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National Cooperative Highway Research Program (NCHRP) Reports

Reports are the main product of the research project and are often written as guidebooks or manuals. Supplemental project material—such as appendixes, which describe technical details, information-gathering activities, or survey instruments; glossaries; and bibliographies—are disseminated online as web-only documents.

This page includes links to NCHRP Reports that have been released since June 2001. To search for older publications visit the TRB Online Bookstore or TRB Publication Index.

Guidelines for Treatments to Mitigate Opposite Direction CrashesGuidelines for Treatments to Mitigate Opposite Direction Crashes
May 16, 2022
From 2016 through 2018, there were more than 19,200 vehicles in the United States involved in opposite direction crashes that resulted in a fatality. Approximately 68 percent of these crashes occurred on two-lane roadways. The TRB National Cooperative Highway Research Program's NCHRP Research Rep...

Guide to Pedestrian AnalysisGuide to Pedestrian Analysis
February 18, 2022
Roadway designs and signal phasing that address the safety of all road users are being implemented in many cities around the country. As part of this, accurate methods for estimating pedestrian volumes are needed to quantify exposure and, in turn, evaluate the benefits of pedestrian safety measur...

Guidelines for the Development and Application of Crash Modification FactorsGuidelines for the Development and Application of Crash Modification Factors
November 17, 2021
Crash modification factors (CMF) provide transportation professionals with the kind of quantitative information they need to make decisions on where best to invest limited safety funds. The TRB National Cooperative Highway Research Program's pre-publication draft of NCHRP Research Report 991: Gui...

Guidebook for Effective Policies and Practices for Managing Surface Transportation DebtGuidebook for Effective Policies and Practices for Managing Surface Transportation Debt
April 22, 2022
The passage of Dodd-Frank and the COVID-19 pandemic are among the factors that have made the environment for tax-exempt debt issuers increasingly challenging and complex. The TRB National Cooperative Highway Research Program's NCHRP Research Report 990: Guidebook for Effective Policies and Practi...

Rural Transportation Issues: Research RoadmapRural Transportation Issues: Research Roadmap
September 27, 2021
Although only 19% of the population lives in rural areas, more than 70% of the U.S.’s four million miles of roadways are in rural areas. The rural transportation system also includes numerous airports; railways; inland and coastal waterways; rural and intercity buses; and bicycle, pedestrian, and...

Ruggedness of Laboratory Tests for Asphalt Mixture Cracking ResistanceRuggedness of Laboratory Tests for Asphalt Mixture Cracking Resistance
March 16, 2022
Cracking is a primary distress mode of asphalt pavements that creates the need for their rehabilitation. All types of asphalt pavement cracking—thermal, reflection, fatigue, and topdown— are affected by numerous factors and their interactions. The TRB National Cooperative Highway Research Program...

Implementation of the AASHTO Guide for Enterprise Risk ManagementImplementation of the AASHTO Guide for Enterprise Risk Management
March 8, 2022
The AASHTO Guide for Enterprise Risk Management , published in 2016, defines enterprise risk management as “the formal and systematic effort to control uncertainty and variability on an organization’s strategic objectives by managing risks at all levels of the organization.” The TRB National Coop...

Integrating Effective Transportation Performance, Risk, and Asset Management PracticesIntegrating Effective Transportation Performance, Risk, and Asset Management Practices
January 3, 2022
Research and practice in the areas of transportation performance, risk, and asset management have added to the tools, methods, and strategies available to state departments of transportation and other transportation agencies. Fundamentally changing the culture of a transportation agency and integ...

Breaking Barriers: Alternative Approaches to Avoiding and Reducing Highway Traffic Noise ImpactsBreaking Barriers: Alternative Approaches to Avoiding and Reducing Highway Traffic Noise Impacts
January 21, 2022
The most common approach that state departments of transportation (DOTs) use to address highway traffic noise impacts is noise barriers—usually noise walls. The TRB National Cooperative Highway Research Program's NCHRP Research Report 984: Breaking Barriers: Alternative Approaches to Avoiding and...

