces the amount of attentional resources drivers must devote to driving, then drivers who use ACC may experience increased periods of mind wandering, which could reduce safety. Methods Participants drove a prescribed route on a public road twice, once using ACC and once driving manually. Mind wandering rates were assessed throughout the drive using auditory probes, which occurred at random intervals and required the participant to indicate whether or not they were mind wandering. Measures of physiological arousal and driving performance were also recorded. Results No evidence of increased mind wandering was found when drivers used ACC. In fact, female drivers reported reduced rates of mind wandering when driving with ACC relative to manual driving. Driving with ACC also tended to be associated with increased physiological arousal and improved driving behavior. Conclusion Use of ACC did not encourage increased mind wandering or negatively affect driving performance. In fact, the results indicate that ACC may have positive effects on driver safety among drivers who have limited experience with the technology. Application Driver characteristics, such as level of experience with in-vehicle technology and gender, should be considered when investigating driver engagement during ACC use. Field research on vehicle automation may provide valuable insights over and above studies conducted in driving simulators.

This chapter provides an overview and recap of the AVS 2019 Breakout Session AVs & Vulnerable Road Users: Representing the Under-Represented, including summaries of research and perspective presentations from leading experts in the field and needs identified through discussion among panelists and the session audience. The session identified a range of necessary actions and research needs including defining technological, improving education about automation and advanced technology, and using these to build public trust.

Roadwork that results in a lane closure can reduce both the safety and efficiency of a roadway. The dynamic merge is a form of merge control designed to mitigate the potential hazards of lane closures by customizing the merge environment to suit the current level of traffic. When traffic is light, early merge signs encourages drivers to merge into the open lane prior to queue formation. When traffic is heavy, late merge signs encourages drivers to remain in the closed lane for as long as possible. The current study used a driving simulator to assess the independent effects of traffic volume and dynamic merge messaging on merge location and traffic throughput. Merge location was influenced by merge environment, such that drivers in the early merge condition merged earlier than those in the late merge condition regardless of traffic volume. In addition, when traffic was heavy, participants in the late merge condition passed through the work zone more quickly than those in the early merge condition. The results are suggestive of the beneficial effects of the late merge on traffic throughput and the effectiveness of the dynamic merge messaging in influencing merging behavior.

This study explored human factors issues associated with cooperative adaptive cruise control (CACC); specifically entering and exiting vehicle platoons. Participants were asked to complete one of three different types of merges in a driving simulator: (1) manual left entrance merge, (2) merge into the middle of a CACC platoon vehicles without speed assistance, and (3) merge into the middle of a CACC platoon vehicles with speed assistance. Drivers’ perceived workload was significantly less for both groups that drove with the CACC system engaged than for the group that manually maintained speed. Perhaps surprisingly, participant condition did not significantly affect physiological arousal as assessed by galvanic skin response (GSR). However, across all groups, GSR was significantly greater during the merges than during cruising/straight highway driving time periods. The two groups that had to manually adjust speed during the merge experienced collisions in 24 (18 percent) of the merges. A possible explanation, supported by participant feedback, is that drivers expect others to act in a courteous manner and to create larger gaps for entrance on to a freeway – something that may not be possible in real world CACC deployment.

Roadway lane reduction transitions have long been reported to be problematic to drivers. It is not known whether this is the result of a lack of understanding of lane reduction markings, a simple failure to comply with such markings, or other unknown factors. This study explored driver comprehension of six different lane reduction markings. The markings varied in terms of the incorporation and length of dotted and broken lines. In addition, half of the markings included a solid white line adjacent to the dotted/broken line. The supplemental solid white line resulted in improved understanding that the rightmost lane would end, earlier reported lane changes, and the highest preference ratings. Dotted lines also resulted in better understanding of an upcoming necessary lane change than did the longer, more traditional broken lane lines. Recommendations and suggestions for lane reduction marking changes to the Manual of Uniform Traffic Control Devices are made.

