National Academies Press: OpenBook

Converting Paved Roads to Unpaved (2015)

Chapter: Chapter Five - Conclusions

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Suggested Citation:"Chapter Five - Conclusions ." National Academies of Sciences, Engineering, and Medicine. 2015. Converting Paved Roads to Unpaved. Washington, DC: The National Academies Press. doi: 10.17226/21935.
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Suggested Citation:"Chapter Five - Conclusions ." National Academies of Sciences, Engineering, and Medicine. 2015. Converting Paved Roads to Unpaved. Washington, DC: The National Academies Press. doi: 10.17226/21935.
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Page 25
Suggested Citation:"Chapter Five - Conclusions ." National Academies of Sciences, Engineering, and Medicine. 2015. Converting Paved Roads to Unpaved. Washington, DC: The National Academies Press. doi: 10.17226/21935.
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Page 25

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24 ments. Collecting material samples before road work reduced uncertainties and facilitated planning tasks, such as procure- ment of the correct equipment, the addition of materials as needed, and the determination of milling and mixing depths. Addressing drainage and base stabilization issues on roads being converted aided in creating a better driving surface, safer driving conditions, and in some cases, prepared the road base for future repaving. Through a survey and interviews, respondents identified the use of a reclaimer or recycler of appropriate weight and power as integral to the successful completion of the road conversion project. Respondents found these machines to be faster and more efficient than using a motor grader with a ripper or scarifier because they require less labor and provide uniform recycled material and ultimately a better driving sur- face. Reclaimed road material might be milled or crushed to 1 in. or smaller and supplemented with fines or aggregate as needed to create a smooth driving surface with reduced cob- bling. Another good practice was following the reclaimer with a padfoot roller to further break up the reclaimed material and aid in initial compaction, followed by smooth drum or rubber tire roller compaction to achieve an optimal driving surface. Numerous respondents identified the use of a chemical treatment for soil stabilization or dust control as a successful method for achieving a high-quality finished driving surface. Stabilizer use appeared to be localized to distinct climatic zones and those with similar soil types but was used in a vari- ety of situations and conditions. Dust was a common issue reported with converted roads. Stabilizers were noted to help with dust abatement, as was the application of dust suppres- sants. These procedures not only helped alleviate dust but also appeared to help road users accept the new road surface. BARRIERS TO IMPLEMENTATION Perhaps the greatest barrier to the implementation of road con- version projects is the lack of available management tools and guidance documents. Road conversions were found to be more common than originally thought. This synthesis revealed road conversions have been performed by multiple agencies in at least 26 states in the United States, as well as in Canada and Finland—far more common than initially anticipated. The limited knowledge of this practice may be the result of a lack of formal discussion on the topic, limited dissemina- IDENTIFIED EFFECTIVE PRACTICES This synthesis identified numerous practices that can facili- tate a successful road conversion project. Many survey respon- dents identified stakeholder outreach as a crucial first step before performing a conversion, specifically reaching out to residents living along the road, road users, and the gen- eral public in an act of transparency. When communicating with stakeholders, respondents also mentioned taking time to explain budgeting issues, describe the conversion process, and emphasize that the purpose of the road conversion is to improve the driving surface and safety. Letters, press releases, public meetings, and features by local news agen- cies were all cited as effective means of interacting with the public and disseminating information. Road agency person- nel, who expressed willingness to work with concerned resi- dents on issues such as dust abatement strategies, indicated that this was a successful practice. Many local road agencies use traffic counts as a common metric for setting priorities for road maintenance activities. Numerous agencies said developing and establishing an agencywide policy on which to base road surfacing, mainte- nance, and conversions would be an effective practice. This approach places the burden of maintenance decisions on data, not a single person or entity, and can reduce some aspects of the negative public perception associated with proposed con- versions. A pavement condition index, the PASER Manual, geographical information systems (GIS) databases and tech- niques outlined in handbooks such as Assessment Procedures for Paved and Gravel Roads from the Indiana Local Technical Assistance Program (LTAP) and Gravel Roads Management Tools, from the Minnesota Department of Transportation, are among the various assessment methods used to rate and track pavement condition. These tools and the associated collected data, such as traffic counts and annual maintenance costs, aid in identifying roads requiring maintenance and can be used to assess if a road needs to be rehabilitated or repaved, or con- verted from paved to unpaved. In addition, these tools aid in communicating with the public about why a road conversion may be a viable option. To ensure successful performance of a converted road, a number of agencies identified effective and cost-saving practices, including investigative work before construction, such as collecting material samples and addressing issues with drainage, base, and subgrade materials and improve- chapter five CONCLUSIONS

