Developing a Guide for Quantitative Approaches to Systemic Safety Analysis (2020)

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74 Conclusions and Future Research 5.1 Summary of Findings Highway agencies have traditionally managed their highway safety improvement process by identifying and correcting high-crash locations (“hot-spots”), where concentrations of crashes and/or patterns of crashes were found. Recently, to complement their crash-history-based safety management approach, highway agencies have incorporated a systemic safety management approach within their Highway Safety Improvement Program (HSIP) and other safety programs. The systemic safety management approach focuses on widely implementing proven, low-cost safety improvements across the network at sites with a high potential for target crashes. Agencies also implement a policy-based safety management approach to bring design or operational features of sites up to a specified standards and policies. These three primary approaches to highway safety management (i.e., crash-history-based, systemic, and policy-based) vary in terms of the types, quantity, and quality of data required to carry them out; the types of treatments considered for application; and the types of crashes or safety concerns the transportation agency may address; but to some extent the systemic safety management approach is a hybrid of the crash-history-based and policy-based approaches. Applications of systemic safety management approaches look very different from one agency to the next. In general, highway agencies have used three approaches to implementing systemic safety management: application of FHWA Systemic Tool methodology, application of SPFs using in-house tools, and application of the usRAP methodology using the associated ViDA software. The systemic safety management approach described in the FHWA Systemic Tool is the least complex of the three types of applications and is the most adaptable for agencies with incomplete or poor quality inventory, traffic volume, and/or crash data. With the publication of the HSM and its emphasis on SPFs, several agencies have implementing systemic safety management using SPFs which requires high-quality, robust roadway inventory, traffic volume, and crash datasets for all roads within an agency’s jurisdiction or at least for the roadways an agency is interested in managing using systemic analyses. The most comprehensive existing software that implements a systemic safety management approach using SPFs is the AASHTOWare Safety Analyst software. Actually, Safety Analyst can be used to implement both the crash-history-based and the systemic safety management approaches, but only a few states with Safety Analyst licenses have limited experience using the systemic site selection module since this functionality was only recently added to the software. Application of the usRAP methodology and associated ViDA software is unique in that it is a more defined methodological approach to systemic safety but can be adapted for use within the context of an agency’s needs. Reasons for using a systemic safety approach The potential benefits of implementing a systemic safety management approach include the following:  It can be used in the absence of high-quality historical site-level crash data.  It is proactive because countermeasures can be programmed for implementation at locations that may not have a history of crashes.

75  It helps agencies broaden their traffic safety efforts and consider the potential for future crashes as well as crash history when identifying where to make safety improvements.  It provides the ability to program projects further into the future as projects can be based on the presence or absence of crash contributing factors (i.e., roadway characteristics) that do not change frequently from year to year.  It may be easier to more equally distribute safety funds regionally or across jurisdictions.  It is adaptable based on available data. Data Needs The systemic safety management approach is adaptable based on available data; but its implementation may still be relatively data intensive, potentially incorporating reliable roadway inventory, traffic volume, and/or crash data. When implementing the FHWA Systemic Safety Project Selection Tool methodology, agencies utilize available data sources but may still collect additional data elements to identify crash contributing factors for focused crash or facility types. When implementing systemic safety using SPFs, roadway inventory, traffic volume, and crash data are required for development of agency-specific SPFs and/or calibration of existing SPFs. To implement systemic safety using SPFs, most agencies develop their own in-house tools. If an agency wants to use Safety Analyst to implement systemic safety, this software requires approximately 40 data elements to utilize the full functionality of the software. Most of the “required” data elements are Fundamental Data Elements (FDEs) as designated within the Model Inventory of Roadway Elements (MIRE). Agencies can still use Safety Analyst if they do not have all of the required data elements, but the analyses will be limited to the facility types and network for which all of the required data elements are available. To apply the usRAP methodology and associated ViDA software requires use of over 50 roadway characteristics for individual roadway segments. The primary input data for the usRAP ViDA software can be coded from review of aerial photos and street-level photos of the site using highway agency photologs or web-based mapping tools. One of the strengths of the systemic safety management approach is that it is adaptable based on available data. It is not necessary to have a comprehensive, integrated database of roadway inventory, traffic volume, and crash data to begin implementing a systemic safety management. Agencies could start by understanding the purpose and use of data in the context of systemic safety analysis, and the tradeoffs and opportunities that data provide whether in the use of a ranking methodology based on the presence or absence of a crash contributing factor or a required data element within a software tool. Emphasis would ideally be on developing an initial systemic safety management approach based on available data or data that can be easily collected in the short term, and then priorities can be established to develop a more comprehensive dataset over time for a portion of the network and then expand to other parts of the network. As more reliable data become available, the systemic analytical or methodological approach can evolve over time. This may mean that the full functionality or capabilities of software such as Safety Analyst or usRAP ViDA are not initially realized or that some assumptions are made concerning required input data; but over time, the full functionality and capabilities of software tools could be utilized with expanded and more comprehensive datasets.

