HFST Review

The Missouri Department of Transportation (MoDOT) has implemented High Friction Surface Treatment (HFST) in various locations across the state to reduce roadway departure crashes by improving pavement friction. To prevent premature failure and to ensure that the HFST performs adequately throughout the design life, this study evaluates the pavement distress and condition before and after the application of HFST. Along with the pavement distress and condition data, this study also evaluates the crash data of the HFST sections. Although analysis of distress data showed higher distress in some sections, it was the reflection of underlying distress, not the ‘failure’ of HFST, as observed from the ARAN images. Statistical analysis of the safety data revealed that HFST is around 66% effective in reducing crashes in wet conditions. Based on the evaluation of pavement condition and safety analysis, this study also provides guidance on the selection of future locations for the application of HFST.

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Report number: cmr 24-023
Published: December 2024

Project number: TR202219

Authors: Zafrul Khan, Jay F. Bledsoe, Ahmad Alhasan, and Hyung S. Lee

Performing organization: Applied Research Associates, Inc.

Effective Methods to Safely Communicate with Commercial Motor Vehicles

One critical aspect of a proactive approach to improving the safety of commercial motor vehicles (CMVs) involves how to communicate with CMV drivers safely and effectively through an electronic notification system (ENS). The objectives of this project are to: 1) conduct a review of existing ENS methods in use by CMV drivers, trucking companies, and the freight industry; 2) conduct a survey of selected state departments of transportation (DOTs) regarding their current practice in ENS for communicating with CMV drivers; 3) conduct a needs assessment brainstorming workshop with MoDOT and other stakeholders; and, 4) develop standards and specifications for data feeds consisting of traveler information critical for CMV operators. Results from the literature review indicate that several communication technologies have a wide range of applications for communication with CMV drivers. In their survey responses, all 18 responding DOTs indicated that they have not developed any data standards or policies for communicating information electronically to CMV drivers. Based on the discussion at the stakeholder workshop, a matrix of various facets (e.g., what is available, what is important and urgent, challenges) of types of information and technology used to convey that information to CMV drivers was developed. To address the challenges of diverse data streams for CMV drivers, a unified application programming interface (API) was developed to consolidate all relevant data (e.g., work zones, weather, congestion, traffic incidents, parking availability, weight and height restrictions) into a single, cohesive platform, providing CMVs with seamless access to critical information. The API, which was demonstrated through a web interface, ensures that CMVs and their operators can make well-informed, safe, and timely routing decisions. The API’s modular and scalable design offers flexibility to add additional features in the future.

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Report number: cmr 24-022
Published: December 2024

Project number: TR202410

Authors: Praveen Edara, Yaw Adu-Gyamfi, Henry Brown, Mark-Amo Boateng, Shawn Leight, and Joanne Stackpole

Performing organization: University of Missouri-Columbia

Load and Resistance Factor Rating Methodology Recommendations for Missouri Bridges

Traditionally, MoDOT performed bridge load ratings using the Load Factor Rating (LFR) methodology.  With the adoption of Load and Resistance Factor Design based Load and Resistance Factor Rating (LRFR) methodology, MoDOT is migrating to LRFR for rating bridges.  The primary goal of this study is to develop and recommend load posting policies using the LRFR methodology consistent with the current LFR policy.  The goal was accomplished using MoDOT-provided information on approximately one hundred reinforced concrete, prestressed concrete, and steel bridges each, and about thirty concrete culverts throughout the state and in different commercial zones.  The research conducted to compare the two rating methodologies has shown that the LFR and LRFR methodologies of rating differ in (a) bridges rated in LFR govern in interior girders while with the LRFR method, most bridges will govern in the exterior girders; (b) LRFR ratings are lower than the LFR ratings; (c) the number of posted bridges increased for LRFR over those required to be posted by LFR.  This points to a necessary change associated with the LRFR posting threshold to meet the current practice used by MoDOT. Recommendations based on the study of the various objectives applicable to each of the bridge/culvert types have been provided in this report.

