Cooperative Research Programs Series
Periodicals and Other Documents
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National Cooperative Highway Research Program (NCHRP) Synthesis Reports
Syntheses report on the state of the practice based on literature reviews and surveys of recent activities in critical areas.
Below are the latest 20 NCHRP Synthesis Reports that have been produced by TRB. A page highlighting NCHRP Reports that have been released since June 2001 is available online. To search for older publications visit the TRB Online Bookstore or the TRB Publication Index.
NCHRP Synthesis 624
March 21, 2024
Many state departments of transportation (DOTs) are undergoing organizational changes to address climate change. Changes range from hiring additional staff to creating new offices within the organizational structure of the agency. State requirements in the form of legislation, executive orders, and climate action plans are primary drivers for state DOT involvement with climate change. NCHRP Synthe...
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NCHRP Synthesis 619
March 08, 2024
State departments of transportation undertake hundreds of construction projects each year that affect, and are affected by, streams and rivers. These projects include replacement and rehabilitation of bridges and culverts, as well as new construction and rehabilitation of highways in stream corridors. While the hydraulic design standards for the completed bridge, culvert, or highway are well estab...
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NCHRP Synthesis 618
March 08, 2024
Women comprise only 15 percent of the transportation workforce, and this statistic declines in executive and leadership positions and does not reflect those who may not identify as men or women. For women of color, the numbers are even more disparate. NCHRP Synthesis 618: Advancing Gender Equity in the DOT Workforce , from TRB's National Cooperative Highway Research Program, documents current stat...
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NCHRP Synthesis 617
March 07, 2024
Surficial slope failures in highway fill embankments are shallow landslides that occur within the embankment fill, usually affecting only a portion of the slope’s height. These failures tend to occur after a vulnerable embankment slope is subjected to a triggering event. An embankment’s failure susceptibility generally depends on factors such as slope steepness, material composition, and ability t...
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NCHRP Synthesis 615
March 08, 2024
One tool utilized by some departments of transportation (DOTs) to improve safety performance is conducting road safety audits (RSAs), also known as “road safety assessments.” An RSA is a formal evaluation of the safety performance of an existing or future highway segment or intersection performed by an independent, multidisciplinary team. NCHRP Synthesis 615: DOT Practices on Road Safety Audits , ...
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NCHRP Synthesis 614
February 07, 2024
Post-construction stormwater best management practices (BMPs) are designed to reduce the amount of stormwater runoff, prevent erosion, and improve water quality by removing pollutants from stormwater. NCHRP Synthesis 614: Outsourcing Post-Construction Stormwater Best Management Practice Inspection and Maintenance Activities , from TRB's National Cooperative Highway Research Program, documents stat...
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NCHRP Synthesis 613
October 05, 2023
Contrast pavement markings (CPM) improve the visibility of pavement markings by providing better contrast with the pavement surface, especially on lighter-colored pavements. NCHRP Synthesis 613: Contrast Pavement Markings Practices , from TRB's National Cooperative Highway Research Program, documents current CPM practice by state departments of transportation.
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NCHRP Synthesis 612
October 19, 2023
Accurate and timely moisture measurement of soils, aggregates, and recycled materials is critical to properly compacting these materials. There are numerous methods for measuring the moisture content of the soil; some are laboratory-based, and some are done in-situ. NCHRP Synthesis 612: Moisture Measurement for Pavement Foundations and Slopes , from TRB's National Cooperative Highway Research Prog...
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NCHRP Synthesis 611
September 14, 2023
As freight transportation volumes have grown rapidly—further spurred by pandemic-driven e-commerce growth—state departments of transportation (DOTs) have become increasingly reliant on probe data to monitor freight infrastructure performance, manage demand, and understand freight infrastructure needs. NCHRP Synthesis 611: Use of Probe Data for Freight Planning and Operations , from TRB's National ...
