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11 CHAPTER TWO SUMMARY OF INFORMATION COLLECTED INTRODUCTION no effort was made to survey these agencies, as it was beyond the scope of this synthesis. Finally, the reader must under- This report is the result of a comprehensive literature review, stand that because the survey results are presented in tabular a survey of both U.S. and Canadian public highway agencies, form throughout the report that attempting to add up the vari- a content analysis of DOT microsurfacing specifications, and ous responses and get them to sum to the same number for the case studies of DOT-specific experiences with microsurfac- United States and Canada cannot be done. Many of the ques- ing. The resulting information is merely a recitation of infor- tions asked respondents to check all answers that applied. A mation found by each of those instruments and conclusions number of the questions were follow-up questions answered drawn are based on multiple confirmations from two or more only by those respondents that answered in a prescribed man- study instruments. It must be noted that the synthesis repre- ner on the previous questions and some of the surveys were not sents a "snapshot" in time with respect to the state of the prac- totally completed. Therefore, the survey results are reported tice. Wherever possible, seeming conflicts between survey exactly as they were observed. responses and other information, such as the literature, were verified by a third source. However, when no conflict arose, Standard microsurfacing specifications from all 50 U.S. the information reported in the survey was accepted and car- states plus the District of Columbia and the FHWA Federal ried into the analysis. Lands Highway Division (FLHD) were assembled. Of that group, 18 contained sections that specifically contained the SYNTHESIS METHODOLOGY word "microsurfacing." The others may have been used for microsurfacing under another term such as "surface treat- The synthesis employed the following major study instruments: ment" or even "slurry seal." Other section titles found were: "Cold-Laid Latex Modified Emulsion Pavement 1. Comprehensive literature review, Course" (Pennsylvania) and "Paver-laid Surface Treatment" 2. Survey of U.S. state and Canadian province transporta- (Alabama). An example of the indeterminate state of micro- tion agencies, surfacing terminology is the FLHD specification, which states 3. Content analysis of U.S. microsurfacing specifications, in Section 410--Slurry Seal: "This work consists of applying and an asphalt slurry seal or a polymer modified microsurfacing 4. Case study analysis of selected U.S. and Canadian mix on an existing pavement surface" (FLHD 2003, italics microsurfacing programs. added). The word "microsurfacing" is found only in this sen- tence and the remainder of the section does not differentiate The structure and content of each of the instruments was between the two treatments, effectively giving both treatments developed to integrate with all other instruments, which allows the same specification. As a result of the potential for inaccu- the output of each instrument to be mapped with the output of rate analysis, only the 18 specifications that contained a refer- the others identifying trends in the data. ence to microsurfacing were included in the content analysis. The survey was issued to the maintenance engineers in A case study analysis was also undertaken to furnish spe- 50 U.S. state DOTs and 13 Canadian provincial or territorial cific information on microsurfacing as experienced by selected MOTs (see Appendix A for details). A survey on microsurfac- agencies. Each case study was selected for a specific focus, ing practices provided responses from 44 U.S. state DOTs and which furnishes a unique perspective on an agency's micro- 12 Canadian provincial MOTs, resulting in an overall response surfacing program. Table 4 shows the case studies and the rea- rate of 89%. The survey respondents are shown in Figure 4. son each was selected. This analysis separated the U.S. and Canadian responses to account for the difference in the construction contracting reg- GENERAL AGENCY MICROSURFACING ulatory environment that exists in both countries and also to INFORMATION highlight potential innovative Canadian microsurfacing prac- tices, keeping them from being lost in the total survey popula- To put the information in this report in proper context, the tion. It can be noted that local agencies at the municipal and reader needs to understand the relative magnitude of micro- county levels are also known to use microsurfacing. However, surfacing programs in the United States and Canada. Table 5
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12 FIGURE 4 Survey responses from U.S. DOTs and Canadian MOTs. TABLE 4 CASE STUDY SUMMARY Agency Reason for Inclusion Georgia DOT Agency with successful demonstration project but does not use in program. Also included road noise analysis. Kansas DOT Microsurfacing on jointed concrete pavement. Maine DOT Agency uses microsurfacing to maintain both roads that are built to DOT standards and roads that are not built to DOT standards. Minnesota DOT Agency has robust internal microsurfacing research program, including trials of softer binders to reduce cracking. Oklahoma DOT Agency has 9-year field performance monitoring program and an ongoing rigorous field test that focuses on microsurfacing skid resistance and macrotexture. Ontario MTO Agency has completed rigorous studies relating microsurfacing to traffic safety. TABLE 5 SUMMARY OF MICROSURFACING PROGRAM STATISTICS FROM SURVEY RESPONDENTS Characteristic U.S. DOT Canada Percent of Rural Local Roads with Microsurfacing 2.2% 0.0% Percent of Rural Interstate Roads with Microsurfacing 5.6% 9.1% Percent of Urban Local Roads with Microsurfacing 6.0% 0.0% Percent of Urban Interstate Roads with Microsurfacing 10.7% 0.3% Percent Total Network with Microsurfacing 3.1% 6.9% Average Microsurfacing Approximate Annual Volume $3.0 million $4.0 million* High Reported $12.0 million $10.0 million* Low Reported $0.5 million $0.06 million* Average Microsurfacing Annual Program Size 60 miles (96.6 km) 57 miles (92 km) High Reported 150 miles (241.4 km) 124 miles (200 km) Low Reported 12 miles (19.3 km) 10 miles (16 km) Agencies with Microsurfacing Installed by In-house Crews 1 2 Agencies with Microsurfacing Installed by Contractor Crews 30 6 *These are Canadian dollars, which at the time of this writing is trading at roughly par to the U.S. dollar.