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Mid-America Transportation Center

NDOR Design Guidelines for Stop-Controlled Intersections along Curved, High-Speed Major Road Alignments

Final Report
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Researchers

  • Principal Investigator: Karen Schurr (kschurr1@unl.edu 402-472-2233)
  • Project Status
    Complete
    Sponsors & Partners
  • Nebraska Department of Roads
  • About this Project
    Brief Project Description & Background
    Multiple-lane approaches (MLA) controlled by stop signs are becoming increasingly common in Nebraska. However, conversion of single lane approaches of two-way stop-controlled intersections to multiple-lane approach (MLA) stop-controlled intersections may result in unsafe traffic conditions if the three-dimensional geometric features of the stopped approach aren’t appropriately designed. The alignment solution of using broken-back horizontal curves is one that attempts to optimize the geometric design of the roadway with respect to safety, operational efficiency, construction costs and maintenance efforts while minimizing the use of surrounding right-of-way. No guidance is currently available as to how the combination of broken-back curvature impacts drivers along the major road. The successful understanding of the problem could lead to guidelines that would assist designers in finding the appropriate length of the tangent segment between curves to provide these optimal conditions
    Research Objective
    The objective of this research is to investigate driver safety and behavior at two-way stop-controlled MLA intersections. The reason for the investigation is to gain a better understanding of potential sight distance limitations due to side-by-side stopped vehicles at stop signs, as described earlier.
    Potential Benefits
    This project will develop guidelines to assist designers in finding the appropriate length of the tangent segment between curves to provide optimal conditions for safety and may set the format for the solution of similar geometric problems that surface over time, resulting in a better solution for this situation and laying the groundwork for solutions in the future.
    Abstract
    Multiple-lane approaches (MLA) controlled by stop signs are becoming increasingly common in Nebraska. However, conversion of single lane approaches of two-way stop-controlled intersections to multiple-lane approach (MLA) stop-controlled intersections may result in unsafe traffic conditions if the three-dimensional geometric features of the stopped approach aren’t appropriately designed. This can be difficult because detailed traffic safety records of multiple-lane approaches at two-way stop-controlled intersections is lacking, and past intersection safety research has largely ignored this category of intersections. The research available pertaining to two-way stop-controlled intersections almost exclusively assumes a single-lane approach (SLA) to the stop signs on the minor road. The alignment solution of using broken-back horizontal curves is one that attempts to optimize the geometric design of the roadway with respect to safety, operational efficiency, construction costs and maintenance efforts while minimizing the use of surrounding right-of-way. No guidance is currently available as to how the combination of broken-back curvature impacts drivers along the major road. The successful understanding of the problem could lead to guidelines that would assist designers in finding the appropriate length of the tangent segment between curves to provide these optimal conditions. Combination of low traffic volume and complementary vertical geometry may result in the broken-back curve design being the optimal configuration in certain situations that could be defined by this research project.
    Project Amount
    $ 133,418