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Report number: cmr 24-021
Published: November 2024

Project number: TR202122

Authors: Thiagarajan Ganesh, John Finke, John Myers, Bao Tran, Ronald Cheruiyot, and Nirav Khanal 

Performing organization: Missouri Center for Transportation Innovation

Developing Implementation Strategies for Risk Based Inspection (RBI)

This project's goal was to improve asset management through Risk-Based Inspection (RBI) practices. The research was intended to amplify the results of prior research that produced the Proposed Guidelines for Reliability-Based Inspection Practices. Under the new provisions of the National Bridge Inspection Standards (NBIS), bridge owners that implement a risk-based inspection (RBI) analysis can determine risk-based inspection intervals of up to 72 months for certain bridges. This research focused on developing implementation strategies to aid bridge owners in implementing these new NBIS rules. Reliability Assessment (RAP) meetings were held in six states during the research. Risk models were developed and applied to 60 sample bridges. These data were analyzed by comparing results with target values developed during the research. A data-driven methodology for analyzing the risk models based on bridge inventory data was developed. This methodology provides a means of calibrating and verifying the risk models. The method was found to be effective at analyzing the models and communicating their effectiveness. It was also found that there was consistency in the risk models developed by different RAP and these risk models were consistent with the target ranges developed through the research.

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Report number: cmr 24-020
Published: October 2024

Project number: TR201910/TPF-5(388)

Authors: Glenn Washer, Henry Brown, Robert Connor, and Mohammed Hammed

Performing organization: University of Missouri-Columbia

Safety Impacts of Fluorescent Yellow-Green Signs on Pedestrians

The Manual on Uniform Traffic Control Devices (MUTCD) specifies the use of yellow sheeting for pedestrian or bicycle signs and fluorescent yellow-green (FYG) for school signs, with an option for the use of FYG sheeting for pedestrian or bicycle warning signs. However, switching from yellow or fluorescent yellow (FY) to FYG for pedestrian and bicyclist signage could involve significant cost and effort for government agencies. The objective of this research study is to synthesize existing research and review the state of the practice regarding the use of FYG for pedestrian and bicyclist signs. The research methodology to meet these objectives includes a literature review, survey of departments of transportation (DOTs) and metropolitan planning organizations (MPOs), and follow up interviews with a subset of DOTs and MPOs. Findings from the literature review indicate that the results from previous research studies are inconclusive regarding the safety benefits of FYG (compared to yellow or FY) for pedestrian and bicyclist signs, and the research may be outdated. There is a wide range of agency practices for FYG signs for pedestrians and bicyclists among responding DOTs and MPOs, but many agencies allow FYG for pedestrians and bicyclists to some extent. Responding agencies have primarily switched to FYG for pedestrian and bicyclist signs based on a belief that the color stands out better and as part of other safety initiatives. None of the agencies that responded to the surveys indicated that they have performed any research studies to evaluate the safety performance of FYG signs for pedestrians and bicyclists. While a limited number of responding have seen improved safety performance (e.g., increased yielding compliance) with the use of FYG, the research did not identify significant and conclusive evidence regarding potential safety benefits associated with the use of FYG for pedestrian and bicyclist signs. Overall, the research findings suggest a need for additional research into the potential safety benefits of FYG signs for bicyclists and pedestrians.

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Report number: cmr 24-019
Published: October 2024

Project number: TR202416

Authors: Henry Brown, Praveen Edara, Carlos Sun, Daeyeol Chang, Zhu Qing, Priscilla Tobias, Jerrid Dinnen, Melissa Jiang

Performing organization: Missouri Center for Transportation Innovation, University of Missouri-Columbia

The Effect of Rubber Fills on the Performance of Infrastructure

One of the most environmentally friendly methods to recycle scrap tires is by shredding them into tire derived aggregate (TDA). TDA possesses desirable properties for various civil engineering applications and has been successfully used as fill material in numerous projects. To address the limitations of previous studies, 27 direct shear tests were conducted using a large-scale direct shear box (3 feet wide, 3 feet long, and 2 feet deep) on different TDA types mixed with soil. Additionally, 9 large-scale compressibility tests were conducted on the soil-TDA mixtures. TDA content was varied from 0 to 100% by weight in the soil mixtures. The direct shear tests were performed under confining pressures of 3.63, 7.25, and 10.88 psi. The results indicated that adding TDA to the soil significantly reduces the dry unit weight of the mixtures. When 25% TDA (Type A or Type B) was added to the soil, it provided the same shear resistance for the soil alone at all considered confining pressures. The compressibility test results showed that the inclusion of TDA increased the compressibility of the mixtures. It was observed that adding TDA to the soil contributed to a strain-hardening behavior in the mixtures. Also, adding 25% TDA reduced lateral earth pressure by 20% on average.

