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

The relationship between municipal highway expenditures and sociodemographic status: Are safety investments equitably distributed?

Different population groups have varying transportation needs based on their region type, socio‐economic, and socio‐demographic characteristics. Yet, municipal highway funding allocation methods do not typically consider these differences. Throughout the United States, municipal highway funding allocation is based upon fixed formulas that often only account for highway mileage and/or population size rather than equal benefits and funding outcomes across different population groups. This potentially creates an inequitable funding allocation process leading to safety and accessibility disparities between different population groups. This research investigates the extent to which the distribution of resources is not equal when evaluated by population group. Specifically, the relationship between municipal highway expenditures and poverty levels, population aged 65 years and older, race, and remoteness is investigated using data from the states of New York and Massachusetts. Using linear regression techniques, several models were developed that relate municipal highway expenditures with the socio‐economic and socio‐demographic characteristics of municipalities. The results revealed that there are clear municipal highway expenditure disparities between different population groups. Municipalities that have higher poverty levels experience a lower highway expenditure rate per local mile. Further, municipalities located in remote areas far from large metropolitan regions experience a disproportionately lower highway expenditure rate per local mile. Moreover, the results of this study indicate the need to consider how funding methods can address social differences

Backing collisions: a study of drivers\u27 eye and backing behaviour using combined rear-view camera and sensor systems

Context—Backing crash injures can be severe; approximately 200 of the 2,500 reported injuries of this type per year to children under the age of 15 years result in death. Technology for assisting drivers when backing has limited success in preventing backing crashes. Objectives—Two questions are addressed: Why is the reduction in backing crashes moderate when rear-view cameras are deployed? Could rear-view cameras augment sensor systems? Design—46 drivers (36 experimental, 10 control) completed 16 parking trials over 2 days (eight trials per day). Experimental participants were provided with a sensor camera system, controls were not. Three crash scenarios were introduced. Setting—Parking facility at UMass Amherst, USA. Subjects—46 drivers (33 men, 13 women) average age 29 years, who were Massachusetts residents licensed within the USA for an average of 9.3 years. Interventions—Vehicles equipped with a rear-view camera and sensor system-based parking aid. Main Outcome Measures—Subject’s eye fixations while driving and researcher’s observation of collision with objects during backing. Results—Only 20% of drivers looked at the rear-view camera before backing, and 88% of those did not crash. Of those who did not look at the rear-view camera before backing, 46% looked after the sensor warned the driver. Conclusions—This study indicates that drivers not only attend to an audible warning, but will look at a rear-view camera if available. Evidence suggests that when used appropriately, rear-view cameras can mitigate the occurrence of backing crashes, particularly when paired with an appropriate sensor system

Fuzzy Sets to Describe Driver Behavior in the Dilemma Zone of High-Speed Signalized Intersections

The Type II dilemma zone describes a segment of road on the approach to a signalized intersection where, if occupied by a motorist presented with the circular yellow indication, is likely to result in a motorist having difficulty deciding to stop at the stop line or proceed through the intersection. This phenomenon results in increased frequency of three failure conditions: rear-end collision at the stop line (excessive deceleration rates), the more severe right-angle crashes in the intersections, and left-turn head-on collisions (both resulting from incorrect estimates of clearance time). A more effective boundary definition for Type II dilemma zones could contribute to the safe design of signalized intersections. The prevailing approaches to dilemma zone delineation include the consideration of the vehicle’s travel time to the stop line or the driver’s likelihood of stopping at a particular distance from the stop line. The imprecision of the driver’s perception of speed and distance suggest that fuzzy logic may contribute to the identification of the Type II dilemma zone boundaries. A fuzzy logic (FL) model was constructed and validated from driver’s empirically observed behavior at high-speed signalized intersections. The research resulted in an increased understanding of the phenomenon which, when applied to the timing of signals and the placement of vehicle detection, can improve the overall safety of signalized intersections.This is the authors' peer-reviewed accepted manuscript, which is copyrighted by Elsevier. The final version of record can be found here: http://www.journals.elsevier.com/transportation-research-part-f-traffic-psychology-and-behaviour/Keywords: Dilemma zone, Safety, Driver behavior, Signalized intersection

Activation of Akt by the Bacterial Inositol Phosphatase, SopB, is Wortmannin Insensitive

Salmonella enterica uses effector proteins translocated by a Type III Secretion System to invade epithelial cells. One of the invasion-associated effectors, SopB, is an inositol phosphatase that mediates sustained activation of the pro-survival kinase Akt in infected cells. Canonical activation of Akt involves membrane translocation and phosphorylation and is dependent on phosphatidyl inositide 3 kinase (PI3K). Here we have investigated these two distinct processes in Salmonella infected HeLa cells. Firstly, we found that SopB-dependent membrane translocation and phosphorylation of Akt are insensitive to the PI3K inhibitor wortmannin. Similarly, depletion of the PI3K regulatory subunits p85α and p85ß by RNAi had no inhibitory effect on SopB-dependent Akt phosphorylation. Nevertheless, SopB-dependent phosphorylation does depend on the Akt kinases, PDK1 and rictor-mTOR. Membrane translocation assays revealed a dependence on SopB for Akt recruitment to Salmonella ruffles and suggest that this is mediated by phosphoinositide (3,4) P2 rather than phosphoinositide (3,4,5) P3. Altogether these data demonstrate that Salmonella activates Akt via a wortmannin insensitive mechanism that is likely a class I PI3K-independent process that incorporates some essential elements of the canonical pathway

