Update of Intersection/Interchange Guidelines for Rural Expressways in Nebraska

Authors

• Aemal Khattak, University of Nebraska-LincolnFollow
• MM Shakiul Haque, University of Nebraska-LincolnFollow

ORCID IDs

Aemal J. Khattak: 0000-0002-6695-9842

MM Shakiul Haque: 0000-0001-5049-6006

Date of this Version

4-2026

Document Type

Article

Citation

Khattak, A. and Haque, M. (2026). "Update of Intersection/Interchange Guidelines for Rural Expressways in Nebraska", NDOT Research Report SPR-FY24 (032).

Abstract

Nebraska Department of Transportation (NDOT) staff frequently decide on changes to existing two-way stop- controlled (TWSC) intersections on rural expressway to alternative facilities, such as a restricted crossing U-turn (RCUT), a roundabout, a signalized intersection, or an interchange. As Nebraska makes progress toward completion of its expressway system, updated and defensible decision-making is essential for conversion of TWSC highway intersections. NDOT’s existing guidelines, developed in the 1990s, no longer reflect current operations, safety performance, or modern intersection designs.

This project updated and expanded NDOT’s guidance using contemporary traffic operational and safety data, combined with robust microsimulation and safety performance modeling. Traffic operations data were collected from TWSC, RCUT, roundabout, and signalized intersections on rural Nebraska expressways, as well as from diamond interchanges with stop-controlled and signalized ramps and a diverging diamond interchange. These facilities were modelled tin a microsimulation environment calibrated to Nebraska driving behavior, generating more than 11,500 scenarios covering a wide range of major road, minor road, and ramp volumes, turning combinations, and time-of-day conditions. The simulation results were used to develop statistical models for estimation of operational delays and predictions of the most suitable intersection/interchange alternatives.

Safety analysis incorporated crash data from TWSC intersections along rural expressways to develop a negative binomial model for estimation of crash frequencies across different traffic scenarios. The safety performances of alternative at-grade facilities were estimated using appropriate crash modification factors. This study used the FHWA “Interchange Comparison Safety Tool” to estimate crash frequency at conventional diamond and diverging diamond interchanges.

Furthermore, the research team compiled construction and retrofit cost information from national sources and Nebraska-specific projects for a comprehensive benefit-cost analysis.

The resulting guidelines integrated benefit-cost outcomes with operational and safety analyses, engineering judgment, and national best practices. These data-driven guidelines provide NDOT with a modern, consistent, and defensible framework for evaluating intersection upgrades, selecting interchange types, and assessing grade-separation needs on Nebraska’s rural expressways.