I am trying to calibrate AASHTO Passing Sight Distance (PSD) for our developing countries highway. I am worried about the data needed and process of calibration.
The first question is it related to junction control? Unsignalized junctions or roundabouts, where generally gap acceptance theory is greatly applied? Then you need the critical gap and follow-up headway values.
About calibration of the passing sight distance (kinematic) model as often used in AASHTO since 40's you need to know; the passing duration, speeds of passing and passed vehicles, the speed difference, acceleration characteristics, and time to collision.
However, the kinematic model assumes infinite length of passing zone as there is no reference to the marked passing zone. My recent work has been to correct this discrepancy between the design and marked PSD.
Hello Sohel,
For gap acceptance, you can check the sight triangles at intersections (approach and departure) were the decision sight distance is controlling (DSD). DSD has different formulas based on intersection control and movement rank.
For PSD, you may need to look (test) at perception reaction time, passing time, speeds of passing and passed vehicles, acceleration.
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