Transportation Engineering Commons^™

Guidance For Left-Turn Flashing Yellow Arrow (Fya) Implementation In Nebraska, Aemal Khattak, Li Zhao, Frank Selase Dzawu

Nebraska Department of Transportation: Research Reports

This research evaluates the safety performance of flashing yellow arrows (FYA) and driver behavioral responses in Nebraska, using data from 324 FYA intersections (Lincoln 160; Omaha 164) to develop evidence-based implementation guidance. The study addresses critical knowledge gaps in local driver acceptance patterns, the effectiveness of phasing configurations, and a comprehensive safety assessment that integrates crash and conflict analyses. The methodology employed four complementary analyses: (1) negative binomial crash frequency modeling of 3945 unique left turn crashes (2015-2024) across Lincoln and Omaha; (2) binary logistic regression of 948 gap acceptance decisions across 43 intersections; (3) linear regression of post-encroachment time …

Update Of Intersection/Interchange Guidelines For Rural Expressways In Nebraska, Aemal Khattak, Mm Shakiul Haque

Nebraska Department of Transportation: Research Reports

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. …

Ultra-High-Performance Concrete (Uhpc) For Bridge Deck Overlay And Structural Deck Repair, Jiong Hu, George Morcous, Akbota Aitbayeva, Ming Gerges

Nebraska Department of Transportation: Research Reports

Ultra-high-performance concrete (UHPC) is an advanced cementitious material known for its exceptional strength and durability, making it an ideal material for bridge deck overlays and repairs that address the common issue of premature deck deterioration. Conventional UHPC is typically flowable and self-leveling, which makes it unsuitable for deck surfaces with cross-slopes and/or sloped vertical profiles. Therefore, a highly thixotropic UHPC that responds well to vibration while remaining stable on sloped surfaces is needed for overlay applications. Mixtures with varying binder content, water-to-binder ratio, fiber content, and dosages of admixtures were developed and evaluated. Two of the most effective and economical …

Feasibility Of Using Recycled Waste Plastic In Concrete Pavements In Nebraska, Amasi Hajahja, Jamilla Teixeira, George Morcous

Nebraska Department of Transportation: Research Reports

Waste plastic (WP) is a growing environmental concern due to its non-biodegradable nature, large-scale production, and harmful impact on natural resources. With nearly 75% of WP in the U.S. ending up in landfills, effective recycling strategies are urgently needed. In parallel, the limited availability of natural aggregates highlights the need for alternative materials in concrete construction. This study investigates the feasibility of using recycled waste plastic (RWP) in concrete mixtures, both as aggregates and fibers for rigid pavement applications in Nebraska. Concrete mixtures were prepared by partially replacing natural fine aggregates with recycled plastic aggregates (RPA) at replacement levels of …

Characterization Of Sediment Loads And Size Distribution In Nebraska Roadway Runoff, Bruce I. Dvorak, David M. Admiraal, Pavel Shrestha

Nebraska Department of Transportation: Research Reports

The Nebraska Department of Transportation (NDOT) must manage sediment, and pollutant loads from roadway runoff to meet stormwater regulations. The SAFL Baffle, a hydrodynamic separator used by NDOT, depends on reliable estimates of total suspended solids (TSS) and particle size distribution (PSD). However, limited data exists for Nebraska roadways. In this study stormwater runoff was monitored at four NDOT-maintained sites, two in Lincoln and two in Beatrice, over 1.5 years to characterize TSS and PSD and to evaluate SAFL Baffle performance using the SHSAM model. Results showed large variability across sites and seasons. Median TSS ranged from 158 to 580 …

Assessment Of Winter Maintenance Performance Objectives Using Maintenance Decision Support System, Curtis L. Walker, Mark R. Anderson, Aemal Khattak, Thomas Kauzlarich, Abdul Farhan

