Safety and Cost-Effectiveness of Clearzones in Rockcuts

Clearzones are a feature of modern highways that have a dramatic impact on roadside safety. The purpose of these unobstructed spaces is to provide an area where an errant vehicle can safely stop or the driver can regain control of the vehicle without striking a hazardous object like a tree or utility pole. Many clearzone alternatives (e.g., removing trees, installing traversable culvert openings, and installing guardrails in front of untraversable hazards) are relatively inexpensive in comparison to other roadway construction costs. Roadways passing through rockcuts present an unusual case where the construction cost of providing the clearzone is very high. This article examines different clearzone alternatives in rockcuts and compares the likely effect on safety and construction costs. A method is described for determining the rockcut width that best balances the cost of construction with the improvements in safety that would result from a wider clearzone in the rockcut.