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Report number: cmr 24-018
Published: October 2024

Project number: TR202013

Authors: Mohamed Elashram, Ahmed Gheni, Mohamed ElGawady

Performing organization: Missouri University of Science & Technology

First and Last Mile Connectivity for Missourians

By closing gaps in transit systems or by complementing transportation services, first-last mile transportation services are integral in enabling access to employment opportunities as well as other key destinations. This research study examined first-last mile service programs across the United States and assessed existing conditions in Missouri to learn about the challenges and opportunities in providing first-last mile options supporting access to employment. This study showed that first-last mile services can address gaps in transportation systems, that different modes of transportation offer first-last mile service options to match local contexts and needs, and that partnerships between public agencies, mobility providers and local employers are key to develop first-last mile services supporting access to employment. 

To inform how first-last mile services can support Missourians’ access to employment, the team conducted a scan of over 50 first-last mile services across the United States, produced 15 case studies, and conducted 5 in-depth interviews with mobility providers. To understand what current conditions are affecting first-last mile issues in Missouri, the team developed an existing conditions analysis mapping transit and mobility services in Missouri, conducted in-depth interviews with 2 local transit agencies, and hosted a virtual forum with Missouri’s transportation stakeholders. The team summarized the findings from these research activities and presented recommendations to inform how State departments of transportation, local governments, and transit agencies can support first-last mile services for Missourians.

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Report number: cmr 24-017
Published: October 2024

Project number: TR202109

Authors: Alvaro Villagran, Peter Lauer, Hani Shamat, Luba Guzei, Nicky Althoff

Performing organization: Shared-Use Mobility Center

Evaluating Sedimentation Impacts to Freshwater Mussels

Transportation system construction activities can cause increased suspended and redeposited solids in adjacent water systems, which may adversely impact freshwater mussels. The objectives of this study are to evaluate the impacts of suspended solids on juvenile mussels including to establish the impact thresholds, to assess the effects of sediment deposition on adult and subadult mussels, to develop a particle tracking model to understand the particle transport behavior, and to evaluate the available mussel impact mitigation practices. The research methodology includes a literature review, a survey and interview on the current sediment management practice for mussel species protection in the nation, laboratory studies, modelling development, interviews with Missouri Department of Transportation (MoDOT) personnel, and engineering assessments. Results of the DOT surveys emphasize the need for further research to enhance understanding of the impacts of sedimentation on freshwater mussels. Laboratory experiment results suggest that (a) particles at low concentrations may benefit juveniles’ growth, while higher TSS concentrations (> 1000 mg/L) inhibited their growth; (b) adult mussels’ response to deposition were affected by burial depth, vertical water supply and flow direction, as well as mussel species, with the endangered Pink Mucket being the most vulnerable among all species tested. A one-dimensional model was developed to illustrate the spatial distribution of sediment transport, and results suggest that sedimentation varies with particle size, flow velocity and depth. A strategy for both streamside and instream best management practices was developed. The strategy incorporates lessons learned from other state DOTs and provides a link between both the mussel experiments and the modeling exercises and project site engineering.