Reliability of Crash Prediction Models: A Guide for Quantifying and Improving the Reliability of Model ResultsReliability of Crash Prediction Models: A Guide for Quantifying and Improving the Reliability of Model Results
December 16, 2021
The AASHTO Highway Safety Manual (HSM) provides fact-based, analytical tools and techniques to quantify the potential safety impacts of planning, design, operations, and maintenance decisions. The TRB National Cooperative Highway Research Program's NCHRP Research Report 983: Reliability of Crash ...

Relationships Between the Fatigue Properties of Asphalt Binders and the Fatigue Performance of Asphalt MixturesRelationships Between the Fatigue Properties of Asphalt Binders and the Fatigue Performance of Asphalt Mixtures
February 4, 2022
Traffic-associated fatigue damage is one of the major distresses in which flexible pavements fail. This type of distress is the result of many thousands—or even millions of wheel loads passing over a pavement. The TRB National Cooperative Highway Research Program's  NCHRP Research Report 982...

Guidelines for Quantifying Benefits of Traffic Incident Management StrategiesGuidelines for Quantifying Benefits of Traffic Incident Management Strategies
February 4, 2022
Ensuring a coordinated response to highway crashes and other incidents is vital to protecting public safety, keeping traffic moving, and reducing environmental impacts. The TRB National Cooperative Highway Research Program's NCHRP Research Report 981: Guidelines for Quantifying Benefits of Traffi...

Attracting, Retaining, and Developing the Transportation Workforce: Transportation PlannersAttracting, Retaining, and Developing the Transportation Workforce: Transportation Planners
December 3, 2021
For public agencies, attracting qualified, technically competent, culturally sensitive, and motivated planning staff can be challenging in a competitive landscape. The TRB National Cooperative Highway Research Program's NCHRP Research Report 980: Attracting, Retaining, and Developing the Transpor...

Systematic Approach for Determining Construction Contract Time: A GuidebookSystematic Approach for Determining Construction Contract Time: A Guidebook
March 18, 2022
Contract time affects the cost of construction, traffic disruption and public inconvenience, the economic impact of projects to the surrounding areas, and schedule risks. The TRB National Cooperative Highway Research Program's NCHRP Research Report 979: Systematic Approach for Determining Constru...

Initiating the Systems Engineering Process for Rural Connected Vehicle Corridors, Volume 3: Model System Requirements SpecificationInitiating the Systems Engineering Process for Rural Connected Vehicle Corridors, Volume 3: Model System Requirements Specification
November 1, 2021
Rural corridors often include long stretches of highway with limited power, communications, and intelligent transportation systems (ITS) infrastructure; long distances between cities or services for travelers; different traffic and roadway characteristics; and significant incident-related rerouti...

Initiating the Systems Engineering Process for Rural Connected Vehicle Corridors, Volume 2: Model Concept of OperationsInitiating the Systems Engineering Process for Rural Connected Vehicle Corridors, Volume 2: Model Concept of Operations
November 1, 2021
Connected vehicle deployments in rural areas present opportunities for potential improvements in safety, mobility, and efficiency. It is important for the agencies that operate and maintain rural corridors to have a vision for connected vehicle deployment. The National Cooperative Highway Researc...

Initiating the Systems Engineering Process for Rural Connected Vehicle Corridors, Volume 1: Research OverviewInitiating the Systems Engineering Process for Rural Connected Vehicle Corridors, Volume 1: Research Overview
November 1, 2021
Connected vehicle technology has garnered substantial consideration and analysis in urban areas but less in rural settings due to infrastructure constraints. The National Cooperative Highway Research Program's NCHRP Research Report 978: Initiating the Systems Engineering Process for Rural Connect...

Access Management in the Vicinity of Interchanges, Volume 2: Research OverviewAccess Management in the Vicinity of Interchanges, Volume 2: Research Overview
February 15, 2022
The spacing of crossroads in the vicinity of interchanges can have operational and safety impacts on a street system. The deployment of access management strategies in these areas can also have potential influence on the economic vitality of a roadway network, but how best to balance these critic...

Access Management in the Vicinity of Interchanges, Volume 1: Practitioner’s GuideAccess Management in the Vicinity of Interchanges, Volume 1: Practitioner’s Guide
February 15, 2022
Careful management of access points along crossroads in the vicinity of interchanges can help enhance operational and safety performance at these complex, transportation facilities. The TRB National Cooperative Highway Research Program's NCHRP Research Report 977: Access Management in the Vicinit...

