Document Library

The objective of this research project was to identify the obstacles or impediments to successfully and reliably using HESC for structural bridge deck overlays on Oregon bridges and to develop the standards, specifications, processes, and practices necessary to using them on ODOT bridges. Rapid strength gain is a desired property for fast and efficient bridge deck overlay reconstruction. Three calcium sulfoaluminate (CSA) cement systems, an ASTM C 150 Type III ordinary portland cement (OPC), and a CSA-OPC blended system were evaluated in this research project for potential use as high early strength structural overlay materials for Oregon Department of Transportation (ODOT) concrete bridge decks. A high-performance concrete (HPC) mixture that is representative of ODOT bridge deck mixture designs from the early 2000s to present was also analyzed in this project. CSA cement systems performed satisfactorily when subjected to compressive strength tests, workability tests, curing tests, bond strength tests, early age cracking tests, freeze-thaw cracking tests, and thermal expansion tests when compared with HPC. Resistivity and formation factors of CSA concretes were measured and compared poorly to HPC resistivity and formation factors. While these values would normally suggest rapid rates of corrosion, the collected data is insufficient to conclusively indicate high corrosion rates since these tests were developed for OPC systems and may not be applicable to CSA systems. Additional work to elucidate the role of curing and conditioning of CSA systems is merited before definitive conclusions can be drawn regarding chloride-based corrosion in these systems.

In 2023, fatalities that involved workers on foot being struck by a vehicle accounted for 60% of all fatal highway worker injuries (National Work Zone Safety Information Clearinghouse, n.d.). Increasing the visibility of road workers to oncoming drivers may help reduce this crash risk. Wearable lighted apparel has the potential to increase the visibility of road workers, but its impact on visibility and any potential drawbacks are not well understood. Additionally, regulations and codes governing safety apparel and the use of lights within work zones do not specifically address personal lighted apparel, so it is unclear how it fits within current standards. This study sought to fill these gaps in knowledge. First, a market review was conducted to determine the range of lighted apparel options currently available. Second, a review of legal and regulatory barriers was conducted to determine what types of lighted apparel may be allowed under current standards. Third, a closed-course human factors study was conducted to gather both objective and subjective measures of worker visibility using a variety of lighted apparel options. Fourth, a field study was conducted to gather user feedback from road workers who used various lighted apparel devices.Fourteen different lighted apparel ensembles (including one no-lighting baseline ensemble) were selected for inclusion in the closed-course testing. The ensembles utilized three distinct lighted apparel devices (a lighted vest, a helmet light, and a shoulder-mounted light) in various configurations so that the impact of various aspects of lighted apparel could be tested. These included the lighting design (where the light was located on the worker), the light color (amber, green, red, or white), the flash pattern (flashing or steady-on), and intensity (high or low). Closed-course testing was conducted on the Virginia Smart Roads Highway test track. Three simulated work zones of varying complexity were set up. Within each work zone, an experimenter acting as a worker wore one of the selected ensembles. Participants drove an experimental vehicle along the test track and verbally indicated when they could first detect a worker in a work zone. The detection distance was measured using the differential GPS coordinates of the vehicle at the time of detection. Participants drove 15 laps to ensure that they saw each ensemble within each work zone. Results indicated that a combination of lights on the torso and lights on the head significantly improved detection distance in medium- and high-complexity work zones when compared to the standard retroreflective safety apparel. Green lights significantly improved detection distance across all conditions. Steady-on lights performed significantly better than flashing lights in the high-complexity work zone, but no difference was found in low- and medium-complexity work zones. No consistent effect of intensity was found. The field study equipped Virginia Department of Transportation and contractor personnel with a subset of five ensembles for use in their daily activities. Feedback was gathered through surveys and a focus group discussion. Users agreed that green was the most effective color. Users also tended to prefer the helmet-mounted lights over torso or shoulder-mounted lights. Users indicated a desire for more flashing options. Based on the results of this study, the research team recommends using a green, steady-on, helmet-mounted light to increase the visibility of road workers.

