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 577
September 17, 2021
The degree of collaboration between state departments of transportation (DOTs) and metropolitan planning organzations (MPOs) on goals and performance targets for management of transportation assets varies. Collaboration may also involve investment decisions. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 577: Collaborative Practices for Performance-Based Asset Management B...
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NCHRP Synthesis 576
October 11, 2021
The nature of the transportation project-level air quality arena is evolving, and there are potentially significant impacts to project schedules and budgets should air quality issues arise. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 576: Practices for Project-Level Analyses for Air Quality compiles and documents information regarding existing practices related to proje...
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NCHRP Synthesis 574
October 01, 2021
Agencies must consider many factors, such as work zone duration and weather conditions, in selecting appropriate pavement marking materials to effectively guide drivers through work zones. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 574: Temporary Pavement Markings Placement and Removal Practices in Work Zones addresses the need for more knowledge on which different typ...
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NCHRP Synthesis 573
September 10, 2021
State departments of transportation (DOTs) and other state and local agencies have implemented integrated flood warning and response systems to mitigate the effects of floods. These systems are critical for staging personnel, deciding when to close roads, inspecting bridges, tracking floods throughout the state, and planning recovery. The TRB National Cooperative Highway Research Program's NCHRP S...
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NCHRP Synthesis 572
August 19, 2021
Permitted movements of oversize and overweight (OS/OW) loads traditionally occur during the daytime on weekdays to allow for adequate staffing support and safety-focused practices. Due to increases in traffic congestion, safety concerns over fleet mixes, and other factors, many states began allowing or requesting those movements to occur during off-peak traffic hours, including nights and weekends...
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NCHRP Synthesis 570
August 13, 2021
Although project closeout only entails a small portion of actual construction work, closing out highway construction projects for state departments of transportation (DOTs) is a complex and vital process that is a part of project delivery for highway construction projects. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 570: Practices for Closing Out Highway Projects from S...
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NCHRP Synthesis 569
August 25, 2021
Cold in-place recycling (CIR) is a process in which 3 to 4 inches of the existing asphalt pavement layers are pulverized, mixed with a recycling agent, and repaved in place. It provides agencies with cost-effective and environmentally friendly pavement maintenance and rehabilitation options for aged asphalt pavements. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 569: Pra...
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NCHRP Synthesis 568
July 09, 2021
Portland cement concrete (PCC) pavement joint sealing material technology has evolved in recent decades, and the effect of current joint sealant practice has not been well documented. Therefore, it is necessary to establish a standardized approach to joint sealant evaluation as well as to investigate the practice of joint sealant in PCC pavement design. The TRB National Cooperative Highway Researc...
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NCHRP Synthesis 567
July 30, 2021
Transportation Systems Management and Operations (TSMO) programs include elements of operations, planning, design, construction, maintenance, and safety. They are frequently complex and cross jurisdictional boundaries, involving traditional state departments of transportation (DOTs), local DOTs, and metropolitan planning organizations (MPOs), along with disruptive technology markets. The TRB Natio...
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NCHRP Synthesis 566
July 09, 2021
Bridge approach systems are used by state departments of transportation (DOTs) to form a smooth transition between the roadway and bridges. Adequate performance of bridge approaches is of extreme importance to transportation agencies as they affect both safety and the public perception of ride quality if the transition is not smooth. The TRB National Cooperative Highway Research Program's NCHRP Sy...
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NCHRP Synthesis 565
October 14, 2021
Pavement preservation is broadly acknowledged to provide network-wide benefits such as extending pavement life, enhancing system performance, reducing operation and maintenance costs, and improving safety. However, the performance of each pavement preservation project hinges on many factors. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 565: Maintenance and Surface Prepar...
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NCHRP Synthesis 564
May 06, 2021
State departments of transportation (DOTs) conduct planning and administer funding programs for the implementation of pedestrian and bicycle projects. The amount of federal funds available for these projects has grown steadily since 1992 under programs implemented as part of the Intermodal Surface Transportation Efficiency Act. The TRB National Cooperative Highway Research Program's NCHRP Synthesi...
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NCHRP Synthesis 563
May 05, 2021
Public–private partnerships (P3) allow public transportation agencies to attract private financing to deliver needed highway infrastructure and not have to wait until the required funding is fully in place via traditional state and federal sources. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 563: Performance Metrics for Public–Private Partnerships documents key performa...
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NCHRP Synthesis 562
May 03, 2021
The use of post-tensioning in concrete structures has allowed for the construction of economical long-span bridges. However, very limited information is available to guide bridge owners on how to maintain existing structures or, more specifically, to repair degraded post-tensioned structures. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 562: Repair and Maintenance of Pos...
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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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