National Academies Press: OpenBook

Converting Paved Roads to Unpaved (2015)

Chapter: Chapter Three - Summary of Survey Results

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Suggested Citation:"Chapter Three - Summary of Survey Results ." 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 Three - Summary of Survey Results ." 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 Three - Summary of Survey Results ." 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 Three - Summary of Survey Results ." 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 Three - Summary of Survey Results ." 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 19

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16 taining the road was the most significant reason for converting it (Figure 11). Safety concerns were also indicated as a rea- son in nearly half the conversions, whereas public complaints were cited in about one-third of instances. A combination of the three reasons was cited as the impetus for conversion by 16 of these 57 respondents. For many local road agencies that participated in the survey, the final decision to convert a road from paved to unpaved was made by the county commissioner or county or supervisory board, or based on recommenda- tions from the county engineer or highway superintendent or manager. For many responding agencies, most road conversions were conducted in the past 5 years (2010 to 2015). Of the 52 responses received regarding road performance after the conversion, 44 indicated that the road was performing well, 43 noted that the conversion has saved the local road agency money, and 35 responded that there has been no documented increase in vehicle crashes on the converted roads or road segments. Despite these results, sentiment from those affected by the road conversions has been split, with 19 respondents noting a positive reaction from road users and 26 reporting a negative reaction. Pressure to repave the converted roads was identified by 29 of the 53 respondents answering this question. Despite this public negativity, 20 of the responding local road agencies plan to convert more roads from paved to unpaved in the future. Responses from the survey indicate that the use of outreach efforts by local road agencies to communicate the occurrence and process of road conversions to the public was evenly split, with half indicating that some form of outreach was performed and half noting their absence. Outreach efforts commonly included public meetings; meeting with stakeholders and resi- dents who lived along the road being converted; and to a lesser extent, letters sent to affected homeowners or use of local media (television news reports, radio, newspaper arti- cles, and press releases). Most local road agencies that used outreach efforts reported the efforts were successful on some level. Comments from respondents on how to communicate successfully with the public include providing the public with information and an explanation of why the road is being consid- ered for conversion (safety and cost), transparency about fund- ing, and current and future road conditions. Of the 48 agencies that responded, 22 indicated they would use similar methods for future road conversion projects. KEY OBSERVATIONS FROM INITIAL SURVEY Road conversions from paved to unpaved surfaces identi- fied from the literature, survey, and interview responses have occurred in at least 27 U.S. states (Figure 9) and in other coun- tries (Canada and Finland) (Canfield 2009; Cameron 2010; Etter 2010; Louwagie 2011). Of the 139 survey responses from local, state and province, and federal roads agencies, 48 indicated that they have converted a road or road segment from paved to unpaved and nine that they are considering a road conversion project, whereas 82 indicated they have not converted any paved roads to unpaved. Based on survey responses alone, more than 550 mi of paved roadways in the United States and Canada have been converted to unpaved, with most local road agencies converting an average of 10 mi (range of 0.5 to 30 mi). Many of the 48 survey respondents who have done con- versions transformed an original pavement that was in poor condition to an unpaved surface that was considered to be “good” or “fair.” Responses included asphalt concrete in poor condition (28), asphalt surface treatment (i.e., chip seal) in poor condition (24), or a combination of pavement types in poor condition (six). The AADT on converted roads typically was low, with more than half of the converted roads having an AADT of less than 100 vehicles, and only one conversion having an ADT of more than 500 vehicles (Figure 10). Once converted, road surfaces were left unpaved by most (41) of the survey respondents, with road surface stabilization incorporated into part of the surface layer used by 19, topi- cal application of dust suppressant used by five, and topical application of asphalt emulsion used by four. In most instances, pavement surfaces were recycled in place using a reclaimer or a ripper on a grader (ideally sizing the material to 1-in. top size). When necessary, additional gravel was added and mixed to supplement existing material, after which the roads were shaped and compacted. Road conver- sions typically were completed by agency staff with agency- owned or rented equipment. The remaining conversions were completed by a contractor. Fifty-four of the 57 survey respondents who had converted or planned to convert a road indicated that the cost of main- chapter three SUMMARY OF SURVEY RESULTS

