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FHWA Home / Safety / HSIP / HRRR / Manual for Selecting Safety Improvements on High Risk Rural Roads

3. Identifying Safety Treatments

This chapter discusses several tools that can be used to identify and select safety treatments and presents the differences between the traditional methods of treating "spot" locations versus a systemic approach.

3.1. Tools for Identifying HRRR Safety Issues

Technical expertise is cited as one of the most significant obstacles facing agencies when attempting to identify and implement safety treatments. Fortunately, many safety tools and opportunities for training exist for State and local transportation agencies. This section describes safety tools to assist with safety needs identification, use of available data—however limited—to make informed decisions with respect to selecting treatments, and additional resources and training opportunities.

Highway Safety Manual

The Highway Safety Manual (HSM) "Frequently Asked Questions" page describes the manual as providing:

"... practitioners with information and tools to consider safety when making decisions related to design and operation of roadways. The HSM assists practitioners in selecting countermeasures and prioritizing projects, comparing alternatives, and quantifying and predicting the safety performance of roadway elements considered in planning, design, construction, maintenance, and operation."8

The HSM uses data to estimate the safety impacts of incorporating safety features for existing roads or future projects by determining the impacts of design and other decisions on the expected safety performance of a facility.

Safety Analyst

The Safety Analyst tool assists in making site-specific safety improvement recommendations that involve physical modifications to the roadway, either through systemic or spot location applications. As spot locations are being examined, the tool can help to identify crash patterns at specific locations and determine whether those crash types are overrepresented and the frequency at which crashes occur. The tool can help to identify opportunities for systemic solutions by identifying overrepresented crashes and clusters for highway segments or intersection types.9

Safety Analyst has the following capabilities to aid practitioners in each step of the safety management process, from needs identification to implementation and evaluation:

Crash Modification Factor (CMF) Clearinghouse

The CMF Clearinghouse website10 provides a collection of calculated crash modification factors practitioners can apply to estimate the benefits of specific safety treatments. The website can be used by searching for a particular treatment name, which can be further refined by crash type or severity, roadway or intersection type, area type (e.g., urban, suburban, rural), and intersection geometry. Each safety improvement in the clearinghouse shows a CMF and Crash Reduction Factor (CRF), in addition to the quality or rating of the CMF. The quality rating indicates the quality or confidence in the results of the study producing the CMF.11 CMFs and CRFs are accompanied with details of the research conducted to develop the CMF.

Road Safety Audits

A Road Safety Audit (RSA) is the formal safety performance examination of an existing or future road or intersection by an independent, multidisciplinary team. It qualitatively estimates and reports on potential road safety issues and identifies opportunities for improvements in safety for all road users.12 RSAs can be integrated into the project development process for new roads and intersections, on existing roads and intersections, and for future or existing work zones.

For HRRR, the multidisciplinary team's expertise can include those familiar with rural issues, law enforcement officers, emergency service providers, human factors experts, and engineering fields including design, traffic safety, operations and maintenance, and others. The team assesses site-specific conditions and recommends improvements based on the team's road safety expertise in each member's respective fields.

RSAs can help to reduce crash severity and frequency while accounting for all road users. If performed during the design phase, RSAs serve as a proactive approach to improving safety before construction begins.


Opportunities for and depth of training vary based on the agency's need. Practitioners can inquire about training based on their own specific needs beginning with the following resources:

3.2. Systemic Implementation and Spot Location Treatments

A challenge in addressing safety in rural areas is that crashes tend to be widely dispersed geographically. The high number of lane miles and the dispersed nature of crashes make it difficult to target specific locations for assessment and improvement. Therefore, applying a systemic approach to addressing safety issues is a beneficial method for proactively addressing widespread safety concerns and cost-effectively minimizing crash potential. Rather than focus on specific crash locations, a systemic approach targets common risk factors in crashes throughout the roadway network. A systemic improvement is widely implemented based on high-risk roadway features that are correlated with particular crash types rather than location-based crash frequency. The systemic problem identification entails a system-wide crash analysis targeting specific crash characteristics at the system level.

Systemic solutions can reduce overall severe crashes of certain types in a jurisdiction more effectively than choosing a small number of spot locations. This approach allows an agency to compensate for incomplete and lower quality crash history or roadway data, as it is less vital for that information to be perfect when many locations or segments are addressed with low-cost treatments.

With the systemic approach, implementation must be widespread enough to make a region-wide impact. Additionally, it can sometimes be difficult to convince stakeholders to apply safety treatments (even if low-cost) at locations that do not have a history of crashes.

Traditionally, a common approach has been to identify "black spots," or locations with the highest crash frequency. While specific implementation sites are easily identified using roadway and crash data, this approach does not adequately deal with the randomness of the location of fatal and severe injury crashes. The traditional approach does not directly account for the most prevalent risk types associated with system-wide crashes.

This manual presents safety treatments that can be applied systemically, specifically at spot locations, or using both implementation methods.

For additional information on spot location and systemic safety treatment installations, please visit the following resources:

8 AASHTO, "Highway Safety Manual-Related Frequently Asked Questions (FAQs)," last modified June 14, 2013, http://www.highwaysafetymanual.org/support.aspx. [ Return to note 8. ]

9 Safety Analyst website, accessed October 9, 2013. http://www.safetyanalyst.org/. [ Return to note 9. ]

10 CMF Clearinghouse website, accessed October 9, 2013. http://www.cmfclearinghouse.org. [ Return to note 10. ]

11 CMF Clearinghouse website, "About the Star Quality Rating," accessed October 9, 2013. http://www.cmfclearinghouse.org/sqr.cfm. [ Return to note 11. ]

12 FHWA Road Safety Audit website. Accessed October 9, 2013. http://safety.fhwa.dot.gov/rsa/. [ Return to note 12. ]

13 Local and Tribal Technical Assistance Program website, accessed December 3, 2013. http://www.ltap.org/. [ Return to note 13. ]

14 Highway Safety Manual Training website, accessed December 3, 2013. http://www.highwaysafetymanual.org/Pages/Training.aspx. [ Return to note 14. ]

15 National Highway Institute website, accessed December 3, 2013. https://www.nhi.fhwa.dot.gov/default.aspx. [ Return to note 15. ]

16 FHWA Road Safety Audit website, accessed December 3, 2013. http://safety.fhwa.dot.gov/rsa. [ Return to note 16. ]

17 National Association of County Engineers website, accessed December 3, 2013. http://www.countyengineers.org. [ Return to note 17. ]

18 National Association of Counties website, accessed December 3, 2013. http://www.naco.org.[ Return to note 18. ]

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