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Road Safety Audits (RSA)
APPENDIX A
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| Project: improvements to two-lane rural highway in a constrained area | |||
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| Planned Improvements: |
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| Project Environment: | urban | suburban | x rural |
| Project Design Stage: | x conceptual (0 to 30%) | preliminary (40 to 80%) | advanced (over 80%) |
| Project Cost: | < $100,000 | $100,000 - $1,000,000 | x >$1,000,000 |
| Project Owner: | Oregan Department of Transportation | ||
| Road Safety Audit | |||
| Date of RSA: | 11-13 April 2006 | ||
| RSA Stage(s): | x design stage | RSA of existing roads | |
| RSA team: | staff from Federal Highway Administration (including Office of Safety, Resource Center, and Oregon Field Office), Oregon DOT, VHB, and Opus Hamilton Consultants | ||
PROJECT BACKGROUND:
FIGURE A.4 RSA SEGMENT OF US 97
The project, along US Highway 97 between Modoc Point and Algoma, was located in Klamath County in South Central Oregon. In this area, the US 97 alignment passes along the east side of Upper Klamath Lake and the Union Pacific Railroad (FIGURE A.4). The Oregon Department of Transportation (ODOT) identified several safety issues along this section of US 97, including a fatality rate of 5.3 per million vehicle miles, almost double the average rate for similar Oregon highways. The DOT noted the presence of narrow substandard shoulders widths, substandard cut and fill slopes, and unprotected safety issues within clear the zone, including barriers, guardrail, and guardrail end terminals that did not meet current standards.
To address these and other concerns, a two-phase road improvement program was adopted by ODOT. Phase One work, which began in early 2005 and was in progress at the time of the RSA, included replacement/repair of four bridges as well as rockfall work and widening on the east side of the highway. Phase Two work, which was to be let in September 2007 with a projected completion date of November 2009, was expected to take place on the west side of US 97, between the highway and the adjacent railroad tracks.
The improvement projects were subject to several conditions that imposed unique and substantial constraints on design and construction:
- Topography and slope stability were challenging constraints. Steep, unstable slopes were present on both sides of the highway (FIGURE A.4). The project limits included six rockfall sites, one of which would be affected by construction.
- To the west of the roadway, the Union Pacific Railroad imposed right-of-way constraints that affected road design. In addition, the railroad’s rockfall warning system affected construction methods.
- Cultural sites associated with the area’s Indian tribes affected slope stabilization efforts.
- The roadway, which was to remain open during construction, must accommodate mobility needs. ODOT required that the construction design maintain specified minimum lane widths and that average traffic delay not exceed six minutes. In addition, US 97 is a designated truck corridor, and was expected to accommodate additional truck traffic diverted from nearby construction works on Interstate Highway 5.
This RSA incorporated the use of the Interactive Highway Safety Design Model (IHSDM), a suite of software analysis tools3 being developed by the FHWA to provide an explicit, quantitative evaluation of safety and operational effects of geometric design on two-lane rural highways. IHSDM was used to evaluate the elements of the existing and proposed design against design policy values, design consistency, and to predict the expected safety of the future road. IHSDM may be downloaded free of charge at http://www.ihsdm.org.
KEY RSA FINDINGS AND SUGGESTIONS:
The key findings and suggestions of the RSA are summarized in TABLE A.3.
| SAFETY ISSUE (Number and Description) |
Risk Rating | Suggestions | |
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| 1 | Roadside safety issues included:
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D |
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| 2 | Sight distance was constrained by roadside topography, rockfall fences, and bridge superstructures at horizontal curves and at intersections. | C |
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| 3 | Limited night-time guidance was provided on a curved alignment with hazardous side slopes. An enhanced level of delineation would be beneficial along this hazardous segment of roadway. | B |
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| 4 | Signing issues included possible re-use of faded signs, missing intersection warning signs, and use of small lettering on street name signs. | B |
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| 5 | 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. | B |
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| 6 | High speeds contributed to increased collision risk and severity. | C |
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| 7 | Winter weather: A high proportion of crashes occurred under winter road conditions. | C |
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KEY LESSONS LEARNED:
The Interactive Highway Safety Design Model (IHSDM)is a useful tool toquantify safety issues associated with the audited design.
This RSA usedIHSDM to evaluate design consistency, compliance withselected design policy values,and to predict the expected safety of the future roadway. Specifically, theproposedalignment was analyzed using:
- the IHSDM Policy Review Module (PRM) to identify two locations where stopping sight distancedid notappear to meetminimum sight distance requirements. It is important to note that an RSA is not simply a check that design standards have been met. Therefore, minimum policy checks using IHSDM were limited to sight distance policy checks. This enabled the RSA team to observe conditions in the field that IHSDM identified as having a sight distance issue.
- theIHSDM Crash Prediction Module (CPM) and five yearsof crashdata (2000-2004) to identify the potential fora futureincrease incrash frequency attwo intersections along the alignment;
- the IHSDM Design Consistency Module (DCM) to estimatefree flow 85th percentile operating speeds betweensuccessive alignment elements, as a measure of design consistency. The results from the DCM suggested that, with the proposed improvements, the alignmentof US 97 was reasonably consistent.The DCM found no locations requiring speed reductions greater than 6 mi/hr entering a curve, whichwasconsidered the upper limit for good consistency. There were however, two horizontal curves where theDCM module identified speed differentials approachingthis limit,andthe PRM module identified insufficient stopping sight distances. The RSA team flagged the locations where the combination ofdesign-consistency and sight-distance issueswas found for the Design Team's further consideration.
The ability to quantify values associated with design issues such as stopping sight distance, and to estimate futurecrash frequencies based onthe road re-design, enhanced thevalue of the RSAby demonstrating themagnitude ofthe 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 in expected crash frequencies. Quantifyingthese 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.
See also the discussion of “Key Factors for Success” and “Lessons Learned” in the main text.
3IHSDM currently includes five evaluation modules: Crash Prediction Module (CPM), Design Consistency Module (DCM), Intersection Review Module (IRM), Policy Review Module (PRM), and Traffic Analysis Module (TAM).
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Program Contact
Becky Crowe
Program Manager
rebecca.crowe@dot.gov
804-775-3381
Training
Heather Rigdon
RSA Program Support
Heather.Rigdon.ctr@dot.gov
703-676-6828
Technical Assistance
K. Craig Allred
Transportation Specialist
craig.allred@dot.gov
720-963-3236
What’s New
Newsletter: Winter 2012, Volume 3, Number 3
Federal and Tribal Lands Road Safety Audits: Case Studies
RSA Toolkit for Federal and Tribal Lands
Highlights
RSAs For Safety
Transportation professionals employ audits to scrutinize roadways for safety issues-and reduce crashes, injuries, fatalities, and costs in the process. Artice by Lousia Ward.
RSA Peer-to-Peer Assistance
FHWA has a new peer-to-peer program for RSAs where you can receive on-site or over the phone assistance on an RSA from a peer for no charge.
