Highway Safety Manual Frequently Asked Questions
1. General Information
2. HSM-related Tools
3. Specific Technical Issues
1. General Information
What Is the Highway Safety Manual, and Why Was It Developed?
The Highway Safety Manual (HSM) provides 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. Prior to the HSM, there was no widely accepted tool available to quantitatively assess the impact of infrastructure decisions on safety.
Is the HSM Required?
Each state department of transportation can set its own policy related to use of the manual, if desired. The Federal Highway Administration does not require use of the Highway Safety Manual. The HSM is a tool to help practitioners perform data-driven safety analyses of roads, and is not a standard or a requirement.
How Is the Highway Safety Manual Related to the AASHTO Green Book and Roadside Design Guide?
The Highway Safety Manual provides information and tools for incorporating data-driven consideration of safety into the project planning and development process. The manual allows for determining the impacts of design and other decisions on the expected safety performance of a facility. The AASHTO Policy on Geometric Design of Highways and Streets (the “Green Book”) and Roadside Design Guide are publications that present current information on design and operating practices that are in universal use in the United States. Where these publications present recommended ranges of values for given elements in the roadway or roadside environment, the HSM allows for determining the expected safety impact of using a specific value over another value.
Where Can I Find an Overview of the HSM?
The Highway Safety Manual website, www.highwaysafetymanual.org, has an Introduction or “primer” on the HSM, as well as a fact sheet and brochure.
Recordings of the FHWA HSM webinar series are available on the HSM website also, on the Training page. The first webinar in the series is an overview.
Where Can I Find Information on Training?
The Training page of the HSM website has information on HSM courses currently available and under development. The National Highway Institute of FHWA has several courses related to the HSM. State departments of transportation can contact their FHWA Division Office for training assistance.
Can I Download the FHWA Webinar Recordings?
The recordings of the FHWA webinar series are posted on the HSM website. If you’re unable to view these recordings online, send a message to email@example.com for assistance.
Where Can I Find Other HSM Users?
There is an online user discussion forum that provides a place for HSM users to ask questions to other practitioners or to provide information on their experiences. This forum is monitored to ensure questions are answered if no other users are able to respond. You can view posts to this forum and responses without being a member. Additional information is on the User Discussion Forum page on the HSM website.
The Transportation Research Board Highway Safety Performance Committee deals with quantitative highway safety information to support inclusion of safety in decisions at all points in the project development process. This committee has a website for HSM research and other information it develops and promotes. The committee meets during the annual TRB meeting in January and also holds a mid-year meeting; these meetings are open to all.
Where can I get help with the manual?
You can send questions on the manual to firstname.lastname@example.org or you can post questions on the User Discussion Forum. Questions from both sources are passed along to technical experts for answers if needed. You can also browse the discussion forum to see if a similar question has been posted. As new technical resources are developed, they will be posted on the HSM website on the Technical Support page.
Where do I find /send potential errata?
All Errata are posted on the HSM website. Please submit information on potential errors in the HSM to email@example.com, or post the information on the User Discussion Forum.
How do I suggest additions to the HSM?
If you have suggestions on material to add to the HSM, please send a message to firstname.lastname@example.org, or post your suggestions on the User Discussion Forum.
When will the next edition of the manual be published?
It will several years until publication of the second full edition of the HSM. The AASHTO Subcommittee on Safety Management Task Group on Technical Publications and the TRB Highway Safety Performance Committee have worked together closely on a workplan for the second edition, developed under an NCHRP project. This work plan helps to prioritize research needed for future editions.
NCHRP Project 17-45, Enhanced Safety Prediction Methodology and Analysis Tool for Freeways and Interchanges, will develop predictive models for freeways and interchanges similar to those found in Part C of the HSM for other facility types. AASHTO expects to publish this new chapter of the HSM when it is available, rather than waiting to include it in the next full edition. A project to develop predictive models for six-lane urban and suburban arterials and one-way arterials has been approved for the fiscal year 2012 NCHRP program (project 17-58).
FHWA’s Crash Modification Factor Clearinghouse will post periodically new CMFs – new research is reviewed quarterly to identify CMFs for posting. You can also submit CMFs to be added to the database on the Clearinghouse website at www.cmfclearinghouse.org. The Clearinghouse contains information on the relationship of the CMFs on the website to those published in the HSM.
Can a State Department of Transportation Use Federal Highway Safety Improvement Program Funds to Purchase The HSM?
FHWA has provided this information related to use of HSIP funds for the HSM:
Since the publication of the Highway Safety Manual (HSM), the FHWA Office of Safety has received a few inquiries concerning the eligibility of Highway Safety Improvement Program (HSIP) funds to support HSM implementation activities. Questions such as this are handled on a case by case basis. While the law (23 U.S.C. 148) and regulation (23 CFR 924) governing the HSIP lists transportation safety planning and improvement in the collection and analysis of safety data as eligible highway safety improvement projects, these activities must directly support HSIP implementation efforts.
