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NCHRP 20-7 Proposed Research Needs Statement Submitted by: Highway Safety Performance Committee – ANB 25; Dr. John Milton Human Factors Road Design Guides Subcommittee – AND 10(2); Dr. Samuel C. Tignor Date: July 30, 2014 Title: “Assessment of Varied Interpretations Between HFG Guidelines and CMF” Background/Needs Statement: Today there are two new tools available for planning and designing roads and assessing their safety. They are the “Highway Safety Manual” (HSM) and the “Human Factors Guideline for Road Systems” (HFG). The HSM is for estimating the safety of roadway infrastructure. The HFG is to facilitate safe operational decisions by providing the best factual information and insight on road users’ needs. Together these two documents enable highway planners, designers and traffic engineers to incorporate features to promote the highest level of safety for new or upgraded roadways. Both documents were conceived by TRB standing committees, developed with NCHRP support and are now available to highway planners, designers, and traffic engineers. Crash modification factors (CMF) are an essential component of using the HSM for estimating road safety. They are used as part of the HSM computational process. The FHWA Clearinghouse for CMF has compiled hundreds of CMF for numerous safety treatments and countermeasures. The CMF have been assigned star ratings (in a scale of 1-5) to aid users by rating the methodology used to develop the CMF. This assists users in deciding adequacy of a CMF by for given project applications. In short, they are used to compare various treatments and for helping in the selection of treatments that are best for the given projects. The star ratings are assigned based on the review of research reports and the confidence in the results of the study producing the CMF. Guidelines contained within the HFG are developed based on the soundness of human factors research undertaken on specific safety treatments. Each guideline within the HFG is accompanied by a scale rating, (based in linear steps from “primarily expert judgment” to “primarily empirical data”) showing the soundness of the guideline based on the review of many research reports that address how successfully road users can use the treatment. If insufficient definitive human factor research is available, no guideline is developed or based on that individual topic. The HFG guidelines are accompanied by a short review of the research so the user will have a better understanding of the how the treatment performs and is accepted by the road user. Taken together both the HFG and HSM crash modification factors, collectively, have given the designer, planner, and traffic engineer better information on the performance and user acceptance of given treatments than their safety tool boxes have done previously. While differences can sometimes occur when comparing given treatment CMF and HFG guidelines, it is not a case that either is wrong. It can occur based on when the research for the CMF and the HFG guidelines were actually developed and made available. If the time the respective research was done were years apart, the soundness of the research in the experimental plans, whether the traffic and geometric conditions of the CMF and HFG guidelines were comparable, whether statistical tests were appropriate for the data, and other factors can individually or collective have a big impact on the Star rating and whether a HFG guideline was written are considerations that may explain these differences. The goal of this exploratory research is to determine (1) if safety treatments that differ between what is available in the CMF clearinghouse and the HFG guidelines should be a concern to the designer, planner, or traffic engineer, and (2) how difficult what the issues will be in assessing the two documents for these kinds of conditions. What is sought are recommendations on how these two situations can be best addressed across the entire set of CMF and all of the multiple HFG guidelines. It should be noted item 1 also includes the situation where, for specific safety treatments, there is no Star rating provided but a HFG guideline is provided, or vice versa. Research Objective: The objectives are: (1) to review and screen the basis of the CMF and HFG guidelines to determine if there is a suitable and practical way in which different or missing CMF or HFG guidelines can be identified for safety treatments, and, (2) to make recommendations on how and what the HFG and HSM documents should tell designers, planners and traffic engineers to do in such situations. While the number of these differences between the two approaches may be relatively small, users seek guidance on how to resolve them in selecting project safety improvements/treatments. Work Tasks: The following tasks of this exploratory research is to help (1) understand the potential scope of the problem that may arise in selecting appropriate CMF and HFG guidelines when recommendation differences are detected between the two methods, and (2) provide guidance to designers, planners, and traffic engineers in resolving the differences. It should be noted the HFG guidance is specifically associated with road-user perception and understanding of infrastructure design and operations experienced and the HSM is a quantified safety estimate. 1. Review the procedures used in establishing (1) CMF for the HSM models and (2) how guidelines are selected for inclusion in the HFG. 2. Review the comparability of CMF Star ratings and the research reliability scale used in the HFG. 3. Identify candidate procedures to use when given safety treatment CMF values and HFG recommendations differ sufficiently to place the selection and use of the treatment in question. This includes the case when either of the two approaches do not address given safety treatments. 4. Given the large number of CMF and HFG guidelines that have been developed, identify candidate screening procedures that could be used to identify conflicting safety results. 5. Recommend how frequently CMF values and HFG guidelines for the identical treatments should be reviewed. 6. In cases for given safety treatments when there is a difference in whether there is a CMF provided in the Clearinghouse as compared to a suggested HFG guideline, recommend how designers, planners and traffic engineers might proceed in developing project safety recommendations. Urgency: The HFG and HSM are both gaining recognition and acceptance as essential highway safety tools. About 27 percent of highway fatalities are associated with road and user interaction problems. The problems may be design oversights, inadequate time for proper user decision making, or other similar situations. The HSM and HFG were developed to help road designers, planners and traffic engineers make design and operational decisions that are compatible with road users’ needs and capabilities. This exploratory effort will identify potential approaches in how CMF and HFG guideline differences could be resolved. Both of these documents are being increasingly used daily by highway safety analysts and their continued use is highly desirable. Funding Requested and Time Required: It is estimated that this research will take 18-months to complete and will require no more than $50,000. Contact Person: Dr. John Milton, PE Director, Enterprise Risk Management Washington State Department of Transportation 310 Maple Park Avenue SE Lacey, WA 98503-1147 P.O. Box 47418 Olympia, WA 98504-7418 Phone: 360-704-6363; 360-791-9242 Fax: 360-704-6367 [email protected] Developers of Research Problem Statement: Dr. John Milton, PE Director, Enterprise Risk and Safety Management Washington State Department of Transportation 310 Maple Park Avenue SE Lacey, WA 98503-1147 P.O. Box 47418 Olympia, WA 98504-7418 Phone: 360-704-6363; 360-791-9242 Fax: 360-704-6367 [email protected] Dr. Samuel C. Tignor, PE, ASCE Fellow, ITE Member, and retired FHWA R & D Chair of TRB Human Factors Road Design Guides Subcommittee, AND10(2) 1706 Fairview Avenue, McLean, VA 22101 703-356-1037 [email protected] Thomas Hicks, PE Director of Business Development Century Engineering, Inc. 10710 Gilroy Road Hunt Valley, MD 21031 443-589-2400x1323 [email protected]