This study explored human factors issues associated with cooperative adaptive cruise control (CACC); specifically the relationship between drivers’ preferred following distance, assigned following distance, and driving performance. Participants drove in a dedicated lane and experienced a vehicle merging in front of their vehicle and later, an emergency event that required intervention in order to avoid a collision. Drivers followed at either a near or a far distance. Drivers’ perceived workload did not vary between the cruise and postmerge periods. However, workload was significantly greater after the emergency crash event. Workload did not vary significantly based on following distance assignment or preference. Those participants assigned to the near following distance were more likely to hover their foot over the brake during the merging event and to react faster to the emergency event. As with workload, performance (collision avoidance) did not vary significantly due to following distance assignment or preference. In other words, one’s abilities may not necessarily reflect their following preferences. This is a promising finding for widespread implementation of CACC.

There is little known about the effect of both reduced weight bearing and exposure to radiation during spaceflight on the mechanically-sensitive cartilage lining the knee joint. In this study, we characterized cartilage damage in rat knees after periods of reduced weight bearing with/without exposure to solar-flare-relevant radiation, then cartilage recovery after return to weight bearing. Male Sprague Dawley rats (n = 120) were either hindlimb unloaded (HLU) via tail suspension or remained weight bearing in cages (GROUND). On day 5, half of the HLU and GROUND rats were 1 Gy total-body X-ray irradiated during HLU, and half were sham irradiated (SHAM), yielding 4 groups: GROUND-SHAM; GROUND-IR; HLU-SHAM; and HLU-IR. Hindlimbs were collected from half of each group of rats on day 13. The remaining rats were then removed from HLU or remained weight bearing, and hindlimbs from these rats were collected on day 62. On day 13, glycosaminoglycan (GAG) content in cartilage lining the tibial plateau and femoral condyles of HLU rats was lower than that of the GROUND animals. Likewise, on day 13, immunoreactivity of the collagen type II-degrading matrix metalloproteinase-13 (MMP-13) and of a resultant metalloproteinase-generated neoepitope VDIPEN was increased in all groups versus GROUND-SHAM. Clustering of chondrocytes indicating cartilage damage was present in all HLU and IR groups versus GROUND-SHAM on day 13. On day 62, after 49 days of reloading, the loss of GAG content was attenuated in the HLU-SHAM and HLU-IR groups, and the increased VDIPEN staining in all treatment groups was attenuated. However, the increased chondrocyte clustering remained in all treatment groups on day 62. MMP-13 activity also remained elevated in the GROUND-IR and HLU-IR groups. Increased T2 relaxation times, measured on day 62 using 7T MRI, were greater in GROUND-IR and HLU-IR knees, indicating persistent cartilage damage in the irradiated groups. Both HLU and total-body irradiation resulted in acute degenerative and pre-arthritic changes in the knee articular cartilage of rats. A return to normal weight bearing resulted in some recovery from cartilage degradation. However, radiation delivered as both a single challenge and when combined with HLU resulted in chronic cartilage damage. These findings suggest that radiation exposure during spaceflight leads to and/or impairs recovery of cartilage upon return to reloading, generating long-term joint problems for astronauts.

For driving research and training. it is desirable to replicate a single driving scenario across multiple driving simulator platforms. However, until recently, the task of developing and implementing the same scenarios across multiple platforms has not been undertaken. The present paper assesses such an effort across of three different simulator platforms. To evaluate the effort from a visual perspective, a combination of subjective and objective measures were used. The manipulation of environmental visual complexity was also assessed. While the manipulation of visual complexity was only partially successful, each of the three simulator sites was able to create extraordinarily similar driving scenarios. These results open the door for a wide range of driving simulator studies and applications.

Introduction Research has shown that both pedestrians and drivers drastically overestimate pedestrians' nighttime visibility (NHSTSA, 2008a, 2008b; Owens & Sivak, 1996) and fail to appreciate the safety benefits of proven conspicuity aids. One solution is educational intervention (Tyrrell, Patton, & Brooks, 2004); however, the on-road assessment of its effectiveness is expensive and time consuming. Method Experiment One introduces a computer-based alternative to the field-based approach, successfully replicating the previous study's trends among 94 students who either receive or do not receive an educational lecture. Experiment Two utilizes the simulation's portability to determine if professional roadway workers have a more accurate understanding of pedestrian conspicuity than students. Results: Results among 88 workers show they do not significantly appreciate the advantages of effective retroflective material configurations or vehicle headlamp settings, for example, any better than non-lectured students in Experiment One. Impact: The study's results demonstrate the need for education among all pedestrians and the benefits of efficient testing methods.

