Date of Award
1-1-2025
Document Type
Thesis
Degree Name
M.S. in Engineering Science
First Advisor
Amir M. Molan
Second Advisor
Srinivas Pulugurtha
Third Advisor
Joseph E. Hummer
School
University of Mississippi
Relational Format
dissertation/thesis
Abstract
At-grade intersections on high-speed highways can be hazardous, particularly where lower-speed vehicles from minor roads must cross fast-moving traffic on major roads. To address this, the Mississippi Department of Transportation (MDOT) converted more than 20 unsignalized rural and urban intersections to the Restricted Crossing U‐Turn (RCUT) configuration between 2012 and 2022. This study provides the first before-after safety evaluation of these implementations, applying three analytical approaches: naïve before-after annual crash frequency comparison, an Improved Prediction Method (that accounts for changes in duration and AADT in before vs. after period), and a rigorous Empirical Bayes (EB) framework considering two definitions of the intersection influence areas (RCUT-system vs. intersection-only). To facilitate the Crash Modification Factor (CMF) development, new local Safety Performance Functions (SPFs) were developed using nearby reference sites, and the results were compared with those derived from Highway Safety Manual (HSM) SPFs and state-specific SPFs.
Across all methods, full RCUT implementations yielded substantial safety benefits: RCUT-system CMFs showed reductions from 40% to 56% for total crashes and from 57% to 75% for fatal and injury (FI) crashes; intersection‐only analysis showed even safer conditions. Temporary RCUT installations using delineators demonstrated moderate crash reductions but were less effective than full RCUT designs. In addition to this before-after analysis, negative‐binomial (NB) regression modeling of post‐implementation data identified factors impacting crash frequency on the newly installed RCUT. Protective factors include longer left turn storage lengths, angled-curb channelization, and acceleration lanes, while larger major‐ and minor‐road volumes, bidirectional or signalized U‐turn openings, proximity to farms, more driveways, wider crossover lanes and extended offset distances elevate crash risk. Despite methodological differences, all analyses confirm that RCUT conversions markedly improve safety at high‐speed intersections in Mississippi.
Recommended Citation
Aryal, Gaurav, "Safety Effectiveness of Unsignalized Restricted Crossing U-Turn (RCUT) Intersections in Mississippi Using Empirical Bayes Before After Study" (2025). Electronic Theses and Dissertations. 3235.
https://egrove.olemiss.edu/etd/3235