Geometric Design Practices for Resurfacing, Restoration, and Rehabilitation (2011)

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31 CHAPTER FIVE SUMMARY OF FINDINGS AND RECOMMENDATIONS FOR FURTHER RESEARCH 6. Although there are wide variations in the scope of the 3R guidelines, nearly all states include design levels or at least discussions for the 13 controlling design ele- ments. Design speed, lane width, and shoulder width are the geometric design criteria that are viewed as the most critical for 3R projects. 7. Several states indicated that other design criteria should be included. The most cited features were clear zone; intersection sight distance; and accommoda- tions for pedestrians, bicyclists, and Americans with Disabilities Act requirements. 8. Nearly all states responded that there are unanswered issues regarding the 3R program. The key issues appear to be the following: • What is the appropriate degree of improvement to enhance safety? • Prioritizing upgrades to address geometric deficiencies when all cannot be met. • Lack of a national standard to determine the minimum design criteria that can be applied to a 3R project. • Better guidance on what type of improvements should be made for pedestrians and bicyclists and when are projects exempt from improving bicycle and pedestrian accommodations. Some key questions still remain. Is it better to improve more projects to less stringent but adequate standards than to build fewer projects to currently accepted standards for new highway construction? Is it better to construct only those safety features that are cost-effective rather than bringing every feature of every project up to the latest standards? The conundrum facing highway officials is how to decide which well-serving objectives can be met most cost-effectively. The recommended research stemming from this synthe- sis can be summarized as two major needs: 1. A general research need is to continually advance the state of the art of the relationship of the various design elements, individually or in combination, to safety. States need to know what safety benefit will be derived from an improvement in any geometric Under the current federal law, states may set their own design criteria and standards for resurfacing, restoration, and rehabil- itation (3R) projects, with FHWA approval. Given that allow- ance, wide variations are to be expected in the states’ 3R policy and geometric design guidelines. According to the state survey responses, their practices can be summarized as follows: 1. All but eight states have an FHWA-approved 3R policy. The remaining eight states have similar pro- grams and design policies that have been developed to achieve the same purpose—extend the service life and enhance the safety of the selected road. 2. The number of 3R projects implemented annually varies widely among the states, from as few as 2 to 3 to as many as 500 to 600 projects. This variation is not directly related to the size of the state or the mile- age under its control, but rather depends on the types of improvements made under 3R. The large numbers of 3R projects reflect projects that involve only pave- ment improvements, whereas those with only a few projects involve more improvements. 3. The time necessary for implementing 3R projects also vary widely among the states, ranging from a few months to 2 or more years. This variation also relates to the type of 3R project and the need for spe- cial studies, including environmental reviews and citizen vetting. 4. Nearly all states routinely consider safety improve- ments in developing 3R projects. The three safety improvements most frequently implemented as part of a 3R project are (1) barrier upgrades, (2) shoul- der addition or widening, and (3) clear zone obstacle removal or shielding. 5. Although many states include safety improvements, there appears to be limited use of analytical assess- ments of safety beyond “looking at crash data.” The use of new safety analysis tools and methods, such as road safety audits/assessments, the application of the information in the new Highway Safety Manual, the Interactive Highway Safety Design Model, and Safe- tyAnalyst, is only just emerging.

32 2. States need a proven optimization model or program that would allow them to decide how best to allocate their limited funds for 3R improvements. Within a given budget cycle, there will be competing projects, each of which is likely have a net benefit. Selecting projects from a simple ranking of highest to lowest benefit or benefit to cost will not always yield the most effective allocation of funds. Several factors affect project selection, and to the extent possible these fac- tors should be captured within an optimization pro- gram for rational selection of projects. element alone and in combination with others. With “perfect” information on these relationships, states will be able to select safety improvements that will yield the largest safety return for the available funds for any specific 3R project or for their entire annual 3R program. This effort would include developing crash prediction models for various design elements under different conditions of road types, volume lev- els, and other influencing variables, and expanding the database on crash reduction/modification factors for individual safety improvements.