NCHRP Report 420, "Impacts of Access Management Techniques," classifies access management techniques and presents methods for predicting the safety and operational effects of the different techniques. For some techniques, quantitative assessment is not practical, and so case studies are presented to demonstrate good and poor practice. This report will be very useful to those developing access guidelines and policy and to those analyzing specific access situations.

Access management provides two major benefits to the transportation system: (1) the preservation of highway capacity and (2) improved safety. The FHWA report, Access Management for Streets and Highways, was published in 1982, and, although much of its contents are still applicable, many subsequent studies and reports have identified new access management techniques and offered guidance on their application. Transportation agencies and real estate developers sought better methods for analyzing, selecting, and predicting the impacts of access management techniques.

Under NCHRP Project 3-52, Urbitran Associates and its subcontractors listed and classified more than 100 access management techniques. A comprehensive literature search was performed for each of these techniques, and the results were synthesized. The techniques are evaluated on the basis of how widely they can be applied to the road network and the likelihood that their benefits can be expressed quantitatively. Twelve techniques were selected for further study and were consolidated into eight categories (i.e., traffic signal spacing, unsignalized access spacing, corner clearance criteria, median alternatives, left-turn lanes, U-turns as alternatives to direct left turns, access separation at interchanges, and frontage roads).