01024471

Component

Passing sight distance (PSD) is provided to ensure the safety of passing maneuvers on two lane two way roads. Many variables decide the minimum required length for a safe passing maneuver. These variables include, but not restricted to, the passing vehicles’ speeds, the passed vehicles’ speeds, vehicle lengths, deceleration rate, etc. They are random variables and represent a wide range of human and vehicle characteristics. Current PSD design practices replace these random variables by single-value means in the calculation process, disregarding their inherent variations, which results in a single-value PSD design criteria. The authors believe that these variables need to be replaced by adequate probability distributions that capture most of the variations in the parameters. The main objective of the paper is to derive a PSD distribution that accounts for the variations in the contributing parameters. Two models are devised for this purpose, a Monte-Carlo simulation model and a closed form analytical estimation model. The Monte-Carlo simulation model uses random sampling to select the values of the contributing parameters from their corresponding distributions in each run. A different PSD value is calculated in each trial representing a different set of conditions. The analytical model accounts for each parameter variation by using their means and standard deviations in a closed form estimation method. The means and standard deviations of the PSD using both models are compared for verification purposes. Both models use the same PSD formulation. Three road-design speeds (40, 50 and 60 mph) are considered in the analysis. A PSD distribution is developed for each speed design. The results of both models differ only by less than 5 percent. The obtained distributions are used to estimate the reliability index of the current PSD standards, classified by the design speed of the road.

01020180

06-0225

English

22p

2006

Transportation Research Board 85th Annual Meeting

CD-ROM

Figures; References; Tables

Field tests; Human factors; Monte Carlo method; Passing lanes; Passing sight distance; Passing zones; Random sampling; Simulation; Traffic speed; Vehicle characteristics

Analytical methods; Closed form analytical estimation model; Passing distance; Passing lane spacing

Highways; Safety and Human Factors; I95: Vehicle Inspection

Transportation Research Board Annual Meeting 2006 Paper #06-0225

TRIS, TRB

Mar 3 2006 10:18AM