Nebraska Department of Transportation: Research Reports

It is important for transportation agencies to assess their winter maintenance operations performance to identify areas for improvement and/or resource investment to maintain optimal levels of service, mobility, and safety. This study explores nine winter snowstorms in Nebraska during the 2023-2024 winter season across 20 road segments, 12 of which were along the Interstate-80 corridor. Datasets explored include meteorological information, traffic mobility insights, winter maintenance operations activities, and road conditions before, during, and after the periods of accumulating snowfall. Statistical analyses explored correlations and quantitative relationships among these datasets, while visual dashboards were developed to promote more qualitative considerations of …

Evaluation Of Critical Shear Strength Of Soils In Nebraska Based On Revised Cpt, Chung R. Song, Bashar Al-Nimri, Basil Abu Al Sha'r, Dhurba R. Pandey, Jongwan Eun, Seunghee Kim

Nebraska Department of Transportation: Research Reports

This study evaluated the “Fully Softened Shear Strength (FSSS)” of soils in Nebraska based on a revised Cone Penetration Test(CPT) method. FSSS is a unique strength condition that soils show substantially reduced strength during rainy seasons, eventually causing failure of slopes and other structures.

The revised CPT was adapted to inject water at targeted depths, inducing controlled moisture infiltration and capturing real-time soil softening over designated intervals of 30, 60, or 90 minutes. Through tip resistance (qc) and sleeve friction (fs) measurements under “in-situ” and “wet” conditions, the test effectively identified fully disturbed/low strength zones around the sleeve. Simultaneous sampling …

The Use Of Recycled Plastic In Asphalt Pavements: Feasibility Study, Isabella Bueno, Robert Rea, Jamilla Teixeira

Nebraska Department of Transportation: Research Reports

The plastics industry has been actively exploring new end-market opportunities for the more than 35 million tons of waste plastics generated annually. The use of recycled WP in asphalt presents an opportunity to improve pavement performance while reducing the growing amount of WP being landfilled or released into the environment. However, the use of WP in asphalt mixtures poses challenges due to variations in plastic composition and the presence of non-plastic contaminants. The absence of standardized procedures has resulted in inconsistent integration methods and unclear roles of WP within asphalt concrete (AC) mixtures. Therefore, the goal of this multiphase study …

Development And Evaluation Of Crashworthy Approach Guardrail Transition With Increased Span Length Between Concrete Bridge Rail And First Transition Post – Phase I, Tewodros Yosef, Qusai Alomari, Ronald K. Faller, Robert W. Bielenberg, Scott Rosenbaugh

Nebraska Department of Transportation: Research Reports

This study developed and evaluated a 34-in.-tall Nebraska Department of Transportation (NDOT) thrie-beam approach guardrail transition (AGT) with an increased span between the concrete buttress end and the first transition post. The objective was to accommodate a wide range of common obstructions near bridge ends, including abutments, wing walls, drainage features, and utilities. A survey of NDOT districts identified critical obstruction geometries and informed design criteria. Most NDOT districts indicated that a maximum span of about 4 ft would be sufficient, and some preferred spans up to 6 ft. To accommodate a wider range of obstructions, the first transition post …

Assessment Of Truck Parking Demand And Safety During Normal And Severe Weather Conditions In Nebraska, Nathan Huynh, Li Zhao, Zhenghong Tang, Aida Riahifar, Jahangeer Jahangeer

Nebraska Department of Transportation: Research Reports

This project examined truck parking capacity, demand, and utilization patterns along I-80 in Nebraska. The objectives were to (1) document the capacity of public and private truck parking facilities along I-80, (2) analyze spatial and temporal trends in parking demand, (3) develop models to predict occupancy at parking facilities, (4) identify clusters of undesignated parking during inclement weather, and (5) assess whether truck parking shortages contribute to truck-involved crashes. Within a one-mile buffer of I-80, 21 public facilities and 49 private facilities were identified. The spatiotemporal analysis of these public and private truck parking facilities using the National Agriculture Imagery …

The Impact Of Relative Bridge Width On Highway Crashes In Nebraska, Mujahid Ali Bahadur

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

This research examines how bridge width relative to the approach roadway affects crash occurrence on Nebraska highways. The Nebraska Department of Transportation-(NDOT) Bridge Design Manual sets minimum bridge widths based on roadway classification, traffic projections, and the American Association of State Highway and Transportation Officials’ (AASHTO) Load and Resistance Factor Design (LRFD) criteria. While these guidelines ensure structural and functional adequacy, they do not incorporate safety performance analyses based on crash data. This leaves an important gap in understanding how bridge and approach roadway width decisions influence safety outcomes.