76 Funding and Implementation Funding of systemic projects varies among agencies. Some agencies formally split HSIP dollars between traditional hot-spot approaches and systemic safety management approaches. Some agencies allocate funding to specific crash types or countermeasures that will be implemented using a systemic safety management approach. Some agencies do not have a specific funding category for systemic and just work it into existing projects/programs Evaluation Evaluations of systemic safety management programs have been conducted using several approaches, but not all agencies have evaluated the effectiveness of their systemic safety management projects. In some cases, systemic projects have only recently been implemented, and it is too early to evaluate the projects; and in other cases, systemic treatments were implemented with other improvements so it is difficult to evaluate the impact of the systemic treatment. The most common approaches to evaluating the safety effectiveness of systemic treatments include a trend analysis, the simple before-after study approach (with or without traffic volume correction), the shift of proportions method, and the Empirical Bayes before-after study method. In general, the same methodological approaches are being used to evaluate the safety effectiveness of treatments whether the treatments are being implemented as part of a crash- history-based, systemic, or policy-based approach. However, it should be recognized that the current state of practice and knowledge in terms of the evaluation approaches can only provide a limited amount of information concerning the overall effectiveness of safety treatments implemented as part of a systemic safety management approach and to some degree a policy- based safety management approach. With the systemic safety management approach, sites across the network may be improved but may not have any crash history prior to being treated and/or after being treated. Because the evaluation methods either directly or indirectly compare the crash history of sites before and after implementation of treatments, the current evaluation methods can only provide a limited perspective on the overall safety effectiveness of treatments implemented as part of a systemic safety management approach. This becomes more of an issue as the number of sites included in the evaluation that have no crash history prior to being treated increases. 5.2 Lessons Learned Several lessons learned throughout the research are as follows:  Some agencies have fully embraced the systemic safety management approach, while others have not. Communication is key. Implementation of systemic safety projects are most successful when (a) the central office of the highway agency leads the analysis, (b) the public is educated on the purpose and need for systemic safety improvements, (c) a diverse group of safety stakeholders is involved in the process, and (d) as appropriate the county board is involved in the process.  One of the advantages of the systemic safety management approach is that it is adaptable based on available data; however, many agencies are under the impression that it is data intensive. It can be, but it does not have to be. A systemic safety management approach

77 to highway safety would ideally always be data driven, but agencies can start out by developing their systemic safety management approach using available data or data that can be easily collected, and then their systemic analytical or methodological approach can evolve over time as more reliable data become available.  One of the objectives of this research was to define quantitative approaches to systemic safety analysis and distinguish it from other approaches for identifying safety improvements such as the crash-history-based (e.g., “hot-spot”) and policy-based approaches. This research report and other accompanying deliverables try to accomplish this objective by describing the three primary roadway safety management approaches (i.e., the crash-history-based, systemic, and policy-based) in relation to the general six- step roadway safety management process, their intended purpose; the types, quantity, and quality of data required to carry them out; the types of treatments considered for application; and potential advantages and disadvantages. It is also noted that the systemic safety management approach is to some extent a hybrid of the crash-history-based and policy-based approaches. As safety management approaches evolve over time, it is anticipated that the blending of these three safety management approaches will continue to occur.  In most cases, agencies are developing their own internal data management procedures or in-house tools to implement systemic safety management approaches. Although existing software such as Safety Analyst and usRAP ViDA are available to implement systemic safety management, few agencies are using these existing software packages to implement systemic safety management.  The same methodological approaches are being used to evaluate the safety effectiveness of treatments implemented as part of the three primary safety management approaches (i.e., crash-history-based, systemic, or policy-based). 5.3 Gaps in Knowledge and Future Research Needs Several related gaps in knowledge identified throughout the research include:  In general, the same methodological approaches are being used to evaluate the safety effectiveness of treatments implemented as part of the three primary safety management approaches (i.e., crash-history-based, systemic, or policy-based). However, the current state of practice and knowledge of the existing evaluation approaches can only provide a limited amount of information concerning the overall effectiveness of safety treatments implemented as part of a systemic safety management approach, especially as the number of sites included in the evaluation that have no crash history prior to being treated increases. New statistical methods will ideally be explored to estimate the effectiveness of safety treatments in the absence of observed crashes, prior to treatment implementation.  Agencies often rely on local data to determine crash contributing factors for certain crash types and facility types. More research is needed on the selection and application of crash contributing factors for a range of crash types and facility types.  Software could be developed for agencies to efficiently implement procedures described in the FHWA Systemic Safety Project Selection Tool.