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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2021. Safety Performance of Part-Time Shoulder Use on Freeways, Volume 1: Informational Guide and Safety Evaluation Guidelines. Washington, DC: The National Academies Press. doi: 10.17226/26394.
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Page 20

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20 P A R T - T I M E S H O U L D E R U S E S A F E T Y E V A L U A T I O N G U I D E L I N E S Summary One of the objectives of National Cooperative Highway Research Program (NCHRP) Project 17-89, Safety Performance of Part-time Shoulder Use on Freeways, was to “develop quantitative tools for practitioners to use to evaluate safety performance of freeways with part-time shoulder use as a function of temporal, operational, and other conditions when the shoulder is open or closed to traffic.” To address this objective, crash prediction models for freeways with part-time shoulder use (PTSU), suitable for inclusion in a future edition of AASHTO’s Highway Safety Manual (HSM), were developed. This document presents (1) an overview of the crash prediction models, (2) draft text for a future edition of the HSM, (3) information on a spreadsheet tool that implements the crash prediction models, and (4) a discussion of understanding results from the crash prediction model. A separate document, the PTSU Informational Guide, discusses findings obtained from models, such as the magnitude of crash frequency changes associated with the implementation of PTSU on freeways.

Next: Chapter 1 Crash Prediction Model Overview »
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Left or right shoulders can be strategically opened as travel lanes, and "part-time shoulder use" is defined as using a shoulder "some, but not all, hours of the day.”

The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 309: Safety Performance of Part-Time Shoulder Use on Freeways, Volume 1: Informational Guide and Safety Evaluation Guidelines provides an overview of part-time shoulder use, presents the results of past operational studies, and presents the results of safety research conducted through NCHRP's Safety Performance of Part-time Shoulder Use on Freeways project.

Supplemental to the document is a Freeway Analysis Tool, which includes BOS data, S D PTSU Data, and a Prediction Tool, as well as NCHRP Web-Only Document 309: Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report.

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