Document Library

Spray-on rejuvenators are pavement preservation treatments intended to mitigate oxidative aging of asphalt binder in the nearsurface region of asphalt pavements. Although several highway agencies have evaluated these treatments, reported performance outcomes vary, and the Virginia Department of Transportation (VDOT) has limited documented experience with their use. Prior to this study, VDOT did not have an established specification or standardized evaluation framework for spray-on rejuvenators. This study was conducted to evaluate the feasibility and short-term field performance of spray-on rejuvenators under Virginia conditions and to support the development of guidance for potential future implementation. The scope included a comprehensive review of published literature, agency specifications, and state-of-practice documents, along with field trials conducted in the Lynchburg and Northern Virginia districts. Following completion of the Lynchburg District field trials, a special provision was developed to guide spray-on rejuvenator application practices and was implemented for the Northern Virginia District field trials.

Some types of geometric improvements that the Virginia Department of Transportation (VDOT) has begun to build in the past two decades, such as the reduction in the number of arterial access points, the replacement of a traditional four-way intersection with a roundabout, or a restricted crossing U-turn, or left-turn prohibitions, have elicited expressions of concern from businesses that operate on property adjoining the improvements. The business operators’ concern is that the improvement, by creating more circuitous access for motorists, will reduce customer traffic, with a consequent effect on the business’s revenue or on the value of the affected commercial parcel. VDOT has never compiled a quantitative, Virginia-specific dataset on how access changes have affected adjacent businesses. This study sought to fill that deficit by estimating the effects of changes in access on assessed parcel values before and after a VDOT reconstruction that altered the geometrics of an intersection or a road segment. Although business impacts could ideally be measured as taxable sales, such data were not feasible to obtain, and thus, assessed parcel values were the study focus. The study compiled information on 91 commercial properties fronting VDOT reconstruction projects and on 67 similar commercial properties nearby, not fronting the projects, at 30 VDOT projects in 16 counties and three independent cities. Information collected included two different measures of the change in motorized access—the number of additional turns and additional distance traveled—that resulted from construction and assessed real estate values during a nine-year window from four years before the year construction was completed to four years after the year of construction completion. This nine-year window was sampled to have a strong opportunity to capture the lagged effects of changes in access in case such changes were not immediately reflected in project assessments. The analysis found that, within the nine-year window, the changes in access that the investigators measured had no statistically distinguishable effect on the property value assessments of the commercial properties fronting the VDOT reconstruction projects.

A previous study by Blomberg and Cleven (1998) developed a pedestrian safety zone approach in Phoenix, Arizona, and Chicago, Illinois, focusing on pedestrian safety countermeasures in subsets of the cities that had experienced a high number of crashes involving people 65 and older. It proved efficient deploying countermeasures, significantly reducing the targeted pedestrian crashes in Phoenix. This original zone process, however, still needed significant resources to address the entire city, and required a relatively long time to plan and implement. The primary objectives of the present study included adapting the previous zones approach to be implementable quickly by cities using their resources and demonstrating the resulting low-cost pedestrian safety zones approach in several cities. Three cities—Gainesville, Florida; Kalamazoo, Michigan; and Saint Paul, Minnesota—agreed to demonstrate the low-cost zones approach. Each site prepared a case study report documenting the activities reported here. The approach appeared flexible and effective in all three cities. The discussion section of this report includes ideas for supporting more widespread use of the technique.

Fatigue failure of highway sign structures due to sustained wind-loading events has been recognized in many states. In fact, the American Association of State Highway and Transportation Officials specifies that the structural component should be designed for infinite life by maintaining wind-induced stress below their constant amplitude fatigue threshold. However, because existing structures are typically not designed for fatigue, the condition of all critical and fatigue-prone components must be evaluated for safety. Visual inspection requires extensive time and effort and may not detect unnoticed fatigue cracks, so growing attention has focused on analytical inspection tools to examine all critical members and connections for remaining fatigue life to ensure public safety. The reliability of these analytical tools depends on the accuracy of wind-loading models applied during the life span of the structure. This study devised a fill-interpolate-extend approach to furnish a wind-loading data ensemble for the duration of analysis. The ensemble established a reliable synthetic wind model to generate fatigue cycle counts. In addition, a comprehensive analytical framework, including structural modeling, stress extraction/processing, and fatigue damage simulation, was integrated to yield an affordable tool that is applicable to various sign structures topologies. The resulting software for non-cantilever overhead structures as well as cantilever and butterfly assemblies were successfully verified to predict real cases for fatigue damage, reflecting the in-situ condition of the structures.

