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                        Road Safety Audit Case Studies: Using IHSDM in the RSA Process


            
            In This Section
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                APPENDIX A: RSA CASE STUDY DETAILS: RSA No. 3 – US 97, Klamath County, Oregon
**Project Overview**Project Location:
			9.4 miles of US 97, from Modoc Point to Shady Pine Road in Klamath County, Oregon.Project Environment:
			RuralProject Design Stage:
			Conceptual (0-30%)Planned Improvements:
			Cold plane removal and overlay of the existing surface.
				Widening of shoulders to 8 feet along some sections.
				Elimination or protection of clear zone safety issues.
				New and upgraded barriers, guardrails, and end terminals.
				Minor realignment to improve sight distances and to move the highway away from some rock fall areas.
				Construction of retaining walls.Project Owner(s):
			Oregon Department of Transportation**RSA Overview**Date of RSA:
			April 11-13, 2006RSA Stage(s):
			Design StageRSA Team:
			Representatives from the Federal Highway Administration (including Office of Safety, Resource Center, and Oregon Field Office), Oregon Department of Transportation, Vanasse Hangen Brustlin, Inc., and Opus Hamilton Consultants.**IHSDM Overview**Information Provided by Roadway Owner:
			As-built roadway centerline.

			Proposed roadway alignment and improvement design.

			Traffic data

			Crash dataIHSDM Modules Utilized:
			Policy Review Module: Stopping Sight Distance

			Design Consistency Module

			Crash Prediction Module (using site-specific historical crash data).RSA No. 3 – Project Background

FHWA and the Oregon Department of Transportation (ODOT) partnered to conduct an RSA along US Highway 97 in south central Oregon, between Modoc Point and Algoma in Klamath County. In this area, the US 97 alignment passes along the east side of Upper Klamath Lake and the Union Pacific Railroad (see Figure 15). ODOT noted the presence of narrow shoulders, steep cut and fill slopes, and various fixed objects within the clear zone, including barriers, guardrail, and guardrail end terminals that did not meet current standards.

Figure 15: Aerial map of the US Highway 97 Study Corridor. US Highway 97 is highlighted in orange with Upper Klamath Lake to the left. A callout box with the beginning of the project is at mile point 257.8 and another callout box at the end of the project at mile point 267.2.

**Figure 15: US Highway 97 Study Corridor.**

Figure 16: Photo of a car travelling along a horizontal curve toward the viewer. A mile marker sign is bent and steep terrain is on the right hand side. Fallen rock lays along the side of the road.

**Figure 16: Rockfall in US 97 RSA Study Area.**

To address these and other concerns, a two-phase road improvement project was adopted by ODOT. The Phase One work began in early 2005 and was in progress at the time of the RSA; it included replacement/repair of four bridges, as well as rockfall work and widening on the east side of the highway. The Phase Two work, with a projected completion date of November 2009, would comprise improvements on the west side of US 97–between the highway and the adjacent railroad tracks. Constraints included topography and steep slopes, rockfall issues, the adjacent Union Pacific Railroad right-of-way and culturally sensitive sites of the area’s Native American tribes, and the need for the road to not only remain open to traffic during construction but also maintain certain minimum lane widths to accommodate heavy truck traffic.

RSA No. 3 – Use of IHSDM

The RSA team reviewed safety conditions on US 97 utilizing recent crash data, local and RSA team inputs, and IHSDM. IHSDM was used to help select sites for detailed review and to help identify priority areas where improvements should be considered. The project team utilized three IHSDM modules: the Policy Review Module (PRM), the Design Consistency Module (DCM), and the Crash Prediction Module (CPM).

The IHSDM analysis produced output tables and graphs that illustrate locations where stopping sight distance was not met, where the differential in speed from a tangent section to subsequent horizontal curve are a concern, and where crash potential is elevated. The results by module are summarized as follows:

**PRM:**The available stopping sight distance at two locations did not meet the minimum criteria set forth by the 2004 AASHTO "Green Book." In Figure 17 are the available sight in gold for the northbound direction and in blue for southbound). Note the circle on the graph indicates a location where a combination of critical elements identified by IHSDM are present. This location was one of the most critical based on PRM and DCM output.

Figure 17: Two line graphs show the Stopping Sight Distance Available verses Required. The top line graph shows the direction of decreasing stations in feet. The bottom line graph shows the direction of increasing stations in feet. A yellow line represents the required sight distance in decreasing stations. A green line depicts the available sight distance in decreasing stations. A blue line represents the required sight distance in increasing stations. A red line depicts the available sight distance in increasing stations. A yellow circle calls out a point where the red line and the blue line cross at a short interval.

**Figure 17: A Section of US 97 IHSDM PRM Stopping Sight Distance Graph.**

Figure 18: Photo of two vehicles travelling along a horizontal curve in rainy and cloudy conditions. The road is wet with guardrails and concrete barriers on each side. Fog and clouds reduce visibility.