Low slump overlays are an important method to extend the life of bridge decks. The concrete mixture for low slump overlays has not changed in the last 30 years and these overlays show extensive cracking within a few years of placement. The objective of this research project is to minimize the cracking in low slump concrete overlays for mixtures placed with a volumetric mixer. These mixtures need to obtain a low permeability in the NT Build 492 and achieve a 28-day compressive strength of 4000 psi. The objectives of the research include:
i. Examining the most promising mixtures and documenting their performance
ii. Determining the impact of glass fibers to reduce cracking but still provide constructible concrete
iii. Implementing a mixture with and without fibers on separate field projects and documenting the construction and performance of low slump overlays
This work has already been implemented on six field projects, and based on talks with MnDOT engineers, these projects have been deemed a success for having a low amount of cracking while meeting specifications. Also, the contractors who have used these mixtures have requested to use them on other projects. This shows the success of the work.

This article examines how transportation agencies are adopting the Safe System Approach (SSA) to reduce road fatalities. Rather than attempting to eliminate all crashes, the SSA accepts that human error is inevitable and focuses on designing infrastructure, managing speeds, and building system redundancy so that accidents do not result in death or severe injury. Highlighting proven international successes alongside recent U.S. initiatives—such as roundabouts in Minnesota, road diets in Kansas City, and safer speed guidelines in Colorado—the authors show how prioritizing safety over driving speed and implementing practical, multi-layered design changes can transform road safety across communities.

This article summarizes key findings from National Cooperative Highway Research Program (NCHRP) Project 17-97, “Strategies to Improve Pedestrian Safety at Night” and the Safe Speeds and Safe Roadways pillars of the NCHRP Research Report 1157: Strategies to Improve Pedestrian Safety at Night guidance.

This Minnesota Department of Transportation report examines how local agencies balance safety, liability, and maintenance budgets when applying pavement markings to medium and low volume roadways.

This report provides a first look at 2025 pedestrian fatality data. Preliminary data have been adjusted slightly to account for historical underreporting. GHSA projects 6,732 pedestrians were killed in traffic crashes in 2025, a 7% decrease from 2024 and the third consecutive year with a decline.

The report also analyzes 2024 pedestrian fatality data from the National Highway Traffic Safety Administration’s (NHTSA) Fatality Analysis Reporting System (FARS). These are the most recent federal motor vehicle fatality data available and include specific information on crash characteristics – speeding, hit-andruns, alcohol impairment, time of day, roadway factors and vehicle types – that is not available in the 2025 state reported fatality numbers.

These analyses help explain when, where and why pedestrians are killed on U.S. roads, which can inform what countermeasures to use to help prevent future deaths. For example, in 2024, the percentage of both drivers and fatally injured pedestrians reported as distracted has increased significantly. This suggests additional efforts are needed to ensure people on the road are aware of their surroundings and take action to protect themselves and others.

Anthropogenic noise and light have been shown to impact wildlife behavior, distribution, movement, and population fitness
and survival. Traffic noise and light can inhibit wildlife use of areas adjacent to roads, impair wildlife perception of traffic
risks, and cause a barrier effect to wildlife occurrence and movement well beyond road edges. A critical action being taken
by states to repair wildlife movement across roadways is construction of wildlife crossings, theoretically providing a safe
passage across roads. Planning the location of theses crossings and to some degree their design currently does not take
into account traffic noise and light impacts on wildlife approaching the structures. The authors developed statewide
models of traffic noise and light intrusion into areas adjacent to state highways to aid understanding of wildlife responses to
noise and light and to aid locating and designing crossings to maximize wildlife approach and use. These models have the
added benefit of estimating traffic impacts as part of environmental analysis associated with delivering transportation
projects. The authors used the NoiseModeling software in QGIS and novel light-modeling tools developed in ArcGIS to
model the “noise-scape” and “light-scape” at high-resolution around California state highways. They used different
putative sources of traffic noise and light and model propagation (depending on traffic volumes) of both across adjacent
landscapes out to at least 1 kilometer. The authors tested the models in the field using transects of noise and light
measurements. The outputs were digital (raster) maps that showed the high and low impact areas.

