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Suggested Citation:"Chapter 2 - Research Approach." National Academies of Sciences, Engineering, and Medicine. 2010. Recommended Procedures for Testing and Evaluating Detectable Warning Systems. Washington, DC: The National Academies Press. doi: 10.17226/22937.
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Suggested Citation:"Chapter 2 - Research Approach." National Academies of Sciences, Engineering, and Medicine. 2010. Recommended Procedures for Testing and Evaluating Detectable Warning Systems. Washington, DC: The National Academies Press. doi: 10.17226/22937.
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Suggested Citation:"Chapter 2 - Research Approach." National Academies of Sciences, Engineering, and Medicine. 2010. Recommended Procedures for Testing and Evaluating Detectable Warning Systems. Washington, DC: The National Academies Press. doi: 10.17226/22937.
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Page 8

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6Summary of Tasks The research approach consisted of two distinct phases. Phase I consisted of a review of available literature and infor- mation available from transportation agencies, the definition of long-term performance and durability requirements, the identification of properties that influence long-term durability, the identification of test methods currently used to evaluate these properties (if available), and the design of a test protocol for evaluating durability of detectable warnings. Phase II consisted of development and refinement of the test methods, development of guidance on the use of these test methods, preparation of these test methods in a format suitable for consideration and adoption by AASHTO, and preparation of this final report. Phase I Approach The efforts of Phase I focused on collecting and reviewing relevant information that formed the basis for this protocol development. The first part of the Phase I effort consisted of reviewing the available literature regarding the durability of detectable warning systems and reviewing the available liter- ature and manufacturers’ product data for test methods used on detectable warning systems and materials. This included a survey of local and state DOTs seeking information related to experiences with detectable warning systems and perceived deterioration mechanisms. The Transportation Research Information Service (TRIS), National Technical Information Service (NTIS) and the Research in Progress site at the Transportation Research Board website have been extensively searched. In addition, an inde- pendent search for additional publications related to durability studies was conducted. Most of the pertinent information identified and reviewed is in the form of reports by state DOTs, as well as two published reports synthesizing earlier work and providing additional information on durability concerns collected from state and municipal DOTs. To gather additional experiences and identify concerns of transportation professionals about long-term performance and durability requirements, a questionnaire prepared by the research team was submitted to state and municipal DOT rep- resentatives. The questionnaire requested information about the respondent’s perceptions, problems, and experiences with the durability of detectable warning systems. In addition to direct submission to representatives of the 50 states, the ques- tionnaire was submitted directly to approximately 30 other contacts and was posted on the FHWA’s Highway Commu- nity Exchange Detectable Warning Discussion site, found at http://knowledge.fhwa.dot.gov/cops/hcx.nsf/home?openform &Group=Detectable%20Warnings. From this information and the experience of the research team, the mechanisms of deterioration of detectable warning systems were determined, the suitability of standard test meth- ods was evaluated and a test protocol for evaluating durability of detectable warnings was designed. Phase II Approach The objective of this phase was to develop and refine the proposed testing protocol consisting of individual exposure and evaluation tests suitable for evaluating durability of detectable warning systems. The testing protocol has been developed with the following objectives in mind: • The protocol evaluates detectable warning systems that have been attached to concrete slabs to test the durability of the installed system, while considering the interaction of the detectable warning system with a concrete substrate. • A cyclic exposure protocol has been proposed to test the interaction of various exposure regimes. The exposures will by cycled to evaluate the interaction. • The protocol is not product-specific; all tests are applica- ble to all types of detectable warning system materials and attachments. C H A P T E R 2 Research Approach