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NCHRP Synthesis 610
July 13, 2023
Most state departments of transportation (DOTs) use social media to broadcast information and monitor emergencies, but few rely heavily on social media data. The most common barriers to using social media for emergencies are personnel availability and training, privacy issues, and data reliability. NCHRP Synthesis 610: Leveraging Social Media Data for Emergency Preparedness and Response , from TRB...
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NCHRP Synthesis 609
June 28, 2023
State departments of transportation (DOTs) are facing the challenge of maintaining and preserving local environmental systems while meeting transportation needs. Stormwater best management practices (BMPs) can help mitigate ecological impacts, and unmanned aerial systems (UAS) can be used to track, monitor, and document BMPs throughout their life cycle. NCHRP Synthesis 609: Use of Unmanned Aerial ...
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NCHRP Synthesis 608
July 19, 2023
In comparable private sectors, incentive and disincentive programs have effectively promoted safe behaviors by employees. However, state departments of transportation (DOTs) have unique limitations and restrictions on their ability to financially incentivize safe actions by highway construction and maintenance crews or, in some cases, implement corrective actions to disincentivize unsafe actions. ...
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NCHRP Synthesis 607
August 23, 2023
Road tunnels employ a multitude of functional systems that include a variety of equipment: lighting, ventilation, power supply, fire protection systems such as fixed fire-fighting systems, fire detection systems, communications systems and operational devices, supervisory control and data acquisition, closed circuit television, variable message signs, and radio. Maintenance of these systems is cri...
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NCHRP Synthesis 606
July 11, 2023
Most state departments of transportation (DOTs) are aware of the importance of integrating freight and active transportation, but there is a lack of coordination and standardized protocols for doing so. NCHRP Synthesis 606: Integrating Freight and Active Transportation into Policies, Programs, Plans, and Project Development , from TRB's National Cooperative Highway Research Program, documents stat...
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NCHRP Synthesis 605
June 26, 2023
State departments of transportation (DOTs) are working to deploy electric vehicle (EV) charging infrastructure, but face challenges and need AASHTO-type guidelines to help with deployment. NCHRP Synthesis 605: Electric Vehicle Charging: Strategies and Programs , from TRB's National Cooperative Highway Research Program, documents current strategies and practices in use by state DOTs to facilitate a...
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NCHRP Synthesis 604
May 25, 2023
Many bridges are built without accommodations for active transportation users and only serve motorized traffic. The pedestrians and bicyclists who rely on these bridges are exposed to safety-related concerns and their access to equal employment opportunities and essential services may be hindered. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 604: Practices for Adding Bic...
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NCHRP Synthesis 603
June 09, 2023
There are a variety of ways to achieve tolerances in steel bridge fabrication and erection. One common method is to use shop assembly, which is the process of assembling steel members in the shop before they are erected on site. Another method is to use oversize holes, which are holes that are slightly larger than the required size. NCHRP Synthesis 603: Practices for Steel Bridge Fabrication and E...
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NCHRP Synthesis 602
May 18, 2023
The increased frequency of extreme rainfall events, inland and coastal flooding, and other water-related stressors poses challenges to roadway infrastructure. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 602: Resilient Design with Distributed Rainfall-Runoff Modeling documents the practices of state departments of transportation on the use of DRRMs and identifies state D...
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NCHRP Synthesis 601
April 25, 2023
More than 15 years have passed since the U.S. transportation industry started its transition from allowable stress design (ASD) to load and resistance factor design (LRFD). For geotechnical design, the AASHTO LRFD Bridge Design Specifications includes provisions that allow state departments of transportation (DOTs) to develop their own design methods and resistance factors. The TRB National Cooper...
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NCHRP Synthesis 600
May 05, 2023
As-builts, inclusive of utility as-builts—which are the recorded representation of the built or maintained infrastructure and show the actual location, dimensions, geometry, and other attributes of the work as completed—can provide a baseline for new design projects by providing information on current transportation infrastructure and other facilities such as underground and overhead utilities. Th...
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