This research has four objectives: (1) evaluate crash frequency across different …

Repair/Preservation Of Concrete Compression Members In Bridges Using Ultra-High-Performance Concrete (Uhpc), Mohammed Hedia, George Morcous

Nebraska Department of Transportation: Research Reports

As of 2024, approximately 36% of bridges across the United States require repair or replacement, with 7% classified as structurally deficient. The estimated cost to address these deficiencies exceeds $260 billion. In recent years, Ultra-High-Performance Concrete (UHPC) has emerged as a repair material for infrastructure preservation, drawing increased attention from transportation agencies and researchers worldwide. The Federal Highway Administration (FHWA) has notably advocated for UHPC’s adoption in bridge preservation initiatives, recognizing its exceptional mechanical properties and durability.

This report presents a comprehensive literature review on the application of UHPC as a repair and strengthening material for bridge compression members. While …

Resilience Of Interdependent Transportation And Healthcare Systems: A Simulation-Driven Framework Incorporating Social Equity And Facility Optimization, S. Yasaman Ahmadi

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

The overarching goal of this dissertation is to develop an integrated, simulation-driven framework to assess and enhance the resilience of interdependent transportation and healthcare systems before, during, and after natural hazards. By examining how spatial disruptions, social vulnerability, operational constraints, and infrastructure interdependencies affect access to and functionality of hospitals, this research offers a multifaceted evaluation of system performance under stress. This dissertation examines the impact of natural hazards, particularly floods, on the interdependent transportation and healthcare systems. The proposed approach combines and advances GIS-based network analysis, graph-theoretical modeling, and discrete-event simulation to evaluate system performance under different scenarios. The …

Groundwater Flooding On Highways In The Nebraska Sandhills: Applying Remote Sensing, Precipitation And Groundwater Modeling To Determine Depth, Cause And Frequency, Aaron R. Mittelstet

Nebraska Department of Transportation: Research Reports

Climate change significantly impacts infrastructure sustainability, particularly through shifts in precipitation patterns, intensity, and duration. These precipitation dynamics may increase the occurrence of surface water and groundwater flooding. Groundwater in the Nebraska Sand Hills (NSH), including the thickest portions of the High Plains Aquifer, extends close to the land surface in interdunal areas, making the NSH vulnerable to groundwater flooding. Recent events involving heavy precipitation, snow melt, and rising groundwater levels have caused prolonged highway flooding, disrupting transportation networks. This study estimates groundwater flood inundation depth, duration and frequency in the highways of NSH using remote sensing techniques and groundwater …

Nebraska Balanced Mix Design - Phase Ii, Farzad Yazdipanah, Mahdieh Khedmati, Jamilla Teixeira, Hamzeh Haghshenas

Nebraska Department of Transportation: Research Reports

This study aimed to propose a performance-based framework to evaluate highly recycled asphalt mixtures containing polymer-modified binders for potential use in a balanced mix design (BMD) specification in the state of Nebraska. For that, loose and compacted mixtures were directly collected from plant and field projects within a benchmarking study, subjected to an extensive experimental program. The laboratory investigation employed different monotonic tests recommended in BMD Phase 1, as well as the dynamic modulus test. Three long-term aging protocols were investigated in terms of their impact on the mechanical, rheological, and chemical characteristics of asphalt mixtures and binders. Moreover, field …

Stop Design: Rethinking The Approach To Public Transit's Architecture, Elizabeth M. Nielsen

Architecture Masters of Science Program: Theses

Public spaces are the foundation of our social health and wellbeing, but are often designed without considering the needs of the public, creating spaces that people do not feel encouraged to use. Just as public space design as a whole often falls short of serving the public, the same can be said for a subset of public space design, public transit stops. While they are public spaces created for the purpose of waiting, their design rarely reflects this.