Resilience Primer for Transportation ExecutivesResilience Primer for Transportation Executives
August 6, 2021
CEOs of departments of transportation (DOTs) face many challenges, including some that will have serious impacts on people's mobility and safety, and possibly on the tenure of CEOs. Many of these challenges revolve around the resilience of the transportation system—how well it can withstand disru...

Transportation System Resilience: Research Roadmap and White PapersTransportation System Resilience: Research Roadmap and White Papers
September 24, 2021
Although the need for a more effective set of short- and long-term transportation resilience strategies is increasingly obvious and urgent, many knowledge gaps and institutional barriers still exist. The TRB National Cooperative Highway Research Program's NCHRP Research Report 975: Transportation...

Application of Crash Modification Factors for Access Management, Volume 2: Research OverviewApplication of Crash Modification Factors for Access Management, Volume 2: Research Overview
November 12, 2021
The 1st Edition, in 2010, of the AASHTO Highway Safety Manual revolutionized highway engineering practice by providing crash modification factors and functions, along with methods that use safety performance functions for estimating the number of crashes within a corridor, subsequent to implement...

Application of Crash Modification Factors for Access Management, Volume 1: Practitioner’s GuideApplication of Crash Modification Factors for Access Management, Volume 1: Practitioner’s Guide
November 12, 2021
While research and empirical evidence have shown positive safety and operational benefits associated with good access management practices, it can be challenging for transportation agencies to implement access management strategies on the basis of safety performance without methods and tools to q...

Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction: Phase III ResultsLong-Term Aging of Asphalt Mixtures for Performance Testing and Prediction: Phase III Results
November 15, 2021
The accurate characterization of the in situ aging of asphalt pavement materials over the service life of the pavement is of utmost importance to the implementation of mechanistic empirical (ME) pavement design and analysis methods. The TRB National Cooperative Highway Research Program's  NC...

Revised Clear-Water and Live-Bed Contraction Scour AnalysisRevised Clear-Water and Live-Bed Contraction Scour Analysis
July 16, 2021
Bridge waterways commonly narrow or constrict natural channels, forcing water to flow through a contracted area, thereby increasing the magnitudes of velocity and turbulent kinetic energy of flow passing through the waterway. If these increases cause erosion of the waterway boundaries, the contra...

Mainstreaming System Resilience Concepts into Transportation Agencies: A GuideMainstreaming System Resilience Concepts into Transportation Agencies: A Guide
June 24, 2021
Transportation officials recognize that a reliable and sustainable transportation system is needed to fulfill their agency’s mission and goals. The TRB National Cooperative Highway Research Program's NCHRP Research Report 970: Mainstreaming System Resilience Concepts into Transportation Agencies:...

Traffic Signal Control Strategies for Pedestrians and BicyclistsTraffic Signal Control Strategies for Pedestrians and Bicyclists
February 9, 2022
In the United States, traffic signal timing is traditionally developed to minimize motor vehicle delay at signalized intersections, with minimal attention paid to the needs of pedestrians and bicyclists. The unintended consequence is often diminished safety and mobility for pedestrians and bicycl...

LED Roadway Lighting: Impact on Driver Sleep Health and AlertnessLED Roadway Lighting: Impact on Driver Sleep Health and Alertness
July 29, 2021
Light emitting diode (LED) technology has revolutionized the lighting industry. The dimming and instant-on capabilities of these light sources along with their high efficiency have allowed lighting designers to overcome some of the limitations of previous technologies, particularly in roadway lig...

Asphalt Binder Aging Methods to Accurately Reflect Mixture AgingAsphalt Binder Aging Methods to Accurately Reflect Mixture Aging
April 30, 2021
Asphalt binders experience aging that occurs in two distinct stages under quite different conditions: (1) short-term during construction (plant mixing, storage, placement, and compaction) and (2) long-term during the service life of the pavement. The TRB National Cooperative Highway Research Prog...

Posted Speed Limit Setting Procedure and Tool: User GuidePosted Speed Limit Setting Procedure and Tool: User Guide
June 4, 2021
Several factors are considered within engineering studies when determining the posted speed limit, including the 85th percentile speed, which is based on the driving behavior of most drivers (85 percent). The 85th percentile speed is believed to represent a safe speed that would minimize crashes....