Automated Analysis of Cryptococcal Macrophage Parasitism Using GFP-Tagged Cryptococci

The human fungal pathogens Cryptococcus neoformans and C. gattii cause life-threatening infections of the central nervous system. One of the major characteristics of cryptococcal disease is the ability of the pathogen to parasitise upon phagocytic immune effector cells, a phenomenon that correlates strongly with virulence in rodent models of infection. Despite the importance of phagocyte/Cryptococcus interactions to disease progression, current methods for assaying virulence in the acrophage system are both time consuming and low throughput. Here, we introduce the first stable and fully characterised GFP–expressing derivatives of two widely used cryptococcal strains: C. neoformans serotype A type strain H99 and C. gattii serotype B type strain R265. Both strains show unaltered responses to environmental and host stress conditions and no deficiency in virulence in the macrophage model system. In addition, we report the development of a method to effectively and rapidly investigate macrophage parasitism by flow cytometry, a technique that preserves the accuracy of current approaches but offers a four-fold improvement in speed

Structural and Biochemical Characterization of SrcA, a Multi-Cargo Type III Secretion Chaperone in Salmonella Required for Pathogenic Association with a Host

Many Gram-negative bacteria colonize and exploit host niches using a protein apparatus called a type III secretion system (T3SS) that translocates bacterial effector proteins into host cells where their functions are essential for pathogenesis. A suite of T3SS-associated chaperone proteins bind cargo in the bacterial cytosol, establishing protein interaction networks needed for effector translocation into host cells. In Salmonella enterica serovar Typhimurium, a T3SS encoded in a large genomic island (SPI-2) is required for intracellular infection, but the chaperone complement required for effector translocation by this system is not known. Using a reverse genetics approach, we identified a multi-cargo secretion chaperone that is functionally integrated with the SPI-2-encoded T3SS and required for systemic infection in mice. Crystallographic analysis of SrcA at a resolution of 2.5 Å revealed a dimer similar to the CesT chaperone from enteropathogenic E. coli but lacking a 17-amino acid extension at the carboxyl terminus. Further biochemical and quantitative proteomics data revealed three protein interactions with SrcA, including two effector cargos (SseL and PipB2) and the type III-associated ATPase, SsaN, that increases the efficiency of effector translocation. Using competitive infections in mice we show that SrcA increases bacterial fitness during host infection, highlighting the in vivo importance of effector chaperones for the SPI-2 T3SS

Niche-specific profiling reveals transcriptional adaptations required for the cytosolic lifestyle of <i>Salmonella enterica</i>

AbstractSalmonella enterica serovar Typhimurium (S. Typhimurium) is a zoonotic pathogen that causes diarrheal disease in humans and animals. During salmonellosis, S. Typhimurium colonizes epithelial cells lining the gastrointestinal tract. S. Typhimurium has an unusual lifestyle in epithelial cells that begins within an endocytic-derived Salmonella-containing vacuole (SCV), followed by escape into the cytosol, epithelial cell lysis and bacterial release. The cytosol is a more permissive environment than the SCV and supports rapid bacterial growth. The physicochemical conditions encountered by S. Typhimurium within the cytosol, and the bacterial genes required for cytosolic colonization, remain unknown. Here we have exploited the parallel colonization strategies of S. Typhimurium in epithelial cells to decipher the two niche-specific bacterial virulence programs. By combining a population-based RNA-seq approach with single-cell microscopic analysis, we identified bacterial genes/sRNAs with cytosol-specific or vacuole-specific expression signatures. Using these genes/sRNAs as environmental biosensors, we defined that Salmonella is exposed to iron and manganese deprivation and oxidative stress in the cytosol and zinc and magnesium deprivation in the SCV. Furthermore, iron availability was critical for optimal S. Typhimurium replication in the cytosol, as well as entC, fepB, soxS and sitA-mntH. Virulence genes that are typically associated with extracellular bacteria, namely Salmonella pathogenicity island 1 (SPI1) and SPI4, had a cytosolic-specific expression profile. Our study reveals that the cytosolic and vacuolar S. Typhimurium virulence gene programs are unique to, and tailored for, residence within distinct intracellular compartments. Therefore, this archetypical vacuole-adapted pathogen requires extensive transcriptional reprogramming to successfully colonize the mammalian cytosol.Author SummaryIntracellular pathogens reside either within a membrane-bound vacuole or are free-living in the cytosol and their virulence programs are tailored towards survival within a particular intracellular compartment. Some bacterial pathogens (such as Salmonella enterica) can successfully colonize both intracellular niches, but how they do so is unclear. Here we have exploited the parallel intracellular lifestyles of S. enterica in epithelial cells to identify the niche-specific bacterial expression profiles and environmental cues encountered by S. enterica. We have also discovered bacterial genes that are required for colonization of the cytosol, but not the vacuole. Our results advance our understanding of pathogen-adaptation to alternative replication niches and highlight an emerging concept in the field of bacteria-host cell interactions.</jats:sec

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