Although it is clear that pedestrians typically overestimate how conspicuous they are to oncoming drivers at night, little is known about the factors that affect pedestrians' estimates of their own conspicuity. This study explored the extent to which pedestrians judge that their own conspicuity is affected by headlight intensity and their clothing. Forty eight participants walked to and from a parked vehicle until they felt they were conspicuous to the driver. Unknown to the participants, headlight intensity was manipulated between subjects by filtering the vehicle's high beams. Estimated recognition distances did not change with variations in headlight intensity even when up to 97% of the illumination from the headlights was blocked. This suggests that when pedestrians judge their own conspicuity they do not consider the magnitude of the headlight illumination that reaches them. Participants estimated that their recognition distances were only somewhat shorter when wearing black clothing relative to more reflective clothing. Together these findings underscore the need to educate pedestrians about their own nighttime conspicuity. Language: en

Headlights must balance two conflicting goals: maximizing visibility for the driver and minimizing glare to other drivers. Yet, recent increases in the number of complaints about headlights indicate a consumer focus on glare discomfort and not on poor visibility - a known causal factor of nighttime crashes. This study, as part of a series of experiments, explored the relationship between subjective and objective consequences of glare. Twenty-four participants used a psychophysically based technique to estimate their visual acuity in the presence of three different glare intensities. Actual acuity and subjective reports of discomfort were also assessed. Observers' estimates of acuity significantly worsened as glare intensity increased, yet actual acuity was unaffected. Overall, estimates of the disabling effects of glare were more tightly correlated with subjective reports of glare-induced discomfort than with actual visual performance. These results, which are consistent with data obtained in the field - using vehicle headlights as the glare source - may help explain drivers' reluctance to use their high beams. The results also underscore the need to collect data on disability glare, not just discomfort glare, when evaluating new lighting technologies. Language: en

Headlights must balance the conflicting goals of maximizing visibility for the driver and minimizing glare to others. Yet consumer complaints about headlights tend to emphasize only glare. This project extended earlier research by asking 17 young drivers to judge the distance at which they would be able to recognize the orientation of a non-retroreflective stimulus adjacent to the headlights of a stationary opposing vehicle. The beam setting (low vs. high) of both vehicles was manipulated. Participants correctly estimated that the stimulus would be less visible when their own vehicle used low beams and when the opposing vehicle used high beams. Contrary to earlier studies that used high contrast (retroreflective) stimuli, drivers' estimates of conspicuity were, on average, not significantly different from the actual visibility of the stimulus. These results suggest that drivers' understanding of headlight glare is more accurate for low contrast stimuli than for high contrast (retroreflective) stimuli and that drivers may overestimate the disabling effects of opposing headlights for higher contrast objects more than for lower contrast objects. Language: en

In 2000, the Institute of Medicine published To Err Is Human: Building a Safer Health System which stated that between 44,000 to 98,000 patient deaths occur annually due to largely preventable medical errors. While this number is staggering, the number of errors adversely affecting patients in ways other than death must be much greater. The goal of the current study was to determine the types of in-hospital drug-related medical errors that occur, as well as to quantify the proportion and severity of those errors. A lack of consistency across studies in hospital error reporting prevented an accurate analysis of drug-related errors and their severity. The authors recommend future studies (and hospitals alike) adhere to, at minimum, five guidelines in error reporting. It is hoped that with standardized reporting methods a better understanding of medication-related errors can be gained, thus resulting in the design and implementation of error-reducing measures.

Exploring how biological motion can make pedestrians more conspicuous to drivers at night, one-hundred-and-twenty participants were driven along an open-road route at night and pressed a button whenever they recognized that a pedestrian was present. A test pedestrian wearing black clothing alone or with 302 cm2 of retroreflective markings in one of four configurations either stood still or walked in place on an unilluminated sidewalk. Participants' response distances were maximal for the full biological-motion configuration and remained surprisingly long when convenient subsets of reflective markers were positioned on the pedestrian's ankles and wrists. When the pedestrian wore a reflective vest, the responses were no better than when he wore no reflective markings. The biological-motion advantage actually results from interacting form-perception and motion-perception mechanisms. These results confirm that basic perceptual phenomena—observers' sensitivity to human form and motion—can be harnessed to reduce an important problem of traffic safety.