Traditional crash-based intersection monitoring fails to capture the critical near-miss events that precede collisions involving vulnerable roadway users (VRUs). To provide a proactive alternative, this report investigates how emerging roadside LiDAR and AI/ML technologies can enhance intersection safety observability through three interconnected research thrusts. First, an infrastructure-based sensing survey identifies LiDAR as a premier primary modality due to its high geometric precision and robustness under varying lighting conditions. Second, a systematic study simulating vertical beam loss across six 3D detection architectures establishes a critical 20% beam-loss maintenance threshold. Beyond this point, VRU detection deteriorates rapidly, with concentrated, contiguous beam loss from sensor occlusion proving far more detrimental than dispersed loss.

Building upon these foundational insights, the third thrust introduces a real-world application via an end-to-end, auditable safety-analysis framework deployed at a signalized intersection in New York City. Utilizing a newly established, manually annotated 8,000-frame roadside dataset, the framework integrates 3D detection, tracking, stabilization, and structured human-in-the-loop quality assurance to convert raw sensor data into defensible near-miss evidence. A heavy vehicle-bicycle interaction case study demonstrates that contrasting direction-agnostic and longitudinal time-to-collision (TTC) metrics can successfully isolate lateral-intrusion conflict mechanisms that single-metric approaches miss. Together, these efforts validate roadside LiDAR as a scalable, interpretable, and highly defensible tool for proactive traffic safety management.

This publication is an official federal Traffic Safety Facts Research Note issued in May 2026 by the National Highway Traffic Safety Administration’s (NHTSA) National Center for Statistics and Analysis. The document details the methodology and structural framework of the National Occupant Protection Use Survey (NOPUS), which is the only annual, probability-based observational study in the United States designed to monitor daylight restraint usage. Rather than relying on self-reported driver surveys or post-crash police reports, the study's design utilizes trained field observers who physically stand at randomly selected roadside locations or ride along expressways to record actual seat belt behavior in real-time without stopping vehicles or interviewing motorists. The survey employs a complex, multistage probability sampling protocol—executed in partnership with Westat, Inc.—that annually catalogs observations of over 140,000 front-seat occupants across varying vehicle types, roadway classes, environmental settings, traffic densities, and regional jurisdictions. Ultimately, this publication acts as a highly standardized, objective statistical instrument used by safety planners to evaluate the long-term effectiveness of state legislative policies (such as primary versus secondary enforcement laws) and national occupant protection campaigns.

In recent years, the public transit industry has seen a significant trend toward establishing formal Customer Experience (CX) programs, with over 60 U.S. transit agencies creating programs to better understand rider needs, instill a customer-first approach to their services, and build ridership and community support. However, the rapid adoption of these programs has occurred without industry-wide standards, leading to a wide variety of organizational models and approaches.

TCRP Synthesis 187: Transit Agency Customer Experience Programs, produced by TRB’s Transit Cooperative Research Program, identifies emerging practices within transit agency CX programs across key themes, including program design, organizational structure, and performance measurement. In addition to results from an industry scan and survey, the report includes five case examples and highlights how CX programs are evolving within the transit industry, becoming a distinct professional specialization that increasingly relies on integrated data, performance measurement, and multidisciplinary collaboration. The report addresses the importance of strategic planning, investment, and the use of an “Influence Model” to guide CX initiatives. It also finds that CX programs are delivering measurable improvements for riders, and it identifies gaps and opportunities for future research to strengthen program effectiveness and advance the field.

Transportation construction activities involving in-stream work can mobilize sediment and elevate turbidity, which can affect sensitive aquatic species such as freshwater mussels. Although cofferdams are used to isolate construction areas and limit sediment mobilization, their installation and removal create some degree of sediment release as a result of unavoidable streambed disruptions. To support more informed impact assessments and survey requirements for aquatic species protection, this study determined the transport distances of sediment associated with the installation and removal of cofferdams. Related objectives were to compare the effect of cofferdam-related construction events on sediment loads and to document the factors that affect recovery times and sediment loads.

