The Cost-Effectiveness of Clear-Zone Width through Rock-Cuts in Rural Two-Lanes Undivided Roadways

Clear-zones are a feature of modern highways and have a dramatic impact on roadside safety. The purpose of these unobstructed spaces is to provide an area where an errant vehicle can stop safely or where a driver can regain control of the vehicle without striking a hazardous object like a tree or a utility pole. This article examines different clear-zone improvement alternatives in rock-cuts and compares the likely effect on safety and construction costs. Where a roadway passes throught rockcuts, the construction costs of providing the clearzone is very high. This article is based on a research that demonstrates a method for selecting the appropriate clear-zone in rural two-lane highways in Iran based on the site and traffic conditions expected at the site. A method is described for determining the rock-cut width that best balances the cost of construction with the improvements in safety that would result from a wider clear-zone in the rock-cut.