Well-designed public transit stops are capable of both maintaining existing ridership and drawing in new riders. Most commonly, this design occurs at …

Drainage Area Limitations Of Single Watershed, Peak Flow Estimates From Nrcs Methods, Timothy A. Maughan, Rollin H. Hotchkiss, Riley Hales

Nebraska Department of Transportation: Research Reports

Most state Department of Transportation roadway design sections predict peak flow for culvert design using, amongst other approaches, Natural Resources Conservation Service (NRCS) TR-20 technology. Even though this technology is more than 50 years old, there are no clear guidelines for how large a single watershed drainage area may be while remaining appropriate for predicting peak discharge with this method. Our objective was to identify the drainage area where TR-20 peak flow predictions significantly deviate from flow frequency predictions. We developed flow frequency estimates for 130 small-area stream gage sites in rural Nebraska and compared the calculated return period discharges …

Hickory Street Square Revitalization, Spencer Knight, Grace Dungan, Tim Kula, Evan Lauritsen, Lindsey Mennenga

Honors Program: Senior Projects (Public)

The Hickory Street Square Revitalization Project seeks to transform a central public space in Sidney, Nebraska into a dynamic, community-oriented area that supports local events, economic activity, and cultural heritage. The project addresses six core objectives: 1) convertible street design, 2) parking lot reconfiguration, 3) public amenities, 4) event flexibility, 5) lighting and signage, and 6) old electric plant renovation. A conceptual design was developed by the design team (S.T.E.E.L. Sentinel Solutions) by synthesizing the most effective features of three preliminary alternatives, shaped further through community feedback and evolving project constraints. The final project design minimizes disruption to existing activity …

Mash Crashworthiness Of Work Zone Devices And Breakaway Luminaire Poles, Mohammadreza Rajaee

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

This thesis presents a study on the crashworthiness of two commonly-used roadside safety devices: Type II barricades and luminaire poles supported by TB1-17 transformer bases. The first part focuses on designing and evaluating a non-proprietary, Type II barricade that meets MASH criteria. A validated LS-DYNA model, based on a previously-tested Type III barricade, was used to guide the design. The proposed Type II system was evaluated through simulation and confirmed with full-scale crash testing. The second part of the study investigates luminaire poles supported by the TB1-17 transformer base. A previously-developed LS-DYNA model was updated and validated using test No. …

Development Of Timber Bridge Railing And Approach Guardrail Transition, Aaron Lechtenberger

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Timber bridges with transverse and longitudinal bridge decks are increasingly utilized across the United States. However, limited research exists to develop bridge railing systems for high-service-level roadways that meet current vehicular impact safety standards. In response to this gap, the United States Department of Agriculture - Forest Service -Forest Products Laboratory (USDA-FS-FPL), in collaboration with the Midwest Roadside Safety Facility (MwRSF), initiated a research program to develop, crash test, and evaluate higher-service-level bridge railings and approach guardrail transitions (AGTs) compliant with the American Association of State Highway and Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH).