**Figure 18: Sight distance is limited on horizontal curves with barriers.**

**DCM:**The output from this module showed that the expected reduction in estimated 85th percentile speeds from an approach tangent to its succeeding horizontal curve were all flagged as "green," indicating the speed differential is less than 6 mph (in Figure 19, see 85th percentile speed plotted for the northbound direction with green flags indicating speed differential). Two horizontal curve locations that approached this threshold were noted, but overall design consistency was fairly uniform. Note the circle on the graph indicates a location where a combination of critical elements identified by IHSDM are present. This location was one of the most critical locations based on PRM and DCM output.

Figure 19: Image showing the summary of US Highway 97 IHSDM DCM output. A line graph depicts the direction of travel with different color lines representing the Intersection, Elevation (ft), KValue (ft/%), Radius (ft), Degree of Curve (dcg), and speed (mph).

**Figure 19: Summary of US 97 IHSDM DCM Results.**

**CPM** – Five years of historical crash data–including 74 reported collisions from January 1, 2000 to December 31, 2004– were considered by the CPM analysis for the section of the alignment from milepost 262 to milepost 267.2. The expected crash rate (crashes/mi/yr) for each homogeneous roadway segment and horizontal design element was graphed as part of the default IHSDM output (see Figure 20). The results indicated that expected crash rates are higher at horizontal curves with short radii.

Figure 20: Image showing the summary of US Highway 97 IHSDM CPM results on segment evaluated as part of RSA. A line graph contains different color lines representing the elevation, radius, crash rate by segment, and crash rate by horizontal design element.

**Figure****20: Summary of US 97 IHSDM CPM Results on Segment Evaluated as Part of RSA.**

RSA No. 3 – Key RSA Findings and Suggestions

A summary of the key RSA findings and suggestions is shown in Table 7.

**Table 7: US 97, Klamath County, Oregon: Key safety issues and suggested mitigating actions.**

Selected Safety Issue
			Suggested Action**Roadside safety issues**
			There were steep slopes and ditches within the clear zone, unprotected utility poles, and shoulder edge-drops.
			Additional roadside barriers.

			Relocation or shielding of utility poles.

			Use Safety Edge to limit edge-drops.**Sight distance**
			Sight distance was constrained by roadside topography, rockfall fences, and bridge superstructures at horizontal curves and at intersections.
			Confirm stopping sight distance.

			Review of specified sight distance obstructions at intersections and improve as needed.**Limited night-time guidance**
			There was limited night-time guidance provided on this curved alignment with steep side slopes. An enhanced level of delineation would be beneficial along this hazardous segment of roadway.
			Enhanced post-mounted delineators.

			Improved centerline and edgeline delineation.**Signage**
			Signing issues included possible re-use of faded signs, missing intersection warning signs, and use of small lettering on street name signs.
			Intersection warning signs.

			Advance street name signs and larger street name signs.

			Confirm retroreflectivity of reused signs and replace as necessary.**Rockfall protection**
			Rockfall protection formed an important part of the design requirements. The very challenging improvement site may be a candidate for the use of enhanced rockfall protection measures.
			Enhanced rockfall protection measures if standard measures are ineffective, infeasible, or create other undesirable conditions.**High speeds**
			High speeds contributed to increased collision risk and severity.
			Use IHSDM speed profiling in speed enforcement efforts.

			Variable speed limits.**Winter weather**
			A high proportion of crashes occurred under winter road conditions.
			Ice detection and warning system.RSA No. 3 – Conclusions

IHSDM provided key inputs to the RSA team based on several modules that helped it to identify potential safety issues along the corridor. The use of IHSDM allowed a comparison between the existing available stopping sight distance and the stopping sight distance associated with the proposed design. It also predicted crashes along the future roadway based on its geometric characteristics and projected traffic volumes. IHSDM highlighted locations where drivers may need to decelerate to safely negotiate a horizontal curve, thereby assisting in the prioritization of locations for review by the RSA team.

The ability to quantify values associated with design issues (e.g., stopping sight distance) and to estimate future crash frequencies based on the road redesign enhanced the value of the RSA by demonstrating the magnitude of the safety issues identified by the RSA team. Without IHSDM estimates, the RSA team could identify–but could not necessarily quantify–expected changes in safety parameters such as operating speeds or expected crash frequencies. Quantifying these parameters and frequencies provided a higher level of confidence to all parties (the RSA team, Design Team, and Owner) concerning the magnitude and importance of the safety issues identified in the RSA.

Furthermore, opportunities for using IHSDM output beyond engineering were identified. Law enforcement indicated an interest in reviewing locations where speed may be a concern as identified by the DCM.
      
  Book traversal links for APPENDIX A: RSA CASE STUDY DETAILS: RSA No. 3 – US 97, Klamath County, Oregon
      ‹ APPENDIX A: RSA CASE STUDY DETAILS: RSA No. 2 – US Highway 2, Kalispell, Montana
                    Up
                    APPENDIX B: IHSDM DATA REQUIREMENTS AND ANAYSIS METHODOLOGY ›
                
                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

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