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45 Barriers more frequently cited by agencies than con- ditions (e.g., humidity, temperature, and rainfall) and tractors are a lack of should be identified by future research to facilitate the Mix design methods, selection of the most appropriate in-place recycling Experienced contractors, and process. Agency experience. The use of HIR, CIR, and FDR on roadways with annual The only barrier cited more often by contractors than average daily traffic (AADT) greater than 30,000 may agencies is a lack of project selection criteria. be underused by agencies and overused on facilities with AADT less than 5,000. Subgrade support for equipment needs to be considered. The reasons for the differences GAPS in acceptable traffic levels need to be explored. Research on the maximum FDR recycling depth (i.e., The following information is lacking: lift thickness) is needed so that the desired layer den- sity can be obtained. Well-defined terms for in-place recycling processes The impact of roadway geometry and features needs and materials [e.g., differences between the ARRA further research to identify the reasons for differences definition of "integral overlay" and the use of the same between agency and contractor responses. term by agencies as it applies to cold in-place recycling Specific reasons for contractors' and agencies' climate (CIR) and FDR], preferences need to be explained in future research Weather condition guidance for successful construc- efforts. tion of in-place recycling projects, Using a structural overlay when structural capac- Climate considerations for each recycling project's ity improvement may not be needed requires further long-term performance, research to define the criteria for selecting this option. Quantifiable performance characteristics, The ability of other surface treatments to provide Education and information on how various roadway acceptable surface courses in this circumstance also geometry and other features are handled during in- needs to be explored. place recycling processes, Research is needed to quantify environmental and cost Consistent curing procedures for laboratory prepara- benefits. tion of CIR and FDR mix samples, A well-designed experimental approach to evaluating Consistent compaction procedures for in-place recy- the progression of pavement distresses and the overall cling mixes, decline in the pavement condition index for in-place Emulsion binder specifications that are performance recycling methods is needed to provide reliable life- graded, and cycle cost and life expectancy information. Rapid field tests to determine when CIR mats can be Structural coefficients for CIR and FDR can be better overlaid (e.g., when the moisture content is below 1%). defined and based upon performance testing. RESEARCH NEEDS Specific research needs include Reasons for the lack of use of CIR in the Southern and Southeastern states are likely related to weather con-