Improving the Traffic Operations and Safety of Ramps and Speed Change Lanes - A Review of State Design Practices

摘要

The report presents the results of a review of ten selected state highway design manuals, discussions with state design and traffic operation engineers and a literature review with specific attention given to ramp and speed change lane criteria. For comparison, additional documents from the American Association of State Highway and Transportation Officials (AASHTO) and Canada were reviewed. A summary of the review and analysis of the manuals is provided along with a detailed discussion of selected design parameters of ramps and speed change lanes. The review determined that the manner in which individual design elements are fitted together can be improved by providing that a complete section of roadway (e.g. a ramp) be designed to insure a proper smooth speed transition (SST) exists. This can be done by studying a proposed design from the beginning to end and recording the speed transition expected.