National Academies Press: OpenBook

Guide for Quantitative Approaches to Systemic Safety Analysis (2020)

Chapter: Section 4 - Selecting the Appropriate Systemic Safety Management Approach and Software Tool

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Suggested Citation:"Section 4 - Selecting the Appropriate Systemic Safety Management Approach and Software Tool." National Academies of Sciences, Engineering, and Medicine. 2020. Guide for Quantitative Approaches to Systemic Safety Analysis. Washington, DC: The National Academies Press. doi: 10.17226/26032.
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Suggested Citation:"Section 4 - Selecting the Appropriate Systemic Safety Management Approach and Software Tool." National Academies of Sciences, Engineering, and Medicine. 2020. Guide for Quantitative Approaches to Systemic Safety Analysis. Washington, DC: The National Academies Press. doi: 10.17226/26032.
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Suggested Citation:"Section 4 - Selecting the Appropriate Systemic Safety Management Approach and Software Tool." National Academies of Sciences, Engineering, and Medicine. 2020. Guide for Quantitative Approaches to Systemic Safety Analysis. Washington, DC: The National Academies Press. doi: 10.17226/26032.
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Suggested Citation:"Section 4 - Selecting the Appropriate Systemic Safety Management Approach and Software Tool." National Academies of Sciences, Engineering, and Medicine. 2020. Guide for Quantitative Approaches to Systemic Safety Analysis. Washington, DC: The National Academies Press. doi: 10.17226/26032.
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Suggested Citation:"Section 4 - Selecting the Appropriate Systemic Safety Management Approach and Software Tool." National Academies of Sciences, Engineering, and Medicine. 2020. Guide for Quantitative Approaches to Systemic Safety Analysis. Washington, DC: The National Academies Press. doi: 10.17226/26032.
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Suggested Citation:"Section 4 - Selecting the Appropriate Systemic Safety Management Approach and Software Tool." National Academies of Sciences, Engineering, and Medicine. 2020. Guide for Quantitative Approaches to Systemic Safety Analysis. Washington, DC: The National Academies Press. doi: 10.17226/26032.
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Suggested Citation:"Section 4 - Selecting the Appropriate Systemic Safety Management Approach and Software Tool." National Academies of Sciences, Engineering, and Medicine. 2020. Guide for Quantitative Approaches to Systemic Safety Analysis. Washington, DC: The National Academies Press. doi: 10.17226/26032.
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54 Selecting the Appropriate Systemic Safety Management Approach and Software Tool As described in previous sections of this document, there are a number of systemic safety management approaches and software tools available to help agencies implement a systemic safety management program. Deciding which systemic safety management approach and/or software tool to use depends on several factors, including: • Which step in the processes the agency is focused on. Some agencies may come into the process with a blank slate, needing to identify the focus crash types, facility types, and contributing factors in order to then select countermeasures. Other agencies may have already identified crash types, facility types, and countermeasures and need tools for project prioritization. • The availability and reliability of crash data. One of the advantages of implementing a systemic safety management program is that location-specific crash data are not necessarily needed. However, for one of the systemic safety management approaches and software tools, reliable crash data are required. • The availability and reliability of roadway inventory data. To determine where best to implement systemic projects, roadway inventory data are needed to first identify which roadway features are associated with the highest numbers of crashes and second, where certain countermeasures are likely to be the most appropriate for installation. For example, without accurate information on the location of shoulder rumble strips, it will be difficult to know which locations on the roadway network should have rumble strips added. • The ability to develop and apply planning-level SPFs. SPFs give agencies the ability to predict the number of crashes along certain roadway segments and at intersections based on the facility type and traffic volume. SPFs may also include variables for specific roadway elements and conditions, but these are generally project-level SPFs rather than planning- level SPFs. Some agencies have already developed SPFs that can be used to implement a systemic safety management program. Other agencies may choose to develop them or to partner with a university or consultant with the technical expertise to develop them. In some cases, the development of SPFs may be too costly. Some agencies may choose to calibrate existing SPFs developed by others. • The extent and type of roadway system being evaluated. City- or county-level systemic safety management often requires a different approach than state-level systemic safety because these networks often have differences in their mix of facility types, available and reliable data elements, the types of countermeasures that can be considered, and the number of projects that can be completed. In addition, states are more likely than cities or counties to have a robust safety plan in place with target crash types (and sometimes facility types and contributing factors) already identified. • The amount of time and resources available to develop the systemic safety project plans. Implementing a systemic safety management approach can range from a fairly simplistic S E C T I O N 4