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Report number: cmr 24-016
Published: September 2024

Project number: TR202109

Authors: Wenyu Zhu, Baolin Deng, Kathleen Trauth, Binbin Wang, Henry Brown, Qingqing Sun, Jeffery Steevens, James Kunz, and M. Christopher Barnhart

Performing organization: University of Missouri-Columbia

Friction Enhancements to Asphalt Pavement Surfaces

Maintaining the appropriate amount of pavement friction is critical for safe driving. Missouri Department of Transportation (MoDOT) has used high friction surface treatment (HFST) since 2013 to restore pavement surface friction where traffic has worn down pavement surface aggregates and to improve wet crash locations. Conventional HFST application consists of a polymer resin layer, which is used to bond the pavement with high abrasion, high angularity and texture, and polish resistant aggregates (e.g., Calcined Bauxite (CB) / (chat, slag)). Construction routines and pre-existing pavement conditions affect the performance of HFST made with polymer resin. Highway agencies examine existing pavement surface conditions before determining whether HFST can be used, as it is not intended as a repair for surface distress conditions, such as rutting. The relatively high cost of constructing, and removing, HFST with polymer resins along with the durability concerns due to existing pavement conditions, has led state agencies to consider high friction surface treatment with asphalt-based binders as an alternative. This research evaluates alternative asphalt binders for use in surface friction treatments. The research program evaluated the friction performance of HFST applications made with asphalt-based binders including newly developed modified asphalt binders. An updated Life-Cycle-Cost (LCC) EXCEL program was developed to conduct cost analysis based on the performance of the tested binder-aggregate combinations. The study showed acceptable asphalt-based binders for HFST applications and recommended continuing the development of asphalt-based binders to enhance the performance of HFST applications.

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Report number: cmr 24-015
Published: August 2024

Project number: TR202206

Authors: Alireza Roshan and Magdy Abdelrahman

Performing organization: Missouri University of Science & Technology

Analysis of Asphalt Mixtures Using Alternative Aggregate in SMA and Superpave

To identify locally available, cost-effective, and durable crushed coarse aggregates for Stone Matrix Asphalt (SMA) and high-level Hot Mix Asphalt (HMA) mixes, multiple well-distributed aggregates have been evaluated in this study as candidate aggregates, including traprock (control), chat, gravels, steel slag, limestone, and dolomite. Aggregate screening and durability evaluations were conducted to eliminate unqualified candidates. Subsequently, SMA and HMA mixtures were designed with qualified candidate aggregates following AASHTO R 46 and R 35, respectively. Performance verification included Hamburg Wheel Tracker rutting test (HWTT) and IDEAL-CT cracking test to finalize the mix designs, and balanced mix design methods (BMD) were used to complete the designs if the volumetric optimum designs failed to meet the performance requirements. The testing results showed that while the SMA and HMA mixes with traprock and gravel could satisfy both volumetric and performance thresholds. SMA and HMA mixes with blended aggregates (i.e., limestone and chat, and dolomite and chat) passed volumetric limits as well. For SMA and HMA mixtures with steel slag, the binder contents from the volumetric designs had to be increased to meet the cracking resistance requirements. Additional performance tests including fatigue and rutting on the Asphalt Mixture Performance Tester (AMPT), low-temperature Indirect Tensile (IDT) tests, and the Accelerated Friction Tests (AFT) were conducted to fully evaluate the mixtures’ performance and durability. Analyses on both the material and pavement structural levels were performed, and cost-effective analysis for projects with mixtures using different aggregates were also used in this study. The results indicated that mixes with alternative aggregates performed comparably to those with control aggregates.

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Report number: cmr 24-014
Published: August 2024

Project number: TR202205

Authors: Jenny Liu, Emad Kassem, Yizhuang David Wang, Bo Lin

Performing organization: Missouri University of Science & Technology

iTrain – Immersive Training of Department of Transportation Work Zone Inspectors using Virtual Reality

This report presents the development, implementation, and evaluation of Virtual Reality (VR) training modules designed to enhance work zone safety training for the Missouri Department of Transportation (MoDOT) staff. The project aimed to provide immersive, realistic, and interactive training environments that improve knowledge retention, engagement, and practical skills application. The developed VR training modules were integrated into MoDOT’s Advanced Work Zone Training and Flagger Training courses. For Advanced Work Zone Training, the modules focused on understanding typical applications and identifying deficiencies within work zones. For Flagger Training, the module emphasized hands-on practice of the 3-2-1 Cone Procedures. Both training programs incorporated measures of participants’ actions and post-training surveys. Feedback from the surveys indicated high levels of training effectiveness and participant satisfaction of the realistic work zone representations and ease of VR use. Behavioral performance measures, not feasible with traditional training methods, showed that participants effectively performed flagger operations and identified work zone deficiencies. Outreach efforts and hands-on demonstrations in other states further validated the positive reception of the VR training modules, highlighting their potential for broader adoption across other DOTs and agencies. The feedback collected was used to further refine the VR training program. In summary, the VR training modules enhance work zone safety training, offering a more immersive, interactive, and effective learning experience to supplement existing training.

