Accommodating Oversize/Overweight Vehicles at Roundabouts.

摘要

Safety and traffic operational benefits of roundabouts for the typical vehicle fleet (automobiles and small trucks) have been well documented. Although roundabouts have been in widespread use in other countries for many years, their general use in the United States began only in the recent past. 1990 is generally accepted as the year the first modern roundabouts were built in the United States (US), but their use is growing. Roundabouts can offer several advantages over signalized and stop-controlled intersection alternatives, including better overall safety performance, lower delays, shorter queues, better management of speed, and opportunities for community enhancement features. However, potential use of roundabouts with all their benefits may be greatly diminished if they cannot accommodate oversize/overweight vehicles (OSOW). Accommodating OSOW at roundabouts is the central issue and the need for this research. Note that the acronym OSOW has been used in this report as a universal term, generally understood to mean a permitted vehicle. OSOWs impact pavement structure, roadway geometrics, and traffic operations. These issues are discussed in the report. OSOWs are a reality for American industry and often critical for certain industries. A better understanding and sharing of current practices is essential for states that permit such movement, and the industry which must rely on state highways and a permit to deliver large loads. Thus, the main objectives of this report are to compile current practice and research by various states and countries related to the effects OSOW have on roundabout location, design, and accommodation. Second, the research will attempt to fill in information gaps with respect to roundabout design and operations for this class of vehicles. A literature review uncovered no published reports on OSOW accommodation per se; however, much information on the advantages of having designated truck and OSOW networks is analyzed and reported. The authors make an argument that states should consider conducting a study to develop a freight network, which includes segments where OSOW need to be accommodated, in accordance with state and federal commerce laws and policies and the states economy. The study should include determining all motor vehicles whose size and turning movements are critical to developing routes on which all segments will accommodate these vehicle. To obtain information on the state-of-the art of OSOW accommodation, the authors turned to personal contacts, unpublished material, case studies and surveys.