Selecting the Appropriate Systemic Safety Management Approach and Software Tool 55 analysis and project prioritization based almost entirely on data from crash reports and published information about treatment effectiveness to a detailed, agency-specific, data- driven approach. • The role of systemic safety in the agency’s overall safety management program. Agencies that want to shift a substantial amount of safety planning from crash-history-based and policy-based programs to a systemic program might be more willing to invest the time and resources required to apply a systemwide software tool such as Safety Analyst or usRAP. These software tools require the development of an input database to run the analyses, and the results are more scientifically based and backed by research. These software tools can provide suggested safety projects for a number of roadway types, crash types, contributing factors, and countermeasures, rather than requiring the user to identify the focus areas and performing individual analyses for each combination. On the other hand, agencies first exploring systemic analysis may choose instead to start with a specific combination of crash type, facility type, and contributing factors to prioritize locations for implementation of one or more specific countermeasures. This section presents a series of questions to assist agencies in selecting a systemic safety management approach and potential software tool that will best help them meet their systemic safety program goals and needs. The questions will help an agency assess its needs, data, and resources, which will then guide the agency toward a recommendation for selecting a preferred systemic safety management approach and/or software tool for implementation. The systemic safety management approaches and software tools addressed in this series of questions and guided recommendations include: • Application of the FHWA Systemic Tool methodology, • Application of systemic safety management using SPFs, • Application of systemic safety management using usRAP ViDA software, • AASHTO Safety Analyst software, and • Development of in-house tools to implement systemic safety management using SPFs. Figure 5 illustrates the logic and framework of the questions geared toward helping an agency select a preferred systemic safety management approach and/or software tool for implementation.

Figure 5. Logic and framework geared toward helping an agency select a preferred systemic safety management approach and/or software tool for implementation.

Selecting the Appropriate Systemic Safety Management Approach and Software Tool 57 Q 1. Does your agency have reliable crash data for your entire roadway network or portions of the network? a. Response: Yes. If the answer is yes, then your agency has the option of imple- menting any of the systemic applications (i.e., application of the FHWA Systemic Tool methodology, application of SPFs, and application of the usRAP methodology and ViDA software), your agency can make use of existing software tools (i.e., both Safety Analyst and usRAP ViDA), and your agency has the option to develop in-house tools to implement systemic safety using SPFs. Some agencies include crash data in their network screening ranking methodology when implementing the FHWA Systemic Tool approach. Reliable crash data can also be used to calibrate the usRAP ViDA software when available, and reliable crash data are used to develop and calibrate SPFs when applying systemic safety and the Safety Analyst software. (Go to Question 2A.) b. Response: No. If the answer is no, then application of SPFs and use of the Safety Analyst software are eliminated from consideration because SPFs cannot be developed nor calibrated without reliable crash data, and crash data are required to analyze sites within Safety Analyst. However, application of the FHWA Systemic Tool methodology and application of the usRAP ViDA software are still both potential options for implementing systemic safety management. (Go to Question 2B.) As a general rule, reliable crash data are more readily available for state-maintained roads than for county and local roads. Thus, in most cases, application of SPFs and the use of in-house tools or the Safety Analyst software will not be an option for analyzing and programming systemic projects for county and local roads. Q. 2A. Does your agency have reliable traffic volume data for your entire roadway network or portions of the network? a. Response: Yes. If the answer is yes, then your agency still has the option of implement- ing all three types of systemic applications (i.e., application of the FHWA Systemic Tool methodology, application of SPFs, and application of the usRAP methodology and ViDA software), your agency can make use of existing software tools (i.e., both Safety Analyst and usRAP ViDA), and your agency has the option to develop in-house tools to implement systemic safety using SPFs. Some agencies use traffic volume data in their network screening ranking methodology when implementing the FHWA Systemic Tool approach. Reliable traffic volume data are necessary for application of SPFs, either using Safety Analyst or in-house tools, and the usRAP ViDA software. (Go to Question 3A.) b. Response: No. If the answer is no, then the only remaining alternative is to use the FHWA Systemic Tool methodology to implement systemic safety management. The other systemic applications and software (i.e., Safety Analyst and usRAP ViDA) require reliable traffic volume data for implementation. (Recommendation: Consider using the FHWA Systemic Tool methodology to implement systemic safety management.) As a general rule, similar to crash data, reliable traffic volume data are more readily available for state-maintained roads, while reliable traffic volume data are less likely to be available for county and local roads. Thus, in most cases, appli cation of SPFs and the Safety Analyst and usRAP ViDA software will not be used to analyze and program systemic projects for county and local roads. Q. 2B. Does your agency have reliable traffic volume data for your entire roadway network or portions of the network? a. Response: Yes. If the answer is yes, then application of the FHWA Systemic Tool methodology and application of the usRAP methodology, using the associated ViDA software, are still both potential options for implementing systemic safety manage- ment, with further considerations to be made. (Go to Question 3B.)

