USA Banner
  U.S. flag
              An official website of the United States government Here's how you knowOfficial US Government Icon
              **Official websites use .gov**A **.gov** website belongs to an official government organization in the United States.
            Secure Site Icon
              **Secure .gov websites use HTTPS**
                  A **lock** ( A locked padlock ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites. 
 U.S. Department of Transportation Icon United States Department of Transportation
 Search DOT
            Search
                    About FHWAFHWA Organization
                Headquarters Offices
                Field Offices
                Strategic Plan
                Business Opportunities
                Staff Directories
                Careers
                Highway History
                Contact UsProgramsAcquisition Management
                Civil Rights
                Federal Lands Highway
                Infrastructure
                Innovative Program Delivery
                Operations
                Planning, Environment, and Realty
                Policy
                Research, Development, and Technology
                Safety
                Browse by TopicsResourcesCore Highway Topics
                Federal Aid Essentials
                Automation
                Complete Streets
                Laws and Regulations
                Policy & Guidance Center
                Section 508
                Publications and Statistics
                Professional Development
                National Highway Institute
                Resource Center
                Accessibility Resource Library
                FHWA Research LibraryNewsroomPress Releases
                Speeches & Testimony
                Photos
                Videos
                Media ContactsMenu FHWA Highway Safety Programs Home
                        Road Safety Audit Case Studies: Using IHSDM in the RSA Process


            
            In This Section
        Safety Data Analysis & Tools
                Crash Modification Factor Clearinghouse
                Roadway Safety Data Program (RSDP)
                                Overview
                Data Driven Safety Analysis
                Data Management
                Safety Data Analysis Tools
                Local Data Integration
                Technical Assistance
                Case Studies
                Training
                Resources
                Highway Safety Manual (HSM)
                Model Inventory of Roadway Elements (MIRE) and FDEs
                Systemic
                                Overview
                Why Systemic
                Training
                Resources
                Road Safety Audits
                                Overview
                Benefits
                Legal Issues
                Steps of Conduct
                Training
                Resources
                
                Using IHSDM in the RSA Process
RSA Projects Selected

This effort was comprised of three RSAs in different regions of the country, as shown in Table 2, which incorporated utilizing IHSDM in the standard eight-step RSA process. These sites were selected based on the following criteria:

A demonstrated need for an RSA
	Availability of design data to input into IHSDM
	Variation in geographic locationA more detailed report of these three RSAs is included in Appendix A.

**Table 2: RSAs Conducted Using IHSDM.**

**Location and Host Agencies**
			**Facility Type and Project Stage**
			**Length of Segment Studied**Snake Hill Road in Glocester, Rhode Island; Rhode Island Department of Transportation (RIDOT)
			Existing two-lane rural highway.
			7.4 milesUS Highway 2 in Kalispell, Montana; Montana Department of Transportation (MDT)
			Existing two-lane rural highway.
			26.1 milesUS 97, Klamath County, Oregon; Oregon Department of Transportation (ODOT)
			Existing two-lane rural highway and proposed roadway improvements.
			9.4 milesOverview of How IHSDM was used in the RSA Process

IHSDM output was reviewed by the RSA team during the start-up meeting (Step 3 in the RSA process) and during the RSA analysis workshop (Step 5 in the RSA process). During the start-up meeting one person familiar with using IHSDM described and interpreted key program results including the location of potentially critical conditions and the potential effect on crashes. These were then reviewed in detail in the field (Step 4 in the RSA process). Later, during the RSA analysis workshop, a more detailed review of the IHSDM output was conducted. The objective of this review was to more thoroughly discuss the analysis results and to compare these results with conditions observed in the field.

Data Requirements

In order to analyze a roadway using IHSDM, geometric, roadside, crash, and traffic data are needed to analyze and identify conditions along the corridor. These data requirements vary for each module but the basic geometric elements required are the roadway horizontal alignment, vertical alignment, and cross-sectional data (roadway cross-section and roadside). Horizontal alignment data is represented by a series of tangent (i.e., straight) sections and horizontal curves defined by project stations. Vertical alignment data is categorized as Level I or Level II, with Level I being the complete vertical alignment data to include grades and vertical curves defined by project stationing and Level II being only vertical tangent data and no vertical curve data. However, IHSDM provides a methodology for estimating vertical curve elements with only the Level II data. The methodology is documented in the IHSDM Help Browser. Cross-sectional data includes road elements such as cross slope and superelevation and roadside elements such as obstruction offset, and roadside hazard rating. Roadway geometry data can be extracted from road design software by exporting to LandXML format and then importing into IHSDM; or may be entered manually into IHSDM via a Highway Editor graphic user interface (GUI). Roadside elements can also be translated from design software into LandXML but are usually entered manually into IHSDM via the Highway Editor due to difficulties or limitations on extraction from design software. Other data not stored in road design software such as traffic volume are also typically entered manually.

Figure 3: A screenshot from the IHSDM Highway Editor is shown for entering horizontal alignment data. Users can enter information such as the tangent or curve start and end stationing. For curves, the radius, direction, radius position, and deflection angle can also be entered.

**Figure 3: The IHSDM Highway Editor for entering horizontal alignment data.**

In general, geometric and other data are required for both roadways and intersecting streets in order to analyze intersections using IHSDM via the IRM. Since geometric data were only available for the mainline on the corridors selected for this project the IRM was not utilized for this project. The TAM and DVM were also not used due to lack of critical data elements specific to these modules. A detailed description of the data requirements and analysis methodology for the modules used is included in Appendix B.