There is a need to understand how transportation provision affects changes in travel including induced travel. Studies are especially needed in places where the increase in travel is substantial. Current research on induced travel in Tennessee has been largely lacking. Prior studies have often used the instrumental approach to isolate the effect of capacity enhancement on travel at the area-wide scale, thus, potentially masking the effect of additional capacity on a single road where improvements have been implemented. This project fills the identified research gaps. This study searches for and identifies instrumental variables at a disaggregate level to further examine the impact of changes in the transportation system on travel. This project operated at the level of individual facilities that experienced capacity enhancement such as road widening or constructing a new lane. The research conducted in this project has led to (1) obtaining local-based evidence of changes in travel after capacity enhancement implementation, (2) identifying drivers of induced travel, and (3) estimating the impact of adding road capacity on travel measured with vehicle miles traveled (VMT) via an instrumental variable (IV) approach at the facility level in Tennessee. Thus, transportation impact analyses will help planning agencies to better understand travel patterns and local transportation impacts of road capacity expansion in metro areas in Tennessee, assist with informed policy decision making, and develop regional and state transportation plans for regional and local transportation projects. The TDOT can use this
research as evidence-based estimates of travel changes in response to adding road capacity. The TDOT and regional agencies will have a better understanding of impacts of induced travel from the road capacity expansion projects and to improve performance, environmental sustainability, and direct capital investment for transportation in Tennessee.

Recycling highway construction materials and minimizing the use of virgin materials can reduce pavement life cycle costs, improve highway network conditions, conserve natural resources, and protect the environment. Although using recycled asphalt pavements (RAP) is beneficial in many aspects, aged binder in RAP gives rise to failure under repeated high axle loads and thermal effects. Thus, in Oregon, the use of RAP is currently limited to about 30% by weight of the mix.

For asphalt mixtures with a higher percentage of RAP, various strategic measures have been developed, including increased binder content, binder grade bumping, rejuvenators, and warm-mix asphalt (WMA) additives. However, selecting the most effective rejuvenators and WMA technology for
Oregon, developing methods and guidelines for choosing the proper amount of additives, and ensuring appropriate mixing to achieve high RAP mixes without compromising the performance of the asphalt pavements is crucial. In addition, practices for better managing the RAP stockpiles at the asphalt plants (including process controls) play an important role in the mix performance and need careful investigation.

This research study addressed the above-mentioned concerns through comprehensive experimental and analytical work, including the evaluation of performance, cost, and environmental benefits of using high RAP, incorporating the strategic techniques. The effect of RAP source variability, as well as inplant variability, has also been studied. Further, the results were confirmed through statistical analysis. Results of the analysis indicate that the performance of RAP mixtures depends on binder content, RAP content, and binder grade. Considering all aspects, the appropriate selection of a strategic technique could enable a 10% higher RAP than the current allowable limit in Oregon, ensuring adequate performance while lowering economic and environmental burdens.

Bridge strikes caused by over-height vehicles frequently damage steel girders and can reduce their load-carrying capacity, requiring rapid and reliable evaluation to ensure structural safety. Current evaluation practices rely on manual measurements that often require traffic disruptions and simplified assessment approaches that do not fully capture the effects of damage. In addition, finite element simulations are time-consuming and computationally intensive to develop for practical rapid evaluation. This study developed an integrated, data-driven framework for the inspection and assessment of damaged steel bridge girders. A semiautomated procedure was developed to process laser-scan point cloud data and extract displacement profiles along the girder span. Machine learning models were trained and validated using a dataset generated from finite element simulations informed by field measurements of actual bridge strike incidents to predict the residual capacity of damaged girders. Explainable artificial intelligence techniques were incorporated to interpret model predictions and identify key parameters influencing structural performance. Results demonstrated the framework’s capabilities in effectively capturing girder displacements, and for accurately and efficiently estimating the residual capacity, to support post-strike bridge evaluation. Measured girder deformations obtained from laser scanning can be used as inputs to the machine learning models for quantifying a girder’s capacity. The predicted capacity can then be incorporated into bridge rating software to compute rating factors, enabling rapid decisions on traffic restrictions and load posting. Additionally, the interpretability results can guide engineers in identifying critical design parameters and prioritizing repair actions.

The objective of this study is to evaluate whether the current SCDOT criterion requiring the roadway subgrade to be 1 ft above the design-event ditch water surface can be relaxed under selected geometric and soil conditions, particularly where larger shoulder widths and flatter side slopes increase horizontal separation between ditch water and pavement structure.