7The durability of detectable warning systems is inextricably tied to the interaction between the system and the concrete sidewalk to which it is applied or anchored, the exposures and evaluation tests were conducted on detectable warning systems installed in concrete slabs to appropriately simulate the field response under the applied exposure conditions. The test protocol consists of exposing systems to specific physical and environmental regimes and evaluating responses to these regimes with a series of performance evaluation tests. Exposure regimes will simulate the effects of outdoor exposure, while the evaluation tests are used to assess durability and performance of the detectable warning systems. Exposure regimes include freeze/thaw, high temperature thermal cycling, ultraviolet light exposure, and abrasion exposure. Evaluation tests include: visual and microscopic evaluation, color measure- ment, dome shape and geometry measurement, slip resistance, coating and single dome bond, resistance to impact from falling tup, wear resistance, and resistance to impact from simulated snowplow blade. The exposure regimes are intended to be combined and performed cyclically to simulate the effects of outdoor expo- sure, where exposure-related deterioration mechanisms act simultaneously. Environmental exposure leads to progressive deterioration; the effects of one type of exposure will build upon the effects of other types of exposure to produce overall greater deterioration than expected from simple additive effects. Two exposure categories (“hot” and “cold”), based on climatic conditions, have been developed. Schematics of the two expo- sure categories showing the cyclic exposure are provided in Figures 2 and 3. Evaluation tests are laboratory procedures that test a spe- cific property or quality of the detectable warning system. These tests may be performed on specimens before exposure and will be performed after exposure. The results of the tests conducted after exposure may be compared to the results from the as-fabricated specimens to determine durability of the product. These test results may also be compared to a set of minimum standards (which may be set by individual DOTs or by future legislation) to determine suitability of the product. Test Method Development The literature review and survey of state and municipal agencies identified specific needs relative to the development of a procedure for evaluating durability of detectable warning systems. Each individual exposure and evaluation test method has been developed with the following objectives in mind. The standardized test methods need to be repeatable so that the data obtained can be compared with the results of other tests run according to the same method. The methods have been written to be implemented in any laboratory that has or can fabricate the basic facilities and equipment required. Where possible, existing standard test methods were used or adapted; however, most methods developed for this program could not adequately draw on an existing method. For each newly developed test, the equipment is defined in sufficient detail so that it could be obtained or fabricated. Finally, the test methods were developed with a goal of being representative of field exposure. Studies of field exposure were not included in this project, although the experience of the research team and the literature review and results of the survey provided insight as to the degradation mechanisms and lifetimes of some detectable warning systems. The test protocol consists of a governing master test method that details the preparation of concrete slabs and attachment of the detectable warning systems and references the exposure methods designed to expose specimens to specific deteriora- tion mechanisms and evaluation test methods for evaluating specific properties of the detectable warning systems before or after exposure. The applicable physical phenomena likely to cause deterioration of detectable warning systems are rep- High-Temp Thermal Cycling Abrasion Ultraviolet Figure 2. Cycle of exposure regimes for the hot exposure category. High-Temp Thermal Cycling AbrasionFreeze/Thaw Ultraviolet Figure 3. Cycle of exposure regimes for the cold exposure category.

8resented by four exposures and nine evaluation methods. Equipment to perform these methods was designed, built, and used to conduct these tests on samples representing the range of detectable warning systems that are currently commercially available. Based on the experience gained during this effort, the testing procedures were refined. Sample Selection Based on the literature review and survey of transportation professionals, commonly available detectable warning systems were classified into types by their material (metallic, flexible polymer, rigid polymer, etc.) and the attachment mechanism. Two attachment mechanisms predominate: cast-in-place, where the detectable warning system is cast into freshly placed plastic concrete, and surface applied, where the detectable warning system is applied to fully cured concrete. Cast-in- place systems are often used in new construction, while surface- applied systems are often used for retrofitting existing walkways. The seven specimen types selected for use in the test method development phase are provided in Table 1. Specimens were obtained from suppliers that were selected, in part, to represent commonly used brands based on the liter- ature review and survey, although the brands represented are not necessarily the most commonly used. Material Type Installation Method Rigid polymer composite panel Cast-in-place Rigid polymer composite panel Surface-applied Flexible polymer panel Surface-applied Metal panel Cast-in-place Polymer concrete panel Cast-in-place Single domes Surface-applied Precast concrete paver Paver--thin set mortar Table 1. Specimen types selected for use in test method development.

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TRB’s National Cooperative Highway Research Program (NCHRP) Report 670: Recommended Procedures for Testing and Evaluating Detectable Warning Systems explores a set of recommended test methods for evaluating the durability of detectable warning systems. These methods address exposure regimes, test procedures, and evaluation criteria to help select detectable warning systems that provide long-term performance and durability while meeting the requirements of the Americans with Disabilities Act Accessibility Guidelines.

The appendix contained in the research agency’s final report provides further elaboration on the work performed in this project. This appendix titled Research Leading to the Development of Methodology for Durability Assessment of Detectable Warning Systems is available online.

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