Browsing by Subject "Left turns"

Now showing 1 - 4 of 4
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    Bus Driver Intersection Task Analysis: Investigation of Bus-Pedestrian Crashes
    (Intelligent Transportation Systems Institute, Center for Transportation Studies, University of Minnesota, 2013-01) Wei, Chia; Becic, Ensar; Edwards, Christopher; Manser, Michael
    The current report includes two specific research efforts. The primary objective of the first research effort was to conduct a task analysis of a left-turn maneuver by a bus driver. The goal of this task analysis was to provide insight into the cognitive and perceptual processes that bus drivers complete while performing a left-turn maneuver. An additional goal of the first research effort included the development of potential countermeasures that could help reduce the frequency of bus-pedestrian collisions. The interviews conducted as part of the task analysis revealed that drivers engage in a large number of subtasks and cognitive/perceptual processes when completing a left-turn maneuver. We proposed two potential interventions for the reduction of bus/pedestrian collisions. One of the proposed interventions was designed to aid a driver in detection of pedestrians at a crosswalk. The second intervention was designed to remove a need to perform a particular attention-demanding subtask to reduce the cognitive and perceptual load that drivers experience during this maneuver. The second research effort was designed as a pilot simulator study in which we examined the potential effectiveness of proposed interventions. The second study uncovered unanticipated findings (i.e., high rate of collisions with pedestrians) that may be due to the nature of the simulator studies – lack of real-world consequences. The results of the pilot study provided sufficient data for further examination of different support tools for the reduction of the fatalities between left-turning buses, and also uncovered potential relationship between work-related stress and the impact on driving performance.
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    Development of Guidelines for Permitted Left-Turn Phasing Using Flashing Yellow Arrows.
    (Minnesota Department of Transportation, 2015-06) Davis, Gary A.; Hourdos, John; Moshtagh, Vahid
    The objective of this project was to develop guidelines for time-of-day use of permitted left-turn phasing, which can then be implemented using flashing yellow arrows (FYA). This required determining how the risk for left-turn crashes varied as traffic-flow conditions varied during the course of a representative day. This was accomplished by developing statistical models, which expressed the risk of occurrence of a left-turn crash during a given hour as a function of the left-turn demand, the opposing traffic volume, and a classification of the approach with respect to the opposing traffic speed limit, the type of left-turn protection, and whether or not opposing left-turn traffic could obstruct sight distance. The models were embedded in a spreadsheet tool which will allow operations personnel to enter, for a candidate intersection approach, existing turning movement counts, and a classification of the approach with respect to speed limit, turn protection, and sight distance issues and receive a prediction of how the risk of left-turn crash occurrence varies throughout the day, relative to a user-specified reference condition.
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    Field Study of Driver Behavior at Permitted Left-Turn Indications
    (Intelligent Transportation Systems Institute, Center for Transportation Studies, University of Minnesota, 2013-03) Davis, Gary A.; Mudgal, Abhisek
    A digital video camera was used to record left-turning vehicles and through vehicles at an urban intersection. A total of 39 left-turn events, with a total of 195 gap decisions, were identified and vehicle trajectories corresponding to those were extracted from the video and transformed into real coordinates using photogrammetry. Bayes estimates of each opposing vehicle’s distance, speed, and time-to-arrival were then computed from the trajectories and used as predictors in logit models of acceptance/rejection decisions. It was found, when models are penalized for the numbers of their parameters, that arrival time, the ratio of initial distance to initial speed, was best predictor. This contrasts with an earlier study that found distance clearly superior to arrival time. This may be due to the fact that in the current study, speeds and initial distances were substantially higher than in the earlier study.
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    The Left Turn
    (1993-10) Hancock, Peter A.; Caird, J.K.
    Two experiments are reported which examined drivers' responses in turning left across a line of traffic as presented in a closed-loop, interactive, fixed-base driving simulator. Drivers were located near an intersection and instructed to turn left across a stream of on-coming traffic when they felt that it was safe for them to do so. The on-coming stream of traffic was varied in terms of the physical parameters of approach velocity, inter-vehicle time interval, and vehicle type. Specifically, seven velocities (10-70 mph) were crossed with seven gap sizes (3-9 sec) to yield forty-nine within-subject conditions for each of four, between-subject, vehicle types; motorcycle, compact car, large car, and delivery truck. There were ten subjects per vehicle type, giving a total of forty participants in the first experiment. Results indicated differential acceptance of gap and velocity combinations depending upon the type of approaching vehicle. Collisions tended to occur along the boundaries where driver's decisions to reject or accept turns were ambivalent. They also occurred with greater frequency at higher velocity approach rates. The second experiment replicated the procedure of the first experiment except that the subjects were older drivers, uniformly over the age of 55. Results indicated a greater degree of turn conservatism for this later group. Overall, turn decisions were not dependent upon a single physical parameter such as vehicle velocity or inter-vehicle distance, although gap-size generated an arguable influence. Rather, left turn decisions appeared to result from the complex interplay of rate-of-change perceptual variables such as "time-to-arrival" and the perceived characteristics of the vehicles themselves. Implications of the results are discussed with respect to the perception of vehicles and turn safety at roadway intersections.