Safety and Operational Evaluation of Shoulders on Urban Freeways

摘要

The study addresses two issues concerning shoulder removals: safety and traffic operations. Improvement of traffic flow is the primary reason for considering shoulder removals. However, extensive removal of both shoulders appears to be counter productive. Overall safety is improved on study sections where inside shoulders are removed to add capacity on very congested roadways (ADT greater than 20,000 vehicles per lane per day) and the congestion is reduced (ADT per lane less than 18,000 vehicles per lane per day). The improved safety appears to be the result of improved traffic operation. If congestion is less severe, then safety appears to be unchanged where inside shoulders are removed. Inside shoulder removals appear to be preferable to outside shoulder removals.