The Objective of the Project Is to Develop Guideless That Constitute a Protocol for The

RESEARCH PROBLEM STATEMENT

Title: Guidelines for Development HSM Part C Predictive Method Chapters (Potential Research to be Performed Under NCHRP Project 20-7)

Objective and Scope

The objective of the project is to develop guideless that constitute a protocol for the development of predictive method chapters for Part C of the AASHTO Highway Safety Manual. The guidelines should address the format and content of a predictive method chapter. A focus of the guidelines should be on the range of statistical methods considered acceptable for development of HSM predictive methods. The guidelines should set a high standard to assure that HSM predictive methods provide consistent and accurate results, but should not be so rigid as to stifle innovation by researchers developing predictive methods. The guidelines are intended for application by researchers developing HSM Part C chapters and researchers responsible for production of the second edition of the HSM and subsequent editions. The guidelines should be presented in an appropriate document for future research sponsors to specify as a protocol to be followed in future research projects to develop or revise HSM Part C chapters.

Description of Work to be Performed

The guidelines to be developed in the research shall address:

 Desired outline of a typical HSM Part C chapter  Format guidelines for HSM Part C chapters (refer to latest guidance from AASHTO publications staff)  Structure of predictive method [including safety performance functions (SPFs), crash modification factors (CMFs), and calibration factors]  Development of SPFs, including appropriate statistical methods  Crash severity levels to be considered and methods for incorporating consideration of crash severity levels  Crash types to be considered and methods for incorporating consideration of crash types  Development of CMFs, including appropriate statistical methods  Calibration factors and calibration procedure  Procedures to incorporate observed crash frequencies together with model predictions (e.g., the Empirical Bayes method)  Sample problems  Manual worksheets  Spreadsheet tools and or software

In developing guidelines and protocols, the research team shall review and consider previous work related to the development of HSM Part C chapters, including work performed in:  NCHRP Project 17-18(4), Highway Safety Manual (which included development of the prototype chapter, a first draft of HSM Chapter 10)  NCHRP Project 17-26, Methodology to Predict the Safety Performance of Urban and Suburban Arterials  NCHRP Project 17-29, Methodology to Predict the Safety Performance of Rural Multilane Highways  NCHRP Project 17-36, Production of the First Edition of the Highway Safety Manual  NCHRP Project 17-45, Enhanced Safety Prediction Methodology and Analysis Tool for Freeways and Interchanges  NCHRP Project 17-54, Consideration of Roadside Features in the Highway Safety Manual

The research team shall consider inclusion of guidance from:

 NCHRP Recommended Protocols for Developing Crash Modification Factors  FHWA Guide for Developing Quality Crash Modification Factors  FHWA SPF development guidelines (currently under development)

During the research, the research team shall coordinate with ongoing research in:

 NCHRP Project 15-58, Safety Prediction Models for Six-Lane and One-Way Arterials  NCHRP Project 17-62, Improved Prediction Models for Crash Types and Crash Severities  NCHRP Project 17-63, Guidance for the Development and Application of Crash Modification Factors and should consider any new concepts for SPF and CMF development from those projects.

As meeting schedules dictate, the research team shall convene either two separate workshops or one combined workshop with the Task Group on Technical Publications Oversight and Outreach of the AASHTO Safety Management Subcommittee and the TRB Highway Safety Performance Committee to discuss the content of the guidelines document. Input from the AASHTO Standing Committee on Highways Subcommittees on Design and Traffic Engineering will be obtained through their members on the Safety Management Task Group. In these workshops, the research team shall encourage the AASHTO Task Group and TRB Committee to discuss and debate a range of potential approaches for developing various aspects of the predictive methods and shall lead these groups toward the development of a consensus on these issues that can be incorporated in the protocol. Where consensus is reached in the workshop with the AASHTO and TRB groups, that consensus shall be reflected in the draft protocol. Where consensus is not reached in the workshop, the research team shall follow up by providing a memorandum presenting specific alternative approaches for review by the AASHTO Task Group and TRB Committee and shall ask the AASHTO Task Group and the TRB Committee to consider and assess the alternatives presented.

The research team shall review and consider any HSM user feedback and comments on HSM Part C that have been received by the AASHTO Task Group and the TRB Committee since the publication of the first edition of the HSM.

The primary deliverable from the research will be document presenting guidelines and protocols for the development of HSM Part C predictive method chapters. This document shall be submitted initially in draft form for review by the NCHRP panel, as well as review by the AASHTO Task Group and the TRB Committee. The draft document shall be revised in response to the comments received from all reviewers and shall be submitted in appropriate form for potential publication by NCHRP or AASHTO.

Funding Level and Period of Performance

$75,000; 12 months

AASHTO Staff Contact

Kelly Hardy, [email protected]