17 KEY OBSERVATIONS FROM FOLLOW-UP INTERVIEWS This section provides an overview of the responses to follow-up interviews with 19 of the survey respondents (from 18 U.S. states and one Canadian province) who have converted paved roads to unpaved. The interviews were conducted to gather information about the conversion process that was not covered in the survey. Appendix B includes details of the responses, which highlight effective and innovative practices in design, construction, planning, public outreach, and funding. The length of roads converted ranged from 0.2 to 42 mi. Many of the road conversions were conducted by smaller agencies with total centerline roadway miles maintained ranging from 19 mi in a rural Montana county to 3,000 mi for a respondent who supervised many counties in the state FIGURE 9 Shaded areas are U.S. states in which roads or road segments have been converted from paved to unpaved. (Identified from the literature and from survey and interview responses.) FIGURE 10 Summary of ADT on roads converted from paved to unpaved. FIGURE 11 Survey responses on why roads were converted from paved to unpaved.

18 of Minnesota. Operating budgets for these agencies ranged from $56,600 as reported in Musselshell County, Montana, to $40 million as reported by the TxDOT (one of a few state DOTs that maintain the local road system). A total of 57 road conversions were reported in the case examples, and all occurred on low-volume roads. Annual average daily traffic for 37 of the 57 conversions was below 100 vehicles, and AADT on all conversions but one was below 400 vehicles (i.e., the AASHTO definition of a low-volume road). Most of the roads converted were asphalt concrete in poor condition, and roads were converted for a variety of reasons, including the cost of maintaining the road, safety concerns, and public complaints. Interviewees were asked if there was anything that would have been helpful during the conversion process, such as a handbook or presentation, documentation, or other sup- porting materials. The objective of this question was to get practitioners to elaborate on what type of information was lacking on the subject of road conversions. Thirteen of the 19 respondents indicated that a handbook describing various aspects of the conversion process would have been helpful (Figure 12). Practitioners indicated that the lack of available information led many to perform the work with no guidance, sometimes resulting in conversions that did not meet expec- tations or were difficult to perform. Feedback from these respondents indicated that a handbook covering topics such as construction specifications, tactics for public relations, case studies with examples from other agencies, and lessons learned would have been helpful during the conversion pro- cess. Only two practitioners indicated that they would not have found a handbook helpful but acknowledged that they had performed many conversions and had significant experi- ence with the process. Five respondents indicated that a presentation to decision makers and affected individuals would have been helpful before the conversion process. Respondents noted that communicat- ing to the public and government officials about conversions was difficult and that a presentation discussing budget con- straints, detailing the process, and showing examples of suc- cessful conversions from other agencies would have made the conversion process easier overall. Two respondents indi- cated that they would have found a life-cycle cost analysis tool helpful to determine when a road may be considered for conversion. One respondent indicated a research project to reference on the practice would have been helpful. In Linn County, Iowa, road practitioners have implemented a dust control policy that determines the selection of road surfacing based on AADT. They have found this policy to be helpful by placing the determination of conversions on traffic counts, rather than budgets or the decisions of personnel at the agency or a county office. Interviewees were asked if there were any special tools, products, or equipment they found particularly useful in the conversion process. A reclaimer or pulverizer was cited as the equipment of choice by 14 of the 19 interviewees (Figure 13). Many noted that the use of this equipment resulted in a better driving surface and was faster and more efficient than other options. One practitioner noted that the reclaimer must be of appropriate size and weight for the job because an under- powered and undersized reclaimer may not produce satisfac- tory road surfacing material. Other respondents stated they used a motor grader and scarifier to break up already deterio- rated asphalt followed by application of gravel with either a dump truck or a paving machine. FIGURE 12 Interviewee responses concerning the need for supporting material and documents that could aid in conversions. FIGURE 13 Interviewee responses concerning tools and equipment used in roads conversion.