This study continued …

Gravel Road Performance Enhancement, Bora Cetin, Kristin Cetin, Charan Sai Vangaveeti, Mehdi Bulduk, Md Mahir Asif

Nebraska Department of Transportation: Research Reports

Nearly 30% of roads in the U.S. are unpaved, significantly impacting rural connectivity with Nebraska alone having approximately 75% unpaved roads. This study systematically evaluates local materials to improve gravel road performance, reduce maintenance frequency, and decrease financial burdens on counties. Survey responses revealed that nearly 70% of counties follow NDOT specifications for gravel road design, while more than 90% lack knowledge of local material quality. The most common distresses identified were raveling, loss of crown, dust, and improper drainage. These findings indicate that construction practices rely heavily on experience, rather than systematic design, highlighting the need for a performance-based …

Application Of Cementitious Materials And Fiber Reinforcement To Enhance Lime Stabilization For Nebraska Shale Soils, Jongwan Eun, Seunghee Kim, Chung R. Song, Laith Ibdah, Kenaz Owusu

Nebraska Department of Transportation: Research Reports

Lime stabilization is a widely used technique to improve weak subgrades; however, its effectiveness under freeze-thaw cycles remains a critical challenge. This study investigates the incorporation of cementitious materials and fiber to enhance the mechanical properties and environmental resistance of lime-stabilized soils under such conditions. Two types of soil, gray shale (plasticity index of 37.8) and clay soil (plasticity index of 19.0) from Nebraska, were used. Stabilization mixtures included lime dosages of 0%, 3%, and 6% by weight, combined with either 10% fly ash or 3% and 6% cement by weight, and 0% and 1% fiber. The experimental program comprised …

Application Of Cementitious Materials And Fiber Reinforcement To Enhance Lime Stabilization For Nebraska Shale Soils, Jongwan Eun, Seunghee Kim, Chung R. Song, Laith Ibdah, Kenaz Owusu

Nebraska Department of Transportation: Research Reports

Lime stabilization is a widely used technique to improve weak subgrades; however, its effectiveness under freeze-thaw cycles remains a critical challenge. This study investigates the incorporation of cementitious materials and fiber to enhance the mechanical properties and environmental resistance of lime-stabilized soils under such conditions. Two types of soil, gray shale (plasticity index of 37.8) and clay soil (plasticity index of 19.0) from Nebraska, were used. Stabilization mixtures included lime dosages of 0%, 3%, and 6% by weight, combined with either 10% fly ash or 3% and 6% cement by weight, and 0% and 1% fiber. The experimental program comprised …

Updating Rainfall Zones And Intensities In Nebraska For Improved Design Of Non-Bridge-Sized Drainage Structures, Rezaul Mahmood, Tirthankar Roy, Chanchal Gupta, Kanak Kanti Kar, William Sorenson

Nebraska Department of Transportation: Research Reports

This study assesses the effectiveness of precipitation zones and Intensity-Duration-Frequency (IDF) curves used by the Nebraska Department of Transportation (NDOT) for designing drainage structures. Twenty stations were selected for the analysis of revised IDF curves out of forty-two stations. Datasets have been considered from the National Center for Environmental Information (NCEI). By Comparing the new curves with existing ones, the study efforts examine the frequency, duration and severe rainfall. The results show that the IDF curves for various zones and stations varied noticeably from one another. Also, noticed that Zone A and B shows lower rainfall intensities in short to …

From Equitable Access To Equitable Usage: Moving Towards Data-Driven, Evidence-Based Cycling Assets Management, Kewei Ren, Yunping Liang, Chun-Hsing Ho

Durham School of Architectural Engineering and Construction: Faculty Publications

Cycling is increasingly recognized for its wide range economic, environmental, and health benefits as a mobility option. However, disparities in the provision and the quality of bicycle infrastructure persists. Ensuring fair access and usage of these benefits for all presents a significant challenge. As a result, establishing effective methodologies to evaluate cycling equity is critically important. This paper synthesizes research on infrastructure asset management with a focus on equity considerations in bicycle infrastructure. A systematic review of 19 North American studies critically examines how existing research categorizes vulnerable populations and assesses fairness. The results reveal that most existing analyses focus …

A Statewide Geographic Information System (Gis) As A Predictive Tool For Locating Deeply Buried Archeological Deposits In Nebraska: Phase Iii-The Sandhills Region, Anthony L. Layzell, Rolfe D. Mandel, John Swigart, David T. Williams

