Evaluation of Dynamic Passing Sight Distance Problem Using a Finite-Element Model

Sufficient passing sight distance is an important control for two-lane rural highway design to minimize the possibility of a head-on collision between passing and opposing vehicles. Traditionally, passing zones are marked by checking passing sight distance that is potentially restricted by static sight obstructions. Such obstructions include crest curves, overpasses, and lateral objects along highways. This paper proposes a new concept of dynamic sight-distance assessment, which involves restricted passing sight distances due to the impeding vehicles that are traveling in the same direction. Using a finite-element model, the dynamic passing sight-distance problem was evaluated, and the writers analyzed the relationships between the available passing sight distance and other factors such as the horizontal curve radius, impeding vehicle dimensions, and a driver’s following distance. It was found that the impeding vehicles may cause substantially insufficient passing sight distances, which may lead to potential traffic safety problems. It is worthwhile to expand on this safety issue and consider the dynamic passing sight distance in highway design.