States may also leverage other federal-aid funds to support HSM implementation efforts. For example, state planning and research funds can be used to support data collection efforts. In addition, training is an eligible expense under core federal-aid programs. Improvements to the collection and analysis of safety data can also be funded by NHTSA Section 402 and 408 State Highway Safety Grant Programs. CFR Title 49 Part 350 Commercial Motor Carrier Safety Assistance Program also has limited applicability for commercial motor vehicle involved crashes.
Several States have used HSIP funds for HSM implementation and related projects. However, every situation is unique and you should direct questions regarding HSIP eligibility to your state’s FHWA Division Office or Karen Yunk in the FHWA Office of Safety at 609-637-4207 or email@example.com.
3. HSM-related Tools
This section provides an overview of the relationship of several tools to the Highway Safety Manual.
SafetyAnalyst provides a set of software tools used by state and local highway agencies for highway safety management. It incorporates state-of-the-art safety management approaches into computerized analytical tools for guiding the decision-making process to identify safety improvement needs and develop a systemwide program of site-specific improvement projects. SafetyAnalyst is applicable to Part B of the HSM. The SafetyAnalyst software is available through AASHTO, and additional information can be found at www.safetyanalyst.org.
Interactive Highway Safety Design Model
The Interactive Highway Safety Design Model (IHSDM) is a suite of software analysis tools for evaluating safety and operational effects of geometric design decisions on highways. It checks existing or proposed highway designs against relevant design policy values and provides estimates of a design’s expected safety and operational performance. The IHSDM performs the predictive method for the facilities in Part C of the first edition of the HSM (i.e., two-lane, two-way rural roads, rural multilane highways, and urban and suburban arterials). The IHSDM website summarizes the capabilities and applications of the evaluation modules and provides a library of the research reports documenting their development. Information is available at the public software website, www.ihsdm.org, where users can register and download the latest release of IHSDM.
Crash Modification Factor Clearinghouse
The Crash Modification Factors Clearinghouse houses a web-based database of CMFs along with supporting documentation to help transportation engineers identify the most appropriate countermeasure for their safety needs. Using this site at www.cmfclearinghouse.org, users are able to search for existing CMFs or submit their own CMFs to be included in the clearinghouse.
Does PLANSAFE Implement the Highway Safety Manual?
A software tool was developed to complement NCHRP Report 546, Incorporating Safety into Long Range Transportation Planning. PLANSAFE is a software tool that supports regional and statewide safety planning efforts. It does not implement portions of the Highway Safety Manual or overlap with the functionality of IHSDM or SafetyAnalyst. While PLANSAFE could be used for analysis of changes in individual locations, the level of detail needed to make decisions at this level is not supported by PLANSAFE, as the documentation for the tool cautions. For more information, refer to NCHRP Report 546 or the web page for NCHRP Project 8-44(02), under which PLANSAFE was developed.
3. Specific Technical Issues
How should default values in the HSM be handled?
The HSM provides default values for items such as costs of injuries, severity distributions, and percentage of animal crashes. These defaults are the most appropriate values for inclusion in a manual to be used by a variety of agencies and organizations across the country, but if a user has reliable local values, the local values should be used instead of defaults. This will provide results more applicable to the specific situation for which the HSM is being used.
Does the HSM Cover…?
1. Guidelines for crash testing safety hardware?
No. Resources for this include the Manual for Assessing Safety Hardware and the earlier NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features.
2. One-way streets?
The HSM briefly discusses the expected impact of removing an unwarranted signal on a one-way street (Part D, Chapter 14) and converting one-way streets to two-way (Part D, Chapter 17). One-way arterials will be included in upcoming research sponsored by the National Cooperative Highway Research Program (project 17-58).
3. Pedestrians? Bikes?
HSM information on non-motorized road users is spread throughout the manual. Chapter 13, on crash modification factors for roadway segments, contains information on the expected impact of treatments related to pedestrians and bicyclists. There is not enough information available to develop crash modifications factors, but this chapter does contain information on trends. Chapter 12 includes a pedestrian crash prediction method for signalized intersections, including SPFs and CMFs; pedestrian crash adjustment factors for stop-controlled intersections and segments; and bicycle crash adjustment factors for segments and intersections.
While expected impacts of treatments related to on-street parking are discussed in the HSM (Part D, Chapter 13), many issues related to parking have not undergone the type of study necessary for inclusion in the HSM. An on-street parking CMF is part of the crash prediction method for urban/suburban arterials in Chapter 12.
5. Animal crashes?
The HSM provides default percentages of animal crashes for use in Part C predictive models. For rural two-lane roads, this information is in Chapter 10. Chapter 12 contains the information for urban and suburban arterials. For rural multi-lane roads (Chapter 11), this information is not available. If percentages of animal crashes are available for a state or region for which an analysis is being performed, these values can be used instead of those provided by the HSM.
6. At-grade rail crossings?
The HSM will provide some information on crash effects of treatments related to highway-rail grade crossing traffic control and operational elements (Part D, Chapter 16). There are crash modification factors for signs and markings, signals and gate (active and passive), and illumination. There are a few other treatments for which trends are discussed, but for which enough information was not available to provide a CMF. These treatments are strobes, four-quadrant gates, pre-signals, and constant warning time devices.