25 tion of available information, and a lack of communication among various local, state, and federal road agencies when a road conversion is conducted or being considered. This has prevented the sharing of information about the process of converting roads and guidance from those involved with successful and unsuccessful road conversions. A second factor that may discourage agencies from convert- ing roads is public and political perception. The general public often views paved roads as a sign of progress and perceives that converting them to an unpaved surface will decrease the quality of the road and reduce the level of service. At least ini- tially, nearly all public reaction noted by survey respondents and interviewees was negative. Residents expressed feelings of “losing ground” or “deserving better than rock” when a road was converted to an unpaved surface, and they voiced concerns about decreased safety, reduced property values, and increasing vehicle wear and tear. Dust was a primary concern identified by residents living along roads being considered for conversion. Many agencies addressed the issues of road dust by applying dust suppressants or allowing area residents to contribute funds for or perform their own dust suppression. In many cases, if a converted road was well constructed and maintained and if the local road agencies addressed concerns from the public, many residents who live along or use converted roads came to appre- ciate the safer and improved driving surface the agency was able to maintain at a higher service level than the deteriorated paved surface. Rectifying the negative perception of convert- ing paved roads to unpaved roads could be done effectively by providing case examples from agencies that have performed successful conversions. IDENTIFIED RESEARCH GAPS AND NEEDS Because of the lack of readily available and documented infor- mation on road conversions, numerous gaps in knowledge and research needs have been identified. Improved Documentation of Safety and Crash Rates on Low-Volume Roads Statistics on crash rates and crash causes for low-volume roads are not well documented. For many roads, a comparison cannot be made for crash rates before and after a road has been con- verted from paved to unpaved. There is a need for research on collection and analysis of available crash data on low-volume unpaved roads. Improved Documentation of Road Conversions Although the media frequently report on proposed road con- version projects, they rarely provide follow-up stories. There is a need for research leading to documentation of successful road conversion projects, how they were completed, and what lessons were learned. Research Leading to Guidance on a Road Conversion This study found that agencies relied on limited knowledge and experience to perform road conversion projects, with many agencies stating the project was completed “on the fly” or by “trial and error.” Many of those interviewed sug- gested that design guidance would have helped in their con- version. Specifically, they identified the following information as potentially helpful in the road conversion process: • Objective measures to identify candidate roads and determine when a conversion is to be considered; • Life-cycle cost assessment tools; • Guidance for dealing with the public and local govern- ing bodies, including example communication and pre- sentation materials; • Guidance on existing road inspection and testing, assess- ment of existing materials, thickness design, supplemen- tal material selection, construction techniques, equipment needs, projection of future maintenance needs, future potential for repaving, and options for stabilization, dust control, and surface treatments; • The development of material specifications for gravel, recycled materials, and supplemental material; • Specification language for construction and maintenance; • Case examples; • Materials and resources that can be used when com- municating with the public and local governing bodies such as cost data, pictures, and a sample presentation of successfully completed road conversions; and • Guidance on postconversion follow-up. A research needs statement has been drafted for the devel- opment of a road conversion design guide or handbook and can be found in Appendix G. Research Leading to Development of a Cost–Benefit Analysis Tool Although some agencies already use cost–benefit and life- cycle cost analysis tools to prioritize road maintenance activities (including road conversion projects), most survey respondents and interviewees did not. Many suggested a life- cycle cost analysis tool that could assist with: • Determining when a conversion will be considered a cost-effective alternative compared with continued maintenance or repaving; • Prioritizing road maintenance activities on limited budgets; • Managing data and cost for materials, maintenance, personnel, and equipment; and • Using additional analysis tools, including integration with GIS, providing further asset management, budget- ary, and public relations advantages.

26 Road Conversions in Areas Affected by Heavyweight Vehicles This topic is covered in a related report, NCHRP Synthesis 469: Impacts of Energy Developments on U.S. Roads and Bridges. This report mentions the need for future research, includ- ing the collection of safety and crash statistics on impacted rural roads, improved methods for both pavement and geo- metric design of impacted rural roads, and engineering-based methods for detour routing during periods of high-activity energy development. Research on Environmental Impacts Associated with Road Conversions The largest potential environmental impact related to road conversions discussed by survey respondents was the issue of dust and its effect on health and safety. No documented studies have been conducted that compare dust levels before and after conversion. Survey respondents also reported that potential impacts associated with erosion of the reclaimed road surface and the use of surface stabilizers and dust abate- ment products need to be quantified.

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TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 485: Converting Paved Roads to Unpaved explores how common and under what conditions paved roads are converted to unpaved.

NCHRP Synthesis 485 found that the practice of converting paved roads to unpaved is relatively widespread; recent road conversion projects were identified in 27 states. These are primarily rural, low-volume roads that were paved when asphalt and construction prices were low. Those asphalt roads have now aged well beyond their design service life, are rapidly deteriorating, and are both difficult and expensive to maintain. Instead, many local road agencies are converting these deteriorated paved roads to unpaved as a more sustainable solution.

According to the report, local road agencies have experienced positive outcomes by converting roads. Many local road agencies reported cost savings after converting, compared with the costs of continuing maintenance of the deteriorating paved road, or repaving. One key to successful conversion is early involvement of the public in the planning process. Other techniques that can be used to improve the overall results of a project include treating or stabilizing granular surfaces to control dust, limiting the rate of aggregate loss, and reducing motor grader/blade maintenance frequency. Stabilization procedures can also improve safety, increase public acceptance, and reduce life-cycle costs and environmental impacts after a conversion has taken place.

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