U.S. Department of Transportation
Federal Highway Administration
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Washington, DC 20590
Accident Models for Two-Lane Rural Roads: Segment and Intersections, FHWA-RD-98-133, October 1998.
This report is a direct step for the implementation of the Accident Analysis Module in the Interactive Highway Safety Design Model (IHSDM). The Accident Analysis Module is expected to estimate the safety of two-lane rural highway characteristics for existing and new projects. Several accident models are developed to estimate accident frequencies. The three main models are for road segments (with non-intersection accidents), one-way stop-controlled intersections with three legs, and two-way stop-controlled intersections with four legs. This report describes the collection, analysis, and modeling of accidents on rural roads in Minnesota (1985-1989) and Washington State (1993-1995).
Crash Models for Rural Intersections: Four-Lane by Two-Lane Stop Controlled and Two-Lane by Two-Lane Signalized, FHWA-RD-99-128, October 1999.
NCHRP Report 502: Geometric Design Consistency on High-Speed Rural Two-Lane Roadways. [PDF 810 KB]
Research objective was to develop guidelines that designers can use to improve the geometric design consistency of roadway features on high-speed, nonurban, two-lane roads. The guidelines are suitable for identifying specific problem locations and for analyzing alternative designs for new locations and for reconstruction projects. The scope of the proposed research was carefully defined in relation to the effort conducted by the same research team in the FHWA study, Design Consistency Evaluation Module for the Interactive Highway Safety Design Model (IHSDM). The FHWA study focused on geometric design consistency issues related to horizontal and vertical alignment.
Rural Expressway Intersection Safety. Tech Transfer Summary (Final Report, October 2004). [PDF 97 KB]
Project goal was to analyze crash characteristics for rural expressway, two-way, stop-controlled (TWSC) intersections, and synthesize safety strategies at these intersections. Researchers focused on determining the relative impact on crash rates of traffic volumes on both the major and minor roadways, and of intersection geometry (median width, presence of turning lanes, etc.).
Rural Expressway Intersection Synthesis of Practice and Crash Analysis, Final Report, October 2004. [PDF 3.02 MB)
Although rural expressways are safer than two lane roadways, expressway intersections can become a safety concern because vehicles are traveling at high speeds on multiple lanes. In Iowa, traffic safety engineers have already implemented conventional countermeasures to problematic stop-controlled expressway intersections, including installing approach rumble strips, STOP AHEAD, CROSS TRAFFIC DOES NOT STOP, and large STOP signs.
Three important conclusions can be drawn from this report. First, the safety performance of conventional two-way stop-controlled intersections on expressways declines precipitately as volumes on the minor roadway increase. Second, there are wide varieties of strategies that may be applied at expressway intersections (such as offset turn lanes) to improve safety at problematic intersections. Third, many STAs have implemented or are pilot testing several innovative strategies at expressway intersections.
Safety Impacts of Street Lighting at Isolated Rural Intersections Part II, Year 1 Report, Sponsored by Minnesota Department of Transportation and Minnesota Local Road Research Board, Final Report, December 2004. [PDF 2.03 MB]