Car following and dynamic dilemma zone model for determining gate operation times based on driver behavior at highway-rail intersections

The primary safety benefit from four quadrant gates is that they assure no intersection violations after the gate arms are lowered, unless the gate arms are penetrated. The implementation of four quadrant gates, while eliminating gate arm violations by motorists, does present the potential for trapping a vehicle. A critical issue is determining gate operation time parameters to minimize the likelihood of trapping a vehicle between the entry and exit gates. Driver behavior relative to stopping or proceeding at various speeds is the primary determinant of the likelihood of clearing the intersection. If implementation of four quadrant gates is to be undertaken, there needs to be design criteria which assure the safety of motorists based on human factors related to the operation of four quadrant gates and the likelihood of clearing the crossing or stopping in an appropriate manner.; This study introduces the concept of a "dynamic dilemma zone" road segment. A dynamic dilemma zone as opposed to a static dilemma zone is a road segment on approach to an intersection which varies in length based on fluctuations in vehicle speeds and the number of vehicles within a road segment. This is in contrast to a static dilemma zone which is based on a constant on changing approach speed and single vehicle in the road segment. The "dilemma" refers to the interaction of vehicle kinematics and perception-reaction time, where a vehicle could not clear the 'intersection' or stop before entering it. Car-Following theory is used within the dynamic dilemma zone approach to model driver-vehicle behavior in platoons. The determination of the dynamic dilemma zone aids in defining the conditions which contribute to the likelihood of vehicle clearance (or stopping) at four quadrant gate highway-rail intersections.; Field data is collected and analyzed from two highway-rail intersections. Vehicular speed profiles are examined in the approach zone, stopping distance zone, and the track zone for single vehicles as well as platoons of vehicles. A simulation model incorporating the field data, determination of a dynamic dilemma zone, and algorithms to determine gate operation times is developed and validated. The results from this approach yield four quadrant gate operation parameters applicable to higher traffic volume conditions where four quadrant gate design criteria have not been considered.