Impact of Shoulder Width and Median Width on Safety

Abstract

Systematic, well-designed research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Board's recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board. The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement rather than to substitute for or duplicate other highway research programs.

Estimation of Safety Effectiveness of Composite Shoulders on Rural Two-Lane Highways

“…Results were consistent with other studies related to shoulder widening or paving projects (1,4,8). It can be concluded that the upgraded shoulders are safer both due to being wider and to being paved.…”

“…As can be seen from Figures 7,8, and 9, composite shoulders were expected to offer the most safety effectiveness, especially in respect to related crashes. Wide shoulders had similar results.…”

Minimum Inside Shoulder Width of Multi-Lane Freeway Considering the Need for Vehicle Parking

“…Median width and inside shoulder width have no statistical significance effect on safety. A similar research can be found in NCHPR Report 633 (Stamatiadis, 2009), which also examined the impact of shoulder width and median width on safety, and it was concluded that increasing shoulder width and median width both can help reduce crashes. Horst and Ridder (2007) investigated two main factors leading to singlevehicle crashes, namely, lateral position and speed.…”

Prioritizing Highway Safety Manual’s crash prediction variables using boosted regression trees

“…However, median widths of 30 ft and 100 ft would likely result in more crashes. Although median width of up to 30 ft may increase median-related crashes (Stamatiadis et al, 2009), crash likelihood due to 100 ft wide medians is counter-intuitive. Stamatiadis et al (2009) referred to the study by Hauer (2000) that concluded that "the effect of median width on total crashes is questionable".…”