Safety Prediction Methodology and Analysis Tool for Freeways and Interchanges (2021) / Chapter Skim
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Pages 363-371
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From page 363... ...
363 APPENDIX A: PRACTITIONER INTERVIEWS This appendix describes the findings from interviews with practitioners on the topic of freeway and interchange safety. The findings were used to identify design and operational elements that have a significant effect on safety and knowledge gaps.
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From page 364... ...
364 TABLE A-1. Demographics of telephone interview groups Expertise Agency Representation FHWA Field Offices State DOT MPO Engineering 4 8 1 Planning 1 1 3 Each interview typically consisted of three parts.
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From page 365... ...
365 A final element of the interview was an interactive session where specific design or operational elements were posed and the interviewees were asked to provide a number indicating the importance of each element. The responses to the questions in Figure A-1 are summarized in the following sections.
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From page 366... ...
366 Level of Analysis Detail The planners and the engineers involved in concept planning described a need to evaluate the entirety of the project, regardless of whether the focus is cost, operations, or safety. Some interviewees indicated that the evaluation should reflect performance of the project over its design life.
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From page 367... ...
367 TABLE A-2. Safety information needs for freeway segments Category Element 1 Rank 2 Roadway Lane width 12 Inside or outside shoulder width 2 Median width 9 Roadside and Safety devices in median Clear recovery distance 13 Side slope 4 Barrier length along embankments 3 Barrier type (say, to less rigid)
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From page 368... ...
368 TABLE A-3. Safety information needs for interchange ramps Category Element 1 Rank 2 Roadway Ramp configuration (diamond, loop; direct, semidirect)
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From page 369... ...
369 TABLE A-4. Safety information needs for interchange ramp terminal Category Element 1 Rank 2 Freeway speed-change lane Left-hand or right-hand ramp 11 Lane length (sensitivity to truck percent, grade, no.
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From page 370... ...
370 Experience in reviewing justification reports indicates that the safety impacts of a proposed access point are often addressed through an assessment of its compliance with approved design criteria. In many instances, capacity improvements made in conjunction with the new access are cited as having an indirect safety benefit through the alleviation of queue spillback or bottleneck.
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From page 371... ...
371 One of the respondents used ISAT in preparation of an interchange justification report. The other respondents used it for environmental evaluations and planning studies.
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