Many urban freeways in the United States experience congested traffic conditions during daily commute periods. Freeway system expansion is very expensive and time-consuming. Consequently, alternatives other than major construction of new facilities are desired. The Texas Department of Transportation has been implementing comparatively inexpensive methods to improve existing freeways such as grade-separated (i.e., braided) ramps and modified ramp configurations via X-ramp interchanges and ramp reversals instead of the traditional diamond interchange layout. Ramp reversal, replacement of an entrance ramp with an exit ramp or vice versa, is an improvement strategy that is increasingly recommended by outside constituencies, including developers and the public. Research was needed to develop an updated methodology and synthesize evaluation results from previously implemented ramp reversal projects to assist in future decision-making and project implementation. This research project investigated the benefits and impacts of X-ramp and ramp reversal projects. Impacts that were evaluated include operational, safety, and basic economic benefits. Case study evaluations of 15 projects implemented in Texas were performed and generally showed that ramp modification projects produce consistent benefits in all three evaluation categories. Twenty-one guidelines for successful project implementation were developed based on the project case studies and data analysis.
Abstract