Tracking Driver Eye Movements at Permissive Left-Turns

The objective of this analysis was to identify sources of informationused by left-turning drivers. To complete the experiment, a virtual network ofsignalized intersections was created for use in a driving simulator equipped withhead and eye tracking equipment. Fourteen drivers were recruited to participate inthe experiment, which included two independent variables (permissive signalindication and presence of opposing traffic). The primary dependent variable wasthe associated eye movements at permissive left-turns, including the magnitude oftime focused on each potential cue and the pattern in which cues were detected.To complete the analysis, eye movements were tracked and the screen wasdivided into “areas of interest,” which coincided with potential cues used in thecompletion of a permissive left turn. For each permissive scenario, drivers usedmore total cues when no opposing traffic was present. Specifically, in theabsence of opposing traffic, drivers fixated on a wider array of availableinformation. When opposing traffic was present, drivers spent a majority of timefocused on opposing traffic and would use this as a base point from which theywould glance at other data sources. Overall, drivers looked at least once at theprotected/permissive left-turn (PPLT) signal display and the opposing trafficstream. Drivers tended to scan the intersection from right to left, after initiallylocating the PPLT signal display and opposing traffic and/or stop bar area. Theresults of the eye movement analysis are consistent with data obtained in afollow-up static evaluation

Static and Dynamic Evaluation of the Driver Speed Perception and Selection Process

Speed impacts the extent to which mobility and safety are experienced across the surface transportation network. By expanding current understanding of speed perception and selection processes our ability to understand and comprehensively address speed-related issues will improve. Driving simulator technology has advanced the field of transportation research. However, it has been limited in its application to speed-related issues. Furthermore, static computer-based evaluations have been used as a means of establishing a preliminary understanding for driver interpretation of stimuli encountered in the roadway, but have been limited in their application to speed. These technologies allow for large sample populations to be evaluated quickly and safely. Phase I of this initiative examined driver ability to perceive travel speeds in a similar real world, simulated world, and static environment. The experimental course traversed roadway where land-use and posted speed limits varied. Drivers’ actual and perceived speeds were recorded at 20 identical “checkpoint” locations in each environment, and the results were analyzed across drivers and environments. Phase II examined three roadway attributes that impact the speed-selection process. A focus group was employed to build improved scenarios of interest for a full-scale static evaluation. In the static environment, 75 drivers were asked how fast they would travel while individual characteristics of the scenario displayed were modified. This multifaceted research initiative expands the potential application of advanced technology in speed-related research, and improves the understanding of factors that influence speed perception and selection processes

Assessment of the Introductory Transportation Engineering Course and the General Transportation Engineering Curriculum

Transportation engineering is a critical subdiscipline of the civil engineering profession as indicated by its inclusion on the Fundamentals of Engineering Examination, its overlap with other specialty areas of civil engineering, and as recognized by the Transportation Research Board, Institute of Transportation Engineers, and the American Society of Civil Engineers. With increasing transportation workforce needs, low numbers of students entering the ‘pipeline’, and limited hours within undergraduate civil engineering programs, it is important to ensure civil engineering students receive adequate preparation and exposure to career opportunities in the transportation engineering field. As such, investigations into the status of transportation engineering within civil engineering programs and specifically the introductory transportation engineering course are essential for understanding the implications to the profession. This paper presents a review of relevant literature and findings from a new survey of ABET-accredited civil engineering programs that yielded 84 responses. The survey indicates that 88 percent of responding programs teach an introductory course in transportation engineering, and 79 percent require it in their undergraduate programs. There is significant variation in the structure of the introductory course (number of credit hours, lab requirements, etc.), and common responses regarding improvements that could be made include adding labs, requiring a second course, and broadening course content. In addition, nearly 15 percent of instructors teaching the introductory course did not have a primary focus in transportation engineering. This finding should be investigated further, given that this course may be an undergraduate civil engineering student’s only exposure to the profession.This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Transportation Research Board of the National Academies and can be found at: https://doi.org/10.3141/2328-0

Multicopy Single-Stranded DNA Directs Intestinal Colonization of Enteric Pathogens

Multicopy single-stranded DNAs (msDNAs) are hybrid RNA-DNA molecules encoded on retroelements called retrons and produced by the action of retron reverse transcriptases. Retrons are widespread in bacteria but the natural function of msDNA has remained elusive despite 30 years of study. The major roadblock to elucidation of the function of these unique molecules has been the lack of any identifiable phenotypes for mutants unable to make msDNA. We report that msDNA of the zoonotic pathogen Salmonella Typhimurium is necessary for colonization of the intestine. Similarly, we observed a defect in intestinal persistence in an enteropathogenic E. coli mutant lacking its retron reverse transcriptase. Under anaerobic conditions in the absence of msDNA, proteins of central anaerobic metabolism needed for Salmonella colonization of the intestine are dysregulated. We show that the msDNA-deficient mutant can utilize nitrate, but not other alternate electron acceptors in anaerobic conditions. Consistent with the availability of nitrate in the inflamed gut, a neutrophilic inflammatory response partially rescued the ability of a mutant lacking msDNA to colonize the intestine. These findings together indicate that the mechanistic basis of msDNA function during Salmonella colonization of the intestine is proper production of proteins needed for anaerobic metabolism. We further conclude that a natural function of msDNA is to regulate protein abundance, the first attributable function for any msDNA. Our data provide novel insight into the function of this mysterious molecule that likely represents a new class of regulatory molecules