Nebraska Department of Transportation: Research Reports

This project developed a GIS to assist with the identification of deeply buried cultural deposits in alluvial settings across the Sandhills region of Nebraska. Soil survey data, previous geoarchaeological investigations, landform position, and other information was used to rank the potential of any stream valley setting as low, low-moderate, moderate-high, or high potential to contain buried cultural deposits. While the presence of buried soils does not necessarily translate to presence of buried archeological sites, the potential for such sites is far greater in buried soils. The GIS can be used by NDOT and other agencies with statutory historic preservation obligations, …

Minimizing Take Of Threatened Rattlesnakes And Optimizing Project Review In Se Nebraska, Shaun Dunn, Dan Fogell, Colleen Rothe-Groleau

Nebraska Department of Transportation: Research Reports

The western massasauga (Sistrurus tergeminus) and the timber rattlesnake (Crotalus horridus) are protected under Nebraska Statute 37-801-811 and listed as threatened species. These species occur in the right-of-way (ROW) along several roads in Jefferson, Gage, Pawnee, and Richardson Counties which necessitates the need for added Environmental Review (ER) from Nebraska Department of Transportation (NDOT) staff and onsite surveys prior and during maintenance and construction to roadways. This project sought to minimize ER time, staff time, and increase the knowledge of these species in southeast Nebraska by:

1. Identifying precise locations of western massasauga brumation sites;
2. Mapping travel …

Accelerated Bridge Construction (Abc) Decision Tool, Phil Barutha, Marc Maguire, Elio Saldana, Fray F. Pozo-Lora

Nebraska Department of Transportation: Research Reports

This report investigates the creation and assessment of a decision-making tool developed to aid the Nebraska Department of Transportation (NDOT) in determining the suitability of the Accelerated Bridge Construction (ABC) method for bridge replacement projects. The tool utilizes the Analytic Hierarchy Process (AHP) to integrate different criteria, including Average Daily Traffic (ADT), Average Daily Truck Traffic (ADTT), detour time, railroad impact, economy of scale, and the use of typical details, which were found to be paramount in the decision-making process across the state. A sensitivity analysis was conducted to evaluate the tool’s performance and identify the most significant factors influencing …

Effect Of Antioxidant Additives And Recycling Agents On Performance Of Asphalt Binders And Mixtures – Phase Ii, Nitish R. Bastola, Muhammad Ahmad, Mahdieh Khedmati, Jamilla Teixeira, Hamzeh Haghshenas

Nebraska Department of Transportation: Research Reports

The use of reclaimed asphalt pavement (RAP) in combination with recycling agents (RAs) (i.e., rejuvenators or softening agents) has gained significant attention from the pavement industry as a sustainable pavement solution, reducing the carbon footprint of manufactured products through the conservation of energy and reduction on the use of raw materials. Current research has found that RAs can improve RAP recycled asphalt mixture’s cracking resistance, while being capable of maintaining their rutting resistance. However, there are some concerns about the effect of RAs on the moisture damage resistance and the long-term performance (aging) of these additives. The current need is …

Asphalt Binder Laboratory Short-Term Aging - Phase Ii, Farzad Yazdipanah, Ahmad Muhammad, Zahra Kamali Khanghah, Mahdieh Khedmati, Jamilla Teixeira, Mohammad Ghashami, Hamzeh Haghshenas

Nebraska Department of Transportation: Research Reports

This study examined the effectiveness of laboratory short-term aging processes for warm mix asphalt (WMA) binders using response surface methodology (RSM) with various combinations of aging parameters: time, temperature, airflow, and binder weight. The research aimed to enhance understanding of aging parameter efficacy and propose a modified laboratory short-term aging protocol that accurately simulates plant short-term aging in WMA binders. Additionally, the study explored the potential of thermal simulation techniques to model the heat transfer within asphalt mixtures during the compaction procedure. To achieve these goals, three WMA mixtures produced at 135 ºC were collected from plants, and their asphalt …