Streams associated with two bridge replacement projects in Virginia involving different but commonly used cofferdam types (sheet pile and sandbag or Jersey barrier) were instrumented with 19 turbidity sensors positioned upstream and up to 2,600 feet downstream of construction. In addition to continuous turbidity monitoring, data collection included water sampling and field measurements used to determine suspended sediment concentration and site-specific rating curve development. Suspended sediment loads were calculated using stream discharge, suspended sediment concentration, and duration of cofferdam-related construction events.

Across both sites, peak turbidity increases occurred immediately downstream of the cofferdam, with values as high as 238 Formazin Nephelometric Units at Site 1 and 3,324 Formazin Nephelometric Units at Site 2, which returned to background levels within 50 to 100 feet downstream. Sediment loads attributable to construction ranged from 3 to 636 pounds, and for most cofferdam-related construction events, more than 75% of the sediment load occurred in the first 50 feet downstream. The use of sandbag or Jersey barrier cofferdams generated higher turbidity and sediment loads than sheet piles, largely because installation and removal required more streambed disturbance. For all cofferdam-related construction events, turbidity levels returned to background levels between 5 and 90 minutes. Sediment load calculations from evaluated precipitation events were one to three orders of magnitude higher than loads from cofferdam-related construction events.

The findings can help inform assessments of potential mussel impacts from in-stream projects involving cofferdams conducted under comparable conditions. It is recommended that the Virginia Department of Transportation’s Environmental Division share this report with the Virginia Field Office of the U.S. Fish and Wildlife Service and aquatic program staff of the Virginia Department of Wildlife Resources to support agency evaluation of area-of-impact determinations and associated survey requirements for projects comparable with those this study examines.

NCHRP Research Report 1183: Determining Fleet Mix and Vehicle Size in the Rural Transit Setting, produced by TRB’s National Cooperative Highway Research Program, addresses the complex decisions that rural and tribal transit agencies and state DOTs face when determining the appropriate mix and size of vehicles to serve their communities effectively. The report is designed to help these agencies make informed, data-driven decisions about vehicle type, size, and fleet composition. Through detailed analysis, the research captures the full range of factors that influence fleet planning and vehicle selection in rural transit systems.

NCHRP Research Report 1184: Post-Implementation Evaluation of Transportation Projects: A Guide, produced by TRB’s National Cooperative Highway Research Program, is intended to demystify, promote, and support the adoption of PIE by providing an eight step implementation framework. The framework encompasses both technical and organizational strategies to support enterprise-wide adoption. The guide and its accompanying spreadsheet-based tool are designed to help practitioners institutionalize PIE throughout the project development process, regardless of their organization's level of readiness or data maturity.

State departments of transportation (DOTs) operate in a data-rich environment where effective planning and management increasingly depend on integrating information from sources such as pavement and traffic data, financial systems, project platforms, and geographic information system (GIS) assets. Because this information is often fragmented across siloed systems, many DOTs are adopting enterprise data warehouses (EDWs), centralized repositories that aggregate and standardize agency data. Optimized for analytics and decision support, EDWs provide reliable information through dashboards, business intelligence tools, and other platforms. By creating an authoritative source of integrated data, EDWs can reduce redundancy, improve efficiency and coordination, support predictive modeling and scenario analysis, and help staff and leadership make faster, evidence-based decisions about system performance, investments, resilience, and traffic safety.

NCHRP Research Report 1190: Implementing an Enterprise Data Warehouse in Transportation: A Guide, produced by TRB’s National Cooperative Highway Research Program, provides a comprehensive, phased approach to help DOTs design, deploy, and maintain a sustainable EDW tailored to their unique business needs and technical environments. The report explores five core phases of EDW implementation: planning, design, implementation, validation and deployment, and sustainment. It also covers project management, a customizable maturity assessment framework, best practices drawn from case studies, and integration with emerging technologies such as artificial intelligence (AI) and machine learning (ML), computer-aided design and drafting (CADD) and building information modeling (BIM) platforms, and conversational AI.