Adequacy of minimum passing sight distances for completing or aborting the passing maneuver
Ohene, Frederick A.
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Overtaking and passing maneuvers on two-lane rural roads is still one of the most complex situations drivers are faced with in everyday driving. In passing, drivers must judge the speed, acceleration and deceleration capabilities of their own vehicle, that of the impeding vehicle and the speed and rate of closure of the oncoming vehicle. They also have to make decisions on the adequacy of an acceptable gap and sight distance. This report presents an investigation of the adequacy of the current "Manual on Uniform Traffic Control Devices" (MUTCD) for marking on two-lane, two-way roads. It examines the existing criteria, problems associated with it and its reasonableness. Passing sight distances which incorporates both the option of aborting or completing the passing maneuver is presented. A model describing the kinematics of vehicle trajectories during the passing maneuver on two-lane roads is utilized for this purpose. The model is based on the presence of a delima zone during the passing maneuver. At this point, the decision to complete or abort the passing maneuver provides the same factor of safety. This critical position is located using the model. The parameters that strongly influence the required sight distance are investigated. Thus passing sight distances that will provide reasonable margin of safety throughout the passing maneuver will be achieved. It is realized from the results that the current MUTCD passing sight distance is inadequate from a safety standpoint, except for high accelerations and high decelerations.
- Masters Theses