Document Library

This article explores how transportation and land-use planners can establish Freight-Efficient Land Uses (FELUs)—land-use patterns designed to minimize both the private costs and external costs associated with moving goods, guided by the findings of NCHRP Research Report 998: Planning Freight-Efficient Land Uses: Methodology, Strategies, and Tools. The article describes the need for FELUs and long-term planning strategies to foster FELUs.

Over the past several decades, the U.S. vehicle fleet has shifted toward larger, taller, and heavier vehicles, raising questions about whether roadside safety systems remain aligned with real-world vehicle characteristics. This study evaluated the adequacy of the Florida Department of Transportation’s current 31-inch guardrail height standard relative to the previous 27¾-inch standard and recent guardrail failure outcomes in Florida. The research included a review of guardrail height practices, analysis of vehicle center of gravity, weight, and fleet composition trends, identification and classification of confirmed guardrail failure crashes, statistical comparison of failure patterns by guardrail height and vehicle characteristics, and an Annual Average Daily Traffic-normalized hot-spot analysis. Confirmed failures with known guardrail height were distributed in proportions consistent with statewide inventory prevalence, indicating no evidence that either height standard was overrepresented in the failure dataset overall. Vehicle center of gravity was significantly higher in Over failures than in Through failures, while vehicle weight was not a significant predictor of failure mode. Over failures were directionally less common at 31-inch installations than expected based on inventory proportions, but the difference was not statistically significant. The hot-spot analysis identified locations where repeated failures may warrant additional field or engineering review. Overall, the findings support continued use of the 31-inch standard while emphasizing continued monitoring of vehicle fleet trends, guardrail performance, site-specific failure conditions, and potential future design adaptations as the vehicle fleet continues to evolve.

TCRP Research Results Digest 120: On-Demand Transit: Quality of Service Measures and Standards, produced by TRB's Transit Cooperative Research Program, examines how transit agencies and other operators across North America assess the performance of on-demand transit services, with a particular focus on QOS. The digest identifies metrics and benchmarks used to evaluate these services and documents the development of the QOS framework for on-demand transit used in the Transit Capacity and Quality of Service Manual (TCQSM), Fourth Edition. TCRP Research Results Digest 120 summarizes one of 12 small research tasks conducted to support the development of new content for the TCQSM, Fourth Edition.

Roundabouts are widely acknowledged to be effective at reducing travel speeds. These lower speeds are one of the
reasons why roundabouts tend to experience significantly fewer injuries and fatalities as compared to other types of
intersection control. However, there is limited research as to how speeds vary between roundabouts, signalized, and all-
way stop-controlled intersections. To better understand these differences, this study compares travel speeds between
roundabouts, signalized, and all-way stop-controlled intersections in Minnesota. At signalized intersections, speed data
are analyzed separately for vehicles arriving during the red and green phases. Multiple linear regression models are
estimated to examine average speeds and the deceleration rates at the entry approach, as well as average speeds and
acceleration rates on the exit approach. The results show that drivers begin reducing their speeds further upstream of
roundabouts, and speeds are also lower downstream of the roundabout as compared to other intersection types. This
reinforces research on the traffic-calming effects of roundabouts. At signalized intersections, driver deceleration behavior
is dependent on the signal phase during arrival (later, more rapid deceleration during green arrival or earlier, gradual
deceleration during red arrival). In contrast, behavior is comparable to roundabouts at all-way stop-controlled
intersections, though drivers tended to brake nearer to the intersection at these locations. Ultimately, this study provides
insights into how intersection design can influence driver speed selection and achieve target speeds.

This manual describes a pavement design methodology, termed mechanistic-empirical (ME) pavement design. Based on engineering mechanics that have been validated with extensive road test performance data, this methodology provides the highway community with a state-of-the-practice method for the design and analysis of new and rehabilitated pavement structures. The manual guides pavement design engineers in making decisions using the AASHTOWare Pavement ME Design software, which includes an updated local calibration guide that replaces the publication, Guide for the Local Calibration of the Mechanistic-Empirical Pavement Design Guide, First Edition, published in 2010.

Engineers are increasingly turning to Carbon Fiber Reinforced Polymers (CFRPs) to repair aging, corroded steel bridges because conventional methods are heavy, labor-intensive, and time-consuming. While CFRPs offer a high strength-to-weight ratio and corrosion resistance, past research primarily tested ideal, smooth steel surfaces and unrepresentative environments rather than real-world, deteriorated structures.

This study evaluated how corrosion, pitting, hygrothermal aging, and chloride/environmental exposure affect the bond between steel and two types of CFRP (normal and ultra-high modulus) across laboratory tests and field sites in Virginia. It also evaluated fatigue performance and cost-effectiveness.

Departments of transportation (DOTs) manage extensive bridge inventories while facing increasing pressure from aging infrastructure, extreme weather events, and evolving federal requirements for risk-informed asset management. The Federal Highway Administration (FHWA) requires DOTs to develop and maintain Transportation Asset Management Plans (TAMPs) that address risk management for National Highway System (NHS) pavements and bridges. Although federal guidance emphasizes incorporating risk into asset management planning, practices for identifying, prioritizing, and integrating bridge-related risks vary widely among DOTs. These differences reflect variations in geographic hazards, network characteristics, funding constraints, institutional capacity, and data availability, making it difficult to standardize approaches for quantifying and incorporating risk into decision-making.

NCHRP Synthesis 667: Identifying Risks and Incorporating Them into Bridge Asset Management Planning, produced by TRB's National Cooperative Highway Research Program, documents current DOT practices for identifying, evaluating, and incorporating risk into bridge asset management planning and bridge management plans. The report examines the types of risks considered, the organizational and decision-making structures used to address them, the prioritization approaches employed, and the integration of risk-based priorities into bridge and transportation asset management planning. It also reviews practices for monitoring and recalibrating risk-informed decisions and considers how incorporating risk influences funding and resource allocation.