58 Guide for Quantitative Approaches to Systemic Safety Analysis b. Response: No. If the answer is no, then the only alternative available is using the FHWA Systemic Tool methodology to implement systemic safety management. Application of the usRAP methodology, using the associated ViDA software, requires reliable traffic volume data for implementation. (Recommendation: Consider using the FHWA Systemic Tool methodology to implement systemic safety management.) Q. 3A. Will your agency consider developing an in-house tool to implement systemic safety or prefer to use existing software? In making decisions between developing an in-house tool to implement systemic safety or making use of existing software, several issues should be considered: • Initial application of the FHWA Systemic Tool methodology to implement systemic safety management involves the least amount of data and manpower. Therefore, this application of systemic safety can be implemented in a relatively short timeframe and with minimal cost. As more contributing factors are incorporated into the screening methodology, implementation costs will increase due to data collection needs, which will also extend the timeframe for implementation. • Use of the ViDA software is free; however, the software has specific data requirements. Fortunately, the input data can be coded from review of aerial photos and street-level photos using highway agency photologs or web-based tools such as Google Earth® or Bing Streetside®. On average, it takes about 30 minutes of labor per mile for a trained coder to prepare the input data for a roadway. Thus, implementation time and costs for data entry will be relative to the size of the network to be analyzed; however, after the initial costs for data entry, minimal costs should be incurred to implement the usRAP methodology using the ViDA software. • Use of the Safety Analyst software requires purchase of an annual license from AASHTO. For fiscal year 2020, the annual license fee for a site license was $37,200. Also, the software requires mapping and importing of data elements that can be quite burdensome to agencies with respect to implementation time and cost. The required data elements include inventory data for roadway segments, inter sections, and/or ramps; traffic volume data; and crash data. Most of the required data elements are FDEs as designated in MIRE, and states are required to have access to a complete collection of the MIRE FDEs on all public roads by September 30, 2026. • The implementation time and cost of developing an in-house tool to implement systemic safety will depend on the complexity and sophistication of the procedures and tool. a. Response: Existing software. If the answer is existing software, then application of SPFs using Safety Analyst software and application of the usRAP methodology, using the associated ViDA software, are still both potential options for implementing systemic safety management, with further considerations to be made. Application of the FHWA Systemic Tool methodology is no longer an option as no existing software is available that fully applies this methodology. (Go to Question 4A.) b. Response: In-house tool. If the answer is in-house tool, then application of the FHWA Systemic Tool methodology and application of SPFs are still both potential options for implementing systemic safety management, with further considerations to be made. However, application of the usRAP methodology, using the associated ViDA software and use of the Safety Analyst software are removed from further consideration by selecting in-house tool. It should be made clear that no existing software exists to fully implement the FHWA Systemic Tool methodology. It is up to an agency to develop internal procedures and tools to implement this systemic safety management approach. Application of SPFs for implementing systemic safety management, without the use of Safety Analyst, will require development of

