Aligning Geometric Design with Roadway Context (2022) / Chapter Skim
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Pages 57-61
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57 Chapter 3: Future Suggested Research NCHRP Project 15‐77 developed Draft Part IV (Facility Design in Context) Chapters suitable for direct use in a future project to develop the GB8. As discussed throughout this project, the Draft Part IV content is expected to evolve and be refined when developing other GB8 Parts. In addition, the research team identified areas of further research that would provide additional benefit to this topic area but could not be included within the scope of NCHRP Project 15‐77. The following list provides a summary of suggested future research related to geometric design for roadway context. Speed: There continues to be discontinuity and ambiguity in concepts and applications of the term "speed." Research is needed to expand upon past speed concepts and understand the role of target speeds in relation to design and posted speeds. It is still not uncommon for agencies to establish design speeds 10 mph higher than the anticipated posted speed as a "safety factor." In fact, this practice leads to roadways that promote speed that can degrade safety performance. It can lead to establishing new posted speeds based on measured 85th percentile speeds. NCHRP Project 15‐76 Designing for Target Speed is venturing into the area of considering designing for target speed while NCHRP Project 17‐76 Guidance for the Setting of Speed Limits will provide guidance on establishing roadway speed limits. There are opportunities to tie existing and new speed related guidance to better support roadway planning and design decisions related to Part IV of Green Book 8 (Designing in Context)
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58 providing a user guide and tool to make informed decisions related to establishing speed limits on roadways. It investigated factors that influence operating speed and safety through a review of the literature and an analysis of the relationships for speed, safety, and roadway characteristics on urban/suburban streets.
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59 measures that could be based on the same fundamental topic. A common project purpose and need is to "improve traffic flow, reduce congestion, and improve safety performance." While the Highway Safety Manual allows us to quantify safety performance, it may not be usable for all roadways or specific project conditions.
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60 o Based upon the feasibility of conducting performance estimation in project development context (e.g., data requirements, data availability and accuracy, required level of human expertise and effort) , and o Used and applied considering the accuracy and reliability of the prediction technique(s)
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From page 61... ...
61 intersections. Trucks serving long-distance freight needs may pass along suburban roadways on their way to freeway interchanges.
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