19 Chlorides or enzymes were used for stabilization in 13 of the 19 road conversions. Stabilizers were used to mitigate base deficiencies and stabilize the granular portion of the reclaimed road surface, resulting in better and safer driving surfaces. Some respondents indicated they had not used a sta- bilizer initially during the conversion but, as a result of issues with the roadway, were now experimenting with stabilizers to find the most effective option. One respondent said that the use of an enzyme stabilizer improved the road surface, signif- icantly reduced required maintenance, and is now commonly used for road conversions in that area. Two practitioners rec- ommended caution when using stabilizers because overuse can result in pothole formation similar to deteriorated asphalt, which complicates maintenance. Seven respondents indicated dust suppression products were useful. Five respondents reported use of a chloride- based product for dust suppression, whereas two respondents used asphalt emulsion or waste brine from gas and oil wells. The respondents noted that the use of dust suppressants helped to stabilize the road surface, provided a better driving surface, reduced dust levels, and contributed to gaining public accep- tance of converted roads. To this end, many agencies agreed to more frequent applications on newly converted roads as requested by the road users. One question asked respondents if they could share any successful practices with others considering a road conver- sion. Respondents were encouraged to include suggestions about public relations and construction aspects of conver- sions. Of the 19 interviewees, 14 stressed the importance of public outreach (Figure 14). Two practitioners said the public relations component of the conversion process was more dif- ficult than the actual conversion. In conjunction with public outreach, ten of the respondents indicated that transparency when interacting with the public was crucial to the success of projects. Many respondents indicated that the public was more understanding and willing to accept the idea of a road being converted if they understood the reasoning behind the decision, how the work was going to be performed, and what the road would be like after the conversion. Additional sug- gestions from respondents included making the decision to convert roads based on traffic counts (three), emphasizing safety as a reason for the conversion (two), and allowing resi- dents to perform voluntary dust suppression (two). Suggestions of other successful practices during the con- struction phase of the conversion were provided by 14 of the 19 respondents. Most reiterated that using a reclaimer pro- vided the best road surface and was the only large equipment suitable for performing a conversion (Figure 15). Several respondents (seven) indicated that ensuring the correct ratio of crushed asphalt to granular surfacing material and the appropriate top size of the crushed material (1 in. or less) is important so that the road can still be maintained with a grader or have cobbles (large pieces of crushed asphalt) on the surface that influence ride quality (Figure 16). Supple- menting the existing road materials with additional aggregate, including fines, or changing the depth of reclamation were both techniques that respondents indicated could be used to achieve the proper ratio of granular material to reclaimed asphalt. Two respondents also indicated that proper main- tenance after the conversion was important to gain public acceptance and ensure increased longevity of the road. Two respondents indicated that use of a stabilizer was impor- tant for success, and one respondent noted that conversions are not be performed on roads that do not have appropriate drainage. FIGURE 14 Interviewee responses regarding successful public relations practices in roads conversion. Public Outreach (14) Transparency (10) Use of Traffic Counts (3) Emphasize Safety (2) Voluntary Resident Dust Suppression (2) FIGURE 15 Interviewee responses regarding successful construction practices in roads conversion.

20 The final question asked if interviewees had noticed or experienced any specific engineering issues with the road during the conversion process or with how the road per- formed after. Many respondents indicated that converted roads have performed well and require minimal maintenance. However, many interviewees indicated that getting roads to a point of minimal maintenance required considerable effort, much of which was trial and error. Those who did not use a reclaimer indicated issues with “chunks” of asphalt that were difficult to break up and resulted in an uneven driving sur- face (cobbling). Seven respondents indicated that achieving the correct ratio of granular surface material to asphalt had been difficult and often required further measures to address these issues, including additional passes with the reclaimer or a padfoot roller. Some respondents found that the exist- ing granular surfacing material required additional modifica- tion to provide a suitable driving surface. Five respondents indicated that during the conversion process, they had issues with shaping the road and achieving the proper crown but eventually achieved a road that was easier to maintain than the original deteriorated asphalt surface. Three respondents indicated that addressing base issues was something they either did or should have done, with one respondent indicat- ing that the use of geogrids or geotextiles may be helpful. One respondent indicated that the agency should have completed an initial geotechnical investigation of the roadway. Once the conversion was started, the agency found base material of uneven thickness and identified numerous problems in the road base. Two of the respondents noted that identify- ing the type of traffic that would use the converted road was important because they had “underbuilt” the converted road and had to perform additional maintenance to correct issues related to heavy truck traffic. FIGURE 16 A cobbled road surface (a) and close-up of a piece of reclaimed asphalt greater than 1 in. in diameter, which is creating the cobbled surface (b). (Photos courtesy of K. Skorseth.) (a) (b)

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Converting Paved Roads to Unpaved Get This Book
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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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