While considerable data indicate that positioning retroreflective markings on a pedestrian's extremities can dramatically enhance nighttime conspicuity, most relevant safety devices (vests) limit coverage to the torso. We asked 120 participants to press a button whenever they recognized that a pedestrian was present during a short drive at night. A test pedestrian wearing different configurations of retroreflective markings was positioned on the left shoulder of an unilluminated two-lane roadway. Compared to an ANSI class-II vest alone, response distances were significantly greater when the vest was supplemented with ankle markings and when a full biological motion configuration was worn. Conspicuity was also greater when the pedestrian was walking and when facing the approaching test vehicle. Relative to a full eleven-element biological motion configuration, adding just two retroreflective ankle straps to a conventional safety vest is considerably more practical while still providing substantial conspicuity benefits.

In response to a federal mandate, all new light passenger vehicles in the United States will soon be required to include tire pressure monitoring systems (TPMSs) that alert drivers when one or more tires become 25% or more underinflated relative to the pressure level recommended by the vehicle manufacturer. Although the goal of TPMSs is to reduce the population of underinflated tires, their ultimate effect on tire pressure in consumer vehicles is unknown. Tire pressure and survey data were collected from approximately 1,200 vehicles that had just entered a rest area from an Interstate highway. Comparisons between vehicles with and without a TPMS were made from 864 vehicles in the full sample and from a subset of 123 target vehicles. The presence of TPMSs was generally associated with a small (0.7 to 1.5 psi) but significant decrease in the severity of tire underinflation. In addition, vehicles equipped with TPMSs were significantly less likely to have at least one tire that was 25% or more underinflated. The effect of TPMSs on tire pressure might have been larger had the systems been designed to activate at a less severe underinflation level. Less than 2% of survey respondents believed that TPMSs should have a trigger threshold as extreme as the currently mandated 25% threshold. Surveys also revealed that drivers without a TPMS do not report large differences in their tire maintenance behaviors relative to drivers with a TPMS and that more than 25% of drivers of vehicles with a TPMS are unaware that their vehicle is so equipped.

The present study used simulator sickness questionnaire data from nine different studies to validate and explore the work of the most widely used simulator sickness index. The ability to predict participant dropouts as a result of simulator sickness symptoms was also evaluated. Overall, participants experiencing nausea and nausea-related symptoms were the most likely to fail to complete simulations. Further, simulation specific factors that increase the discrepancy between visual and vestibular perceptions are also related to higher participant study dropout rates. As a result, it is suggested that simulations minimize turns, curves, stops, et cetera, if possible, in order to minimize participant simulation sickness symptoms. The present study highlights several factors to attend to in order to minimize elevated participant simulation sickness.

Various systems exist to classify roadway environments; however most do not consider driver-relevant perceptual components. A perceptually based roadway classification system has the potential to support the placement of signage (or removal of extraneous clutter) in the right-of-way as a means to enhance driver performance. The present study sought to determine which environmental factors are attended to by roadway users. Thirteen participants first rated the similarity of 14 roadway environments and then rated each environment on 5 different descriptors (built-up, clutter, openness, aesthetically pleasing, organized/predictable). The resultant data were analyzed using a methodology rarely taken advantage of in the field of transportation: Multidimensional Scaling (MDS). MDS revealed the participants relied on two primary dimensions when rating the similarity of the roadway environments. These two dimensions related closely with: 1) organization/predictability and 2) clutter and aesthetics. This methodology provides a simple way to gain access to drivers’ perceptions of the roadway environment and appears to be a promising first step toward developing a user-focused roadway classification system.