Employees of state departments of transportation (DOTs) face numerous and dynamic hazards while executing their job duties, including work near moving equipment, work near the traveling public, and work during and responding to natural hazard events. In response, DOTs deploy a wide variety of occupational safety training to provide their employees with the knowledge, skills, and abilities to execute their job duties safely. That wide variety includes various topics, various cycles for updating, various modes of delivery, and various metrics for deployment, among other related issues.

NCHRP Synthesis 665: Occupational Safety Training and Knowledge Sharing for State DOT Employees, produced by TRB’s National Cooperative Highway Research Program, examines how state departments of transportation develop, deliver, evaluate, and update occupational safety training programs. It documents agency practices related to training delivery methods, required training by job function and supervisory level, agencywide versus district-specific programs, and the use of safety data and performance metrics to guide training decisions. The synthesis also reviews approaches for onboarding new employees, measuring training effectiveness, gathering employee feedback, developing specialized training, and involving experienced staff in the creation of in-house training materials. In addition, it examines knowledge transfer planning and the extent to which safety training is provided by in-house staff, consultants, or third-party training providers.

Transportation infrastructure—including buried utilities, drainage systems, and culverts—is frequently subjected to significant external stresses arising from existing conditions and new construction, especially in urban environments where deformation and failures can lead to significant operational and safety consequences. Lightweight fills offer a viable strategy to mitigate these stresses by reducing imposed loads. This study investigates the use of lightweight fills, specifically Foamed Glass Aggregate (FGA), as a sustainable solution to support California Senate Bill 1 (SB1) efforts to repair and maintain culverts, as well as for new construction applications. A numerical investigation was conducted to evaluate the performance of culverts backfilled with FGA compared to conventional fills. Models were developed for reinforced concrete box culverts and corrugated steel pipe culverts, and parametric analyses were performed across a range of configurations. Results indicate that FGA significantly reduces soil stresses, structural demand, deformation, and settlement compared to conventional fills. This study also developed design and construction guidance and proposed updates to Caltrans manuals to facilitate implementation in practice. The findings demonstrate that FGA is an effective, sustainable alternative for improving culvert performance in California and beyond, helping agencies better address aging infrastructure and increasing construction demands.

Throughout their transit journey, travelers with full vision can easily use visual information in the form of digital content, maps, and signs to find their way. However, this information is often not usable by people who are blind or have low vision (B/LV) who may use public transit alone or in combination with other modes of transportation. Therefore, it is crucial for transit agency leaders and staff to thoughtfully design and provide accurate, timely, and usable information in ways that passengers with vision disabilities can use to successfully take transit trips. It is also critical for transit agencies to understand that information equivalency is not only a good practice; it is required by federal law.

TCRP Research Report 264: Providing Passenger Information to People Who Are Blind or Have Low Vision: A Guide, produced by TRB’s Transit Cooperative Research Program, provides transit agencies and their local partners with up-to-date guidance to help make passenger information accessible to people who are B/LV. The guide provides foundational information on B/LV, including the spectrum and prevalence of vision disabilities, beneficial tools and training, and the concept of the complete trip. It also addresses accessibility requirements and standards, as well as strategies for providing accessible passenger information through multiple channels, including digital resources and staff. Tools are provided to help transit agencies evaluate the accessibility of their current passenger information and identify opportunities for improvement. The guide and tools are not officially adopted standards and do not have the force of law or official policy. Throughout the report, B/LV refers to vision issues, up to and including full blindness, that make everyday activities difficult and cannot be corrected with glasses, contacts, medicine, surgery, or other standard treatments.

The U.S. Department of Transportation (DOT) seeks to eliminate roadway deaths and serious injuries (FHWA, 2025). Achieving this goal requires reducing vehicle crashes, particularly roadway departure crashes, which account for approximately 55% of all fatal crashes and 66% of fatal crashes on rural two-lane highways. Common countermeasures include centerline rumble strips (CLRS) and shoulder rumble strips (SRS), which help prevent lane and roadway departures and help reduce fatalities, injuries, and property damage. However, their use also raises concerns about the safety of other road users, including bicyclists.

NCHRP Research Report 1186: Impacts of Rumble Strips on Driver Behavior and Bicyclist Safety, produced by TRB’s National Cooperative Highway Research Program, provides guidance on the application of CLRS and SRS on high-speed, two-lane highways, with a focus on their effects on bicyclist safety. The report examines the safety impacts of CLRS and SRS on bicyclists traveling on rural high-speed, two-lane roadways and characterizes motorists’ behavior during interactions with bicyclists on roads where these treatments are present.

Highway infrastructure inspection helps ensure that construction meets plans, specifications, and material requirements while supporting the quality and longevity of transportation assets. Infrastructure owners are increasingly using emerging remote virtual inspection (RVI) technologies, including mobile devices, AI, machine learning, light detection and ranging, small uncrewed aerial systems, and remote imaging technologies such as augmented reality, virtual reality, and closed-circuit television. RVI technologies have numerous applications, including quantity estimation, verification and acceptance processes, payment scheduling, progress tracking, and the generation of as-built records to support future maintenance efforts. However, effective adoption requires thoughtful implementation and an understanding of each technology’s capabilities and limitations.

NCHRP Research Report 1172: Virtual Inspection Systems for Highway Construction Projects: A Guide, produced by TRB’s National Cooperative Highway Research Program, explores the fundamental principles, organizational strategies, governance mechanisms, readiness assessments, and practical examples for effectively integrating digital technologies and systems into RVIs. The guide is organized into four parts covering management guidance, technical reference, practical case studies, and key takeaways to support the understanding and implementation of RVI technologies.