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69 CHAPTER 4 â SURVEY OF PRACTICE A survey was conducted to determine Transportation Agency plans for implementing NCHRP Report 656 and to identify damage modes and other system elements (e.g., wood posts, transitions, end treatments) that should be added to those covered by Report 656. This information was considered important for several reasons. First, it was essential to understand the issues facing the user base of the Field Guide. Additionally, it was essential to understand what obstacles users have or may face when implementing the research recommendation into practice. The survey had two target audiences (1) those with direct maintenance responsibilities in the state DOTâs and (2) those involved in barrier design and evaluation. The two groups have very different perspectives on the performance of these systems, but only the maintenance group is able to provide feedback regarding the usefulness of the field guide. In particular, only certain entities in the DOT maintenance groups have reasonable knowledge of the existence of Report 656 and whether its recommendations have been implemented in their stateâs maintenance practices. Two separate surveys were developed and sent to the two groups with survey questions designed according to eachâs respective field and expected knowledge base. Survey 1 was designed to target maintenance engineers with the states and providences; therefore the survey was sent to the member list for the AASHTO Subcommittee on Maintenance which included 104 members on their email list. Survey 2 was designed to target researchers and policy makers familiar with ongoing and recently completed research in this field. The second survey was sent to the chair of TRB AFB20 to forward to the TRB AFB20 âcommittee members and friendsâ list. It was not known exactly how many people were on this list but the number was likely in the many hundreds. The surveys were assembled and made available using the on-line tool surveymonkey.com (i.e., www.surveymonkey.com). The advantage to using an internet-based facility like Survey Monkey was that very sophisticated surveys can be developed and easily disseminated to recipients by email. The intent of the two surveys was to analyze the unique perspectives from these separate functional fields (i.e., maintenance and research); however, since the TRB AFB20 committee and subcommittees encompass many professional groups, the respondents to Survey 2 included a significant proportion of maintenance engineers, as well as researchers, policy makers, manufacturers and others. Therefore, where appropriate the results of the two surveys were combined and reorganized into two profession groups: (1) Maintenance and (2) Research/Policy/Other. The results of the surveys are presented in Appendix B. Unfortunately, the response rate on the survey was relatively low with a total of only 29 respondents. Twenty of the respondents were involved in maintenance related fields, and nine respondents were involved in research/policy/other. The survey results (see Appendix B) are presented graphically and include the average response from each of the two individual groups, as well as, the overall average response of the combined groups. The questions included (but were not limited to): ï· What types of barrier should be included in the study, ï· What types of damage modes are most common for each barrier type,
70 ï· What types of damages are associated with each specific component of the barrier, ï· What combination of damage modes are typical of crash damaged guardrail and which of those damage combinations should be considered for this study. The two groups generally agreed on questions related to the G4(2W) wood-post guardrail and the standard thrie-beam guardrails, which are both widely used systems; but often disagreed on the answers to questions related to the modified thrie-beam and the weak-post w-beam guardrail systems. It was assumed that these differences were due to the different perspectives of the two groups; however, it was also possible that there was confusion regarding those two particular guardrail systems. For example, as shown in the Background section, the blockout on the standard G9 thrie-beam guardrail was changed to a wooden blockout in the late 90âs to improve crash performance, thus some respondents may have considered the wood-block thrie- beam system to be a modified thrie-beam guardrail. Likewise, the weak-post w-beam guardrail, which is a TL-3 system very common throughout the northeastern States, may have been confused with other so-called âweak-postâ systems that use standard strong-posts (i.e., W6x9 steel posts or 6x8-inch wood posts) with wider post spacing (i.e., 12.5-ft post spacing) and no blockouts. These so-called âweak-postâ systems are very common throughout the country but are generally installed on low-speed roadways since they are rated as TL-2 or lower. It was also possible that respondents from the research field may have rated damage modes based on their perceived âeffect on performanceâ rather than how common the damage mode was for the system. For example, in almost every case the research/policy/other group gave higher ratings for damage modes, regardless of system, compared to the maintenance group. Overall, the results of the survey were not too surprising. With such a low number of respondents it was not clear, however, how much merit could be given to the results. Where appropriate, the results of the survey in combination with the information garnered from the literature review were used for prioritize of the guardrail system(s) and damage modes considered for investigation in this study.