Headlights must balance two conflicting goals: maximizing visibility for the driver and minimizing glare to other drivers. Yet consumer complaints about headlights tend to focus on glare and not on poor visibility – a known casual factor of nighttime roadway crashes. These reactions may help to explain why drivers tend to underuse high beam headlights. This study explored the relationships among objective (impaired visual performance) and subjective (reports of discomfort and participants’ judgments of glare-induced visual impairments) consequences of headlight glare. Sixteen participants sat in a vehicle that moved slowly on a closed road and estimated the distance at which they could determine the orientation of a retroreflective Landolt C. Actual recognition distances and reports of glare-induced discomfort were also assessed. Observers’ overestimated the extent to which glare degraded their ability to see the target. Participants’ estimates of their own acuity decreased significantly when the opposing vehicle used high beams despite the fact that their actual acuity was unaffected. Overall, estimates of the disabling effects of glare were more tightly correlated with subjective reports of glare-induced discomfort than with actual visual performance. These results, which are consistent with psychophysical data obtained in a laboratory setting, may help explain drivers’ reluctance to use their high beams. The results also underscore the need to collect data on disability glare, not only discomfort glare, when evaluating new lighting technologies.

Ten small patches of retroreflective material were evaluated using a method of magnitude estimation to quantify the effect of changing the coefficient of retroreflection (RA) on brightness perception. Seventeen undergraduates participated. The results show that brightness is tightly linked with RA. Brightness was influenced more by changes in lower RA than changes in higher RA and follows Steven’s power law for brightness. Practical and theoretical implications are discussed.

One of the tools that the United States Federal Highway Administration uses to evaluate highway infrastructure-signs, roadway markings, and geometric features-is a driving simulator. The nature of the research necessitates that important visual information is perceived similarly in the simulated world as in the real-world. Perceptual mismatches can lead to incorrect assumptions about driver behaviors and understanding of new or novel roadway designs. Because of limitations in simulator projector technology, and the lack of true depth in images projected onto a cylindrical scene, it is often necessary to adjust the size of projected objects. The objects may need to be scaled up or down relative to 1:1 equivalence of image projected on the retina in order to produce a detectable object or a desired apparent distance. For example, to achieve an appropriate legibility distance for highway signs, signs are scaled up to achieve a mean legibility distances of 1 inch of letter height per 60 feet of (simulated) viewing distance. On the other hand, to attain a 1:1 correspondence with real-world following distances between the subject vehicle and the vehicle ahead, simulated vehicles are scaled down to 75 percent of the correct retinal image size. The methods and theories for arriving at these scale factors are described. The need to scale up highway signs is believed to be related to resolution and contrast limitations of current technology projectors. The need to scale down vehicle sizes may be the result of a Ponzo illusion, in which the converging lines of highway lane markings distort the apparent size of vehicles ahead. Before using a driving stimulator to conduct studies of driver perception or behavior in response to out of vehicle stimuli, it is important to examine assumptions concerning the size of projected images and their detectability and perceived distance. Meeting abstract presented at VSS 2015. Language: en

Every year there are nearly 43,000 traffic fatalities and it is estimated that 25% of crashes involve some degree of driver inattention (NHSTA, 2005, 2000). A recent survey revealed 21% of crashes/near crashes reported by respondents involved at least one driver using a mobile phone (Seo & Torabi, 2004). The current study examined the effects of mobile phone use on drivers' attention and eye movements in a low-fidelity simulator. Sixteen Clemson University undergraduate students viewed 24 driving scenarios and responded to questions about vehicular events in the scenes. Eight participants simultaneously performed a language learning task (simulating a mobile phone conversation). The language learning group answered fewer questions about the driving scenes correctly (M = 9.3) than the non-language group (M = 16). Overall, participants' correctly responded to more scenarios with 4 cars (M = 7.3/12) than with 7 cars (M = 5.3/12). The total number of fixations on the vehicle(s) involved in the critical event in each scenario was greater for the non-language group (M = 471.7) than for the language group (M = 300.5). Additionally, participants in the language group who answered the event question correctly spent the same percentage of the total time looking at the vehicle of interest during the event (M = 13.5%) as those people who answered incorrectly (M = 12.4%). This finding provides support for the 'look but fail to see' phenomenon. The mean duration of total fixations was also greater for people in the non-language group (M = 9574.5 ms) than the language group (M = 6523.4 ms). This study supports previous findings that increasing mental workload (through mobile phone use, and/or increased traffic) decreases driving performance.