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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.

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 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.

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.

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.