Mitigation of Weldment Cracking in Steel Highway Structures Due to the Galvanizing ProcessMitigation of Weldment Cracking in Steel Highway Structures Due to the Galvanizing Process
June 18, 2021
Structural supports for signs, luminaires, and traffic signals and other steel highway structures are generally galvanized to prevent corrosion and provide a long service life. However, recent investigations have revealed incidents of cracking in weldments of galvanized structures that appear to ...

Protocols for Network-Level Macrotexture MeasurementProtocols for Network-Level Macrotexture Measurement
June 21, 2021
Macrotexture, which influences vehicle-roadway skid resistance, refers to the texture of the pavement due to the arrangement of aggregate particles. Pavement surfaces are subjected to seasonal variations, and over time the embedded aggregates become polished due to the onslaught of traffic. Resea...

A Pandemic Playbook for Transportation AgenciesA Pandemic Playbook for Transportation Agencies
April 12, 2021
Understanding pandemics, their impacts to transportation, and potential effective response has become more important, not only for the response to COVID-19, but also if, as the World Health Organization warns, we are now “living in a time of viruses.” TRB's National Cooperative Highway Research P...

Proposed Modification to AASHTO Cross-Frame Analysis and DesignProposed Modification to AASHTO Cross-Frame Analysis and Design
February 8, 2021
Cross-frames are important structural components that serve many functions throughout the service life of steel I-girder bridges. Under repetitive load cycles caused by heavy truck passages, cross-frames and their connections can be susceptible to load-induced fatigue cracking if not properly des...

Entrained Air-Void Systems for Durable Highway ConcreteEntrained Air-Void Systems for Durable Highway Concrete
February 3, 2021
Laboratory testing and field experience have shown that highway concrete should be properly air entrained to resist the action of freezing and thawing, particularly in wet climates. Several gaps in the state of the knowledge still exist. The TRB National Cooperative Highway Research Program's NCH...

Proposed AASHTO Practice and Tests for Process Control and Product Acceptance of Asphalt-Treated Cold Recycled PavementsProposed AASHTO Practice and Tests for Process Control and Product Acceptance of Asphalt-Treated Cold Recycled Pavements
January 22, 2021
Pavement recycling is a technology that can restore the service life of pavement structures and stretch available funding for pavement rehabilitation. In general, pavement recycling techniques remix the existing pavement material and reuse it in the final pavement in the form of a stabilized laye...

Diverging Diamond Interchange Informational Guide, Second EditionDiverging Diamond Interchange Informational Guide, Second Edition
January 29, 2021
The diverging diamond interchange (also known as a double crossover diamond interchange) is a relatively new design to the United States. This design can increase throughput and safety without widening bridge structures. The TRB National Cooperative Highway Research Program's NCHRP Research Repo...

Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen MaterialsElectrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials
February 11, 2021
There is a need to identify new or improved laboratory and field test methods to measure the electrochemical properties of earthen materials surrounding buried or embedded steel elements. The TRB National Cooperative Highway Research Program's NCHRP Research Report 958: Electrochemical Test Metho...

Improved Test Methods and Practices for Characterizing Steel Corrosion Potential of Earthen MaterialsImproved Test Methods and Practices for Characterizing Steel Corrosion Potential of Earthen Materials
September 11, 2020
Electrochemical properties of earthen materials such as electrical resistivity, pH, salt concentrations, and organic contents are commonly used to characterize the corrosion potential of buried metal elements that are in direct contact with the surrounding soil. The TRB National Cooperative Highw...

Utilization Measurement and Management of Fleet EquipmentUtilization Measurement and Management of Fleet Equipment
January 29, 2021
State highway agency equipment fleet assets are vital to the delivery of agency programs, projects, and services. Measuring, monitoring, and reporting on asset utilization levels are necessary for the management of the equipment fleet and meeting the highway agency’s business needs. The TRB Natio...

Guidebook for Data and Information Systems for Transportation Asset ManagementGuidebook for Data and Information Systems for Transportation Asset Management
March 26, 2021
Effective transportation asset management (TAM) depends on having good data about the assets under management, their descriptions, current condition and history, functional performance, and the activities conducted to develop, maintain, improve, and rehabilitate them during the course of their se...