Implementation Locations for J-Turn Intersections in Iowa

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Silbert, David
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Civil, Construction and Environmental Engineering

The Department of Civil, Construction, and Environmental Engineering seeks to apply knowledge of the laws, forces, and materials of nature to the construction, planning, design, and maintenance of public and private facilities. The Civil Engineering option focuses on transportation systems, bridges, roads, water systems and dams, pollution control, etc. The Construction Engineering option focuses on construction project engineering, design, management, etc.

The Department of Civil Engineering was founded in 1889. In 1987 it changed its name to the Department of Civil and Construction Engineering. In 2003 it changed its name to the Department of Civil, Construction and Environmental Engineering.

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  • Department of Civil Engineering (1889-1987)
  • Department of Civil and Construction Engineering (1987-2003)
  • Department of Civil, Construction and Environmental Engineering (2003–present)

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The safety of high-speed divided roadways is largely affected by the manner in which vehicles enter and exit from intersecting roads. Expressways include a combination of on-/off-ramps and traditional intersections using traffic signals and stop signs. These traditional intersections tend to cause more severe and fatal crashes, which is largely due to the high speed variance between conflicting vehicles. Consequently, state departments of transportation have recently focused their efforts on improvingsafety at expressway intersections using non-traditional configurations. One such example is referred to as a J-turn intersection, also known as a restricted crossing U-turn or superstreet intersection. J-turns have been implemented in various states, including Missouri, Maryland, and North Carolina, where it has been shown to provide many safety and operational benefits. The Iowa Department of Transportation has considered, but not yet implemented, any J-turn intersections. This study examined over 900 expressway intersections in Iowa to assess their suitability for conversion to a J-turn intersection. This assessment considered various characteristics including recent safety performance, projected operational performance, and geometric constraints. Based on the results, a prioritized list of the best candidate intersections for J-turn implementation was developed. This list provides useful guidance to inform intersection improvement projects throughout Iowa.
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