Syntheses report on the state of the practice based on literature reviews and surveys of recent activities in critical areas. Syntheses also inform airport managers about innovations being used by others to solve problems.
Below are the latest 20 NCHRP Synthesis Reports that have been produced by TRB. A page highlighting
that have been released since June 2001 is available online. To search for older publications visit the
NCHRP Synthesis 561
March 10, 2021
Over the last decade, state departments of transportation (DOTs) have begun to use vehicle probe and cellular GPS data for a variety of purposes, including real-time traffic and incident monitoring, highway condition, and travel demand management. DOTs are also using vehicle probe and cellular GPS data to inform system planning and investment decisions. The TRB National Cooperative Highway Researc...
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NCHRP Synthesis 560
March 05, 2021
Digital terrain models (DTMs) are three-dimensional (3D) models of the ground surface showing natural features such as ridges and breaklines. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 560: Practices for Construction-Ready Digital Terrain Models documents processes and strategies used by state departments of transportation (DOTs) for the use and transfer of DTMs from d...
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NCHRP Synthesis 559
September 09, 2020
There is a wide disparity between the goals that state departments of transportation (DOTs) have for priced managed lanes and the public assumption for those goals. The public tends to be highly skeptical of priced managed lanes because the concept is difficult to explain to a nontechnical audience. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 559: Emerging Challenges to...
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NCHRP Synthesis 558
November 18, 2020
In March 2010, the U.S. Department of Transportation (DOT) released a policy statement supporting the development of fully integrated transportation networks. The policy is to “incorporate safe and convenient walking and bicycle facilities into transportation projects.” The TRB National Cooperative Highway Research Program's NCHRP Synthesis 558: Availability and Use of Pedestrian Infrastructure Da...
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NCHRP Synthesis 557
September 08, 2020
In 2017, the latest year for which data are available, 887 fatal utility pole crashes occurred in the United States, accounting for 914 fatalities. These numbers were about the same as those in recent years but lower than such fatality numbers from a decade or two ago. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 557: Utility Pole Safety and Hazard Evaluation Approaches ...
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NCHRP Synthesis 556
June 02, 2020
Current legislation and subsequent asset management rules require state departments of transportation (DOTs) to conduct statewide evaluations of roads, highways, and bridges that have required repair and reconstruction activities two or more times since 1997 due to emergency events as declared by the president of the United States or by a state’s governor. The TRB National Cooperative Highway Rese...
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NCHRP Synthesis 555
May 29, 2020
Scaling loose rock from highway rock slopes is an important aspect of improving rock slope safety in mountainous areas, according to input from 42 state departments of transportation and two regional divisions of the Office of Federal Lands Highway. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 555: Estimating and Contracting Rock Slope Scaling Adjacent to Highways docume...
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NCHRP Synthesis 554
August 10, 2020
Geotechnical instrumentation and monitoring technologies have been used to inform safety, operational, and treatment decisions for unstable slopes. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 554: Advances in Unstable Slope Instrumentation and Monitoring documents and synthesizes the state of practice for implementation and use of advancements in unstable slope instrume...
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NCHRP Synthesis 553
July 20, 2020
Pavement warranties have been common in the United States at various points in time, coming back into favor during the 1990s. While there is no national pavement warranty standard, agencies have developed their own specifications with varying criteria. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 553: Performance-Based Pavement Warranty Practices documents highway agency...
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NCHRP Synthesis 552
June 22, 2020
Performance testing of asphalt mixtures is becoming more widespread for a variety of reasons and with a variety of testing devices. The tests results are sensitive to the procedures used in preparation of the specimens. Guidelines exist for conducting the tests; however, they do not all provide uniform or comprehensive direction for fabricating test specimens. The TRB National Cooperative Highway ...
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NCHRP Synthesis 551
June 30, 2020
The TRB National Cooperative Highway Research Program's NCHRP Synthesis 551: Highway Hydraulic Engineering State of Practice documents significant changes in highway hydraulic engineering practices implemented by state departments of transportation (DOTs) over the past decade. The synthesis focuses on eight subtopics of highway hydraulic engineering: roadway drainage; culvert aquatic organism pass...
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NCHRP Synthesis 550
May 13, 2020
State departments of transportation often encounter public resistance to alternative intersections, with 86% of respondents in a new survey of state DOTs agreeing or strongly agreeing that public resistance hinders their implementation. Public resistance can vary among projects based on intersection type and whether the project was initiated at the local or state level. The TRB National Cooperativ...
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NCHRP Synthesis 549
March 24, 2020
Managing access connections to roadways is vital to safety and operational performance of roadways for all users. Given the separation of authority between state and local governments over land development and access, intergovernmental coordination is integral to effective access management. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 549: Incorporating Roadway Access M...
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NCHRP Synthesis 548
May 08, 2020
Sixty-eight percent of the states who responded to a survey indicated their agency has a documented process for as-built development. They said handwritten notes were the most commonly used method to capture as-built data (86%), followed by electronic notes (76%), and then photographs (33%). Some states use more than one option to capture as-built data. The TRB National Cooperative Highway Researc...
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NCHRP Synthesis 547
May 12, 2020
Geophysical methods provide a means to rapidly and economically characterize subsurface conditions and infer soil properties over a spatial extent that is not possible with conventional methods. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 547: Advancements in Use of Geophysical Methods for Transportation Projects evaluates the current state of practice in the use of geo...
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NCHRP Synthesis 546
April 24, 2020
Most U.S. state departments of transportation (DOTs) are collecting weigh-in-motion data with a wide variety of sensor types and using them in a variety of applications. Many agencies use WIM data to aid in pavement design, although most are not currently using a Pavement ME (mechanistic-empirical) Design application. WIM for bridge and asset management purposes is used much less often. The TRB Na...
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NCHRP Synthesis 545
June 16, 2020
Collecting paper load delivery tickets at highway construction projects is an outdated practice that exposes construction inspectors to many safety hazards. State transportation agencies (STAs) have looked for decades toward automating this process through electronic ticketing, or e-ticketing. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 545: Electronic Ticketing of Mate...
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NCHRP Synthesis 544
January 29, 2020
The past few years have seen some significant advances in concrete technology. For example, newer concrete incorporating advances in admixtures and cementitious materials has emerged. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 544: Concrete Technology for Transportation Applications documents how state departments of transportation select and deploy concrete technologi...
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NCHRP Synthesis 543
November 06, 2019
Estimates indicate that more than 14 million jobs—about 11% of civilian jobs in the United States—are related to infrastructure. Transportation has the potential to be a major U.S. job creator with projections to add 417,000 net jobs from 2012 to 2022. An additional 4.2 million workers will need to be hired to fill vacancies created by people leaving the transportation workforce. Transportation wo...
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NCHRP Synthesis 542
September 26, 2019
Freight investment project prioritization, which is used to assist in planning and programming decisions, differs widely in importance across states. One of the reasons for the difference in importance is the fact that freight projects are costly, and state departments of transportation (DOTs) face limited resources to implement them. The National Cooperative Highway Research Program's NCHRP Synth...
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