Selecting the Appropriate Systemic Safety Management Approach and Software Tool 59 in-house tools such as spreadsheets or other customized tools to perform calcula- tions. (Go to Question 5A.) Q. 3B. Will your agency consider developing an in-house tool to implement systemic safety or prefer to use existing software? In making decisions between developing an in-house tool to implement systemic safety or making use of existing software, refer to the discussion points under Question 3A. a. Response: Existing software. If the answer is existing software, then your agency should consider using usRAP ViDA software to implement systemic safety man- agement. Use of the ViDA software is free, so once an agency has built the input database, applying the usRAP methodology and software is straightforward and inexpensive. The output results are also scientifically based and backed by research. (Recommendation: Consider using usRAP ViDA software to implement systemic safety management.) b. Response: In-house tool. If the answer is in-house tool, then the only remaining alternative is use of the FHWA Systemic Tool methodology to implement systemic safety management. Application of the usRAP methodology using the associated ViDA software is removed from further consideration by selecting in-house tool. It should be made clear that no existing software exists to fully implement the FHWA Systemic Tool methodology. It is up to an agency to develop internal procedures and tools to implement this systemic safety management approach. (Recommendation: Consider using the FHWA Systemic Tool methodology to implement systemic safety management.) Q. 4A. Do you want to make use of SPFs developed through regression analysis and use Empirical Bayes (EB) procedures while implementing systemic safety management procedures? a. Response: Yes. If the answer is yes, then application of SPFs using Safety Analyst software is the primary option for implementing systemic safety management. Use of SPFs and EB procedures for network screening and other steps in roadway safety management, as described in the HSM, have become accepted as a reliable best practice, but due to the data requirements and costs associated with Safety Analyst, further considerations need to be made. (Go to Question 6A.) b. Response: No. If the answer is no, then your agency should consider using usRAP ViDA software to implement systemic safety management. Use of the ViDA software is free, so once an agency has built the input database, applying the usRAP method- ology and ViDA software is straightforward and inexpensive. The output results are also scientifically based and backed by research. (Recommendation: Consider using usRAP ViDA software to implement systemic safety management.) Q. 5A. Does your agency have the resources or means to develop or calibrate planning- level SPFs? a. Response: Yes. If the answer is yes, then your agency should consider developing in-house tools to implement systemic safety management using SPFs. Some agencies may have the skill sets to develop SPFs for their roadway network, while other agencies may choose to hire universities or consultants to develop SPFs for their roadway network. Another alternative is to calibrate existing SPFs developed by others. Depending on the complexity of the tool, an agency may find it more cost effective to develop in-house tools to implement systemic safety management using SPFs, rather than using Safety Analyst, with the benefit of using accepted best prac- tices. (Recommendation: Consider developing in-house tools to implement systemic safety management using SPFs.) b. Response: No. If the answer is no, your agency is back to using the FHWA Systemic Tool methodology to implement systemic safety management. Without the resources

60 Guide for Quantitative Approaches to Systemic Safety Analysis or means to develop or calibrate planning-level SPFs, your agency cannot develop an in-house tool to apply SPFs for systemic safety. Again, it should be made clear that no existing software exists to fully implement the FHWA Systemic Tool method- ology. It is up to an agency to develop internal procedures and tools to implement this systemic safety management approach. Through this logic, it is possible that traffic volume and crash data could still be considered as contributing factors in the network screening methodology. (Recommendation: Consider using the FHWA Systemic Tool methodology to implement systemic safety management.) Q. 6A. Can your agency’s traffic volume, roadway inventory, and crash data be mapped into Safety Analyst? a. Response: Yes. If the answer is yes, then your agency should consider using Safety Analyst software to implement systemic safety management. To answer this question, an agency should first conduct a gap analysis to determine if its data are compatible for use within Safety Analyst. Safety Analyst uses common roadway inventory, traffic volume, and crash data to estimate network performance, but these datasets often exist in different offices and databases within an agency and sometimes are avail- able only from external agencies. These datasets must be mapped and integrated for use within Safety Analyst. There are certain data elements that are required for use within the software. Lack of a required data element will invalidate a site or crash or prevent it from being analyzed. Most of the required data elements are MIRE FDEs. States are required to have access to a complete collec tion of the MIRE FDEs on all public roads by September 30, 2026, but this is a work in progress. Agencies are still working to collect these MIRE FDEs and may not currently have all of the required data elements to make full use of the Safety Analyst functionality and capabilities. Fortunately, agencies can still use Safety Analyst if they do not have all of the required data elements. The purpose of the gap analysis is to determine what required data elements are readily available within existing datasets, assess the level of Safety Analyst functionality that can be accomplished in the short term, and assess the level of effort required to collect additional data elements in the long term to make further use of the Safety Analyst functionality and capabilities and/or to expand the network and site types that can be analyzed with the software in the future. Most state agencies initially develop their Safety Analyst dataset for their statewide network so they can analyze their state system, with the goal to incorporate and analyze data for local roads and intersections at a later date. (Recommendation: Consider using Safety Analyst software to implement systemic safety management.) b. Response: No. If the answer is no, returning to Question 3A is recommended. (Will your agency consider developing an in-house tool to implement systemic safety or prefer to use existing software?)

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Traditional approaches to safety have focused on identifying high-crash locations and implementing projects to address predominant concerns at these locations. The systemic approach to safety is a method of safety management that typically involves lower unit cost safety improvements that are widely implemented based on high risk factors.

The TRB National Cooperative Highway Research Program's NCHRP Research Report 955: Guide for Quantitative Approaches to Systemic Safety Analysis provides guidance to state departments of transportation (DOTs) and other transportation agencies on how to apply a systemic safety management approach for identifying safety improvement projects.

Material associated with the report includes NCHRP Web-Only Document 285: Developing a Guide for Quantitative Approaches to Systemic Safety Analysis and a PowerPoint of the summary of project findings and future research needs.

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