Assembling and Entering Data

The following summarizes the approach used in each of the three RSAs to assemble and input data into IHSDM.

Rhode Island

The RSA Team utilized the following three IHSDM modules for the Snake Hill Road corridor:

Policy Review Module (PRM).
	Design Consistency Module (DCM).
	Crash Prediction Module (CPM).The only geometric data available for the Snake Hill Road corridor was in the form of as-built construction plans from the 1980s. In order to use the latest geometric data and streamline all the data input process into IHSDM, the RSA team used the following process, which used a combination of aerials, GIS, as-built plans, and field visits:

Import Google Earth aerial photo into AutoCAD (road design software).
	Create roadway centerline by tracing aerial image.
	Establish user-defined project stationing.
	Import vertical data from Rhode Island GIS (RIGIS with 5-foot interval contours).
	Fine tune vertical and horizontal alignment data from as-built plans, resulting in horizontal and vertical curve design based on user-defined project stationing.
	Import geometric data directly into IHSDM via the LandXML import tool.
	Manually enter cross sectional data from as-built plans via IHSDM Highway Editor.
	Reference crash location to user-defined project stationing.
	Manually enter crash location, crash type, and severity into IHSDM via the Highway Editor.
	Enter the remaining roadway characteristic data into IHSDM via the Highway Editor. Key elements include:
	Roadside Hazard Rating (a rating of the safety of the roadside as determined from field review/Google Earth Street View).
		Speed data (determined through review of posted speeds, which is used in the DCM, and collecting speed data along corridor).
		Average Annual Daily Traffic (AADT) volume data from RIDOT
		Obstruction offset (the distance from the centerline of the highway to sight obstructions as determined by estimating offset from Google Earth streetview and used to check stopping sight distance and passing sight distance in the PRM).Figure 4: A Google Earth aerial from Snake Hill Road RSA shows project stationing numbers and markings overlaid in white.

**Figure 4: Snake Hill Road RSA: Google Earth aerial with project stationing.**

Montana

The RSA Team utilized the following three IHSDM modules for the US Highway 2 corridor:

Policy Review Module (PRM).
	Design Consistency Module (DCM).
	Crash Prediction Module (CPM).Figure 5: A photo showing a winding road with a steep hill in the distance with trees along both sides of the road.

**Figure 5: US Highway 2 near MP 106 in Kalispell, Montana. IHSDM was used to identify this section as having an elevated crash potential as well as a location where the speed differential between straight and curve sections of the roadway may be a concern.**

As-built drawings with horizontal roadway geometry and excel spreadsheets with elevation data were provided by MDT for the section of the US Highway 2 corridor analyzed using IHSDM. The horizontal roadway geometry data was manually entered via the Highway Editor.

Since MDT provided elevation data for the roadway by milepost (MP) in an electronic spreadsheet format, the MPs were converted to project stations (accounting for station equations), then the elevation data were plotted to scale by the project team resulting in a roadway elevation profile. The team drew in the grades and connected these using vertical curves resulting in Level I vertical alignment data. The vertical alignment data was then entered into IHSDM manually via the IHSDM vertical data entry the Highway Editor. Other data was then gathered and entered into IHSDM similar to the Rhode Island Case Study.

Oregon

The RSA team utilized the following three modules for the US 97 corridor:

Policy Review Module (PRM).
	Design Consistency Module (DCM).
	Crash Prediction Module (CPM).The existing and proposed alignment for US 97 was provided to the RSA team in MicroStation format. Some data was able to be directly imported into IHSDM utilizing GEOPAK road design software; however, many elements were not able to be converted and much of the geometric data for the existing road was entered manually into IHSDM via the Highway Editor. More of the design elements from the proposed roadway were able to be converted directly into IHSDM data format. All roadside elements were entered manually.
      
  Book traversal links for Using IHSDM in the RSA Process
      ‹ IHSDM Overview
                    Up
                    Utilizing IHSDM Results ›
                
                Book:Road Safety Audit Case Studies: Using IHSDM in the RSA Process
              Executive Summary
                Background
                Eight Steps of an RSA
                RSAs: Benefits and Costs
                Purpose
                IHSDM Overview
                Using IHSDM in the RSA Process
                Utilizing IHSDM Results
                Conclusions and Recommendations
                References
                APPENDIX A: RSA CASE STUDY DETAILS: RSA No. 1 – Snake Hill Road, Glocester, Rhode Island
                APPENDIX A: RSA CASE STUDY DETAILS: RSA No. 2 – US Highway 2, Kalispell, Montana
                APPENDIX A: RSA CASE STUDY DETAILS: RSA No. 3 – US 97, Klamath County, Oregon
                APPENDIX B: IHSDM DATA REQUIREMENTS AND ANAYSIS METHODOLOGY U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

1200 NEW JERSEY AVENUE, SE

WASHINGTON, DC 20590

202-366-4000Subscribe to email updates
                    About
  

        
              About FHWA
                Careers
                Org Chart
                Staff Directories
                Work with UsPrograms
  

        
              Acquisition Management
                Civil Rights
                Federal Lands Highway
                Infrastructure
                Innovative Program Delivery
                Operations
                Planning, Environment, and Realty
                Policy
                Research, Development, and Technology
                SafetyPolicies, Rights, Legal
  

        
              About DOT
                Accessibility
                Budget and Performance
                Civil Rights
                FOIA
                Information Quality
                No FEAR Act
                Office of Inspector General
                Privacy Policy
                USA.gov
                Web Policies and Notices
                Web StandardsNews & Events
  

        
              Newsroom
                Press Releases
                Speeches & Testimony
                Media Contacts
                Connect with Us