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Report number: cmr 24-013
Published: August 2024

Project number: TR202118

Authors: Praveen Edara, Zhu Qing, Carlos Sun, Henry Brown, and Bimal Balakrishnan

Performing organization: University of Missouri-Columbia

Mitigating and Preventing MoDOT Safety-Related Incidents through Root-Cause Elimination and Utilization of Leading Safety Indicators

This report thoroughly investigates and analyzes the diverse factors influencing incident occurrence in work zone environments, aiming to identify areas where proactive planning can enhance incident mitigation. Drawing from an extensive review of existing literature on work zone safety, 37 factors affecting both public and occupational safety were identified. Two surveys were then conducted among MoDOT employees and contractors to assess the relative criticality of these factors on worker safety within work zones. Survey results highlight driver-related factors, such as the driver's level of attention and unsafe driving, as the most critical to worker safety in work zones. Additionally, MoDOT employees and contractors evaluated MoDOT’s performance on the studied factors. While MoDOT's performance received substantial ratings overall, contractors consistently rated it lower than MoDOT employees, indicating a divergence in perspectives between stakeholder groups. Notably, both groups identified the presence of law enforcement as a critical area requiring further improvement in Missouri work zones. Furthermore, MoDOT employees rated field compliance with safety policies and the overall safety culture in their workplaces. Variations in policy compliance were observed, with certain policies, such as those related to backing movements, requiring attention to improve adherence—a crucial aspect for occupational safety in work zone environments. Additionally, while MoDOT employees demonstrated strong knowledge of policies and safety procedures provided by MoDOT, they expressed lower satisfaction with the timely investigation of safety incidents and the effectiveness of subsequent improvements. This comprehensive analysis provides a benchmark for MoDOT and other stakeholders to address identified deficiencies and enhance work zone safety practices effectively.

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Report number: cmr 24-012
Published: August 2024

Project number: TR202212

Authors: Bahaa Chammout and Islam El-adaway

Performing organization: Missouri Center for Transportation Innovation

Safety Evaluation of J-turn Intersections in Missouri

The design of J-turn intersections has gained its prevalence in Missouri due to their demonstrated safety benefits. However, with the growing number of J-turns and the availability of more crash data, there is a renewed need to deepen the understanding of the safety performance of J-turns. This study presents a comprehensive safety evaluation of J-turn intersections, analyzing their effectiveness in reducing total and fatal & injury crashes using crash data from 47 J-turn intersections between 2005 and 2021. Employing a robust methodology including both comparison group and empirical Bayes analyses, this study assesses the impact of J-turns on crash reductions compared to traditional two-way stop-controlled intersections. Two methods were used because they had different tradeoffs such as data requirements, simplicity of implementation, and regression to the mean. The comparison group analysis revealed reductions of 46.6% in fatal and injury crashes and 44.4% in total crashes. Similarly, the empirical Bayes analysis supported these safety improvements, showing reductions of 51.4% in fatal and injury crashes and 40.3% in total crashes. Furthermore, crash frequency models developed for Missouri’s J-turn sites indicate that site characteristics such as loons, deceleration/acceleration lanes, and islands contribute to reduction in crashes. The study also includes detailed collision diagrams that outline crash locations and types at J-turn sites. The study findings provide insights and tools for MoDOT engineers as they consider J-turn design as a safety countermeasure at two-way stop-controlled intersections on rural highways.

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Report number: cmr 24-011
Published: August 2024

Project number: TR202320

Authors: Praveen Edara, Zhu Qing, Henry Brown, Carlos Sun, and Ho Jun Baek

Performing organization: University of Missouri-Columbia