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 597
November 29, 2022
Micromobility vehicles and shared micromobility technologies are deploying rapidly in many cities across the United States and internationally. Lacking a standard definition, micromobility can include any small, personal transportation technology that travels slower than 20 to 30 miles per hour, may be motorized, and is frequently operated on pedestrian- or bicycle-oriented infrastructure (often, ...
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NCHRP Synthesis 596
September 09, 2022
There are few inventories of state investments in active transportation, at least partially because there is no federally mandated requirement to report on these investments. They are often accomplished as part of larger infrastructure projects, in order to realize the efficiencies inherent in making changes across modes on a network at the same time. The TRB National Cooperative Highway Research ...
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NCHRP Synthesis 595
September 09, 2022
Incompatibility between aggregate type and asphalt binder, presence of standing water or water under pressure in the pavement layers, and improper construction practices are some of the many factors that influence moisture susceptibility of flexible pavements. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 595: Practices for Assessing and Mitigating the Moisture Susceptibi...
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NCHRP Synthesis 594
September 23, 2022
Technology solutions are in no short supply for state departments of transportation across the United States. With advancements in geospatial accuracy, cost reduction for technology components, and a need for effective staff utilization, a wealth of products and systems are becoming attractive options in the delivery of highway projects. The TRB National Cooperative Highway Research Program's NCHR...
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NCHRP Synthesis 593
August 10, 2022
State departments of transportation (DOTs) have been investing in 3D modeling and sharing 3D digital models with contractors. Some DOTs have piloted the use of 3D digital models as contract documents, others continue to provide contractors with 3D digital models for information purposes, and some have not begun using 3D digital models in construction. The TRB National Cooperative Highway Research ...
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NCHRP Synthesis 592
July 22, 2022
The Highway Safety Improvement Program (HSIP) is a core federal-aid highway program with the purpose of achieving significant reductions in fatalities and serious injuries on all public roads. Although there are federal requirements that guide state HSIP efforts, there are several variations in how state departments of transportation (DOTs) identify, prioritize, and evaluate HSIP projects. The TRB...
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NCHRP Synthesis 591
July 29, 2022
Safety and health programs are vital to the success of state departments of transportation (DOTs). While the safety of all DOT employees is paramount, maintenance and other field workers are exposed to unique hazards that demand a higher level of management than traditional office-based positions. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 591: Use of Safety Management...
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NCHRP Synthesis 590
July 22, 2022
For years, state departments of transportation (DOTs) were solely responsible for quality control (QC) and performed testing and inspection to verify construction quality. However, since the 1970s, many state DOTs have transferred the responsibility for QC processes of their highway-construction projects to contractors. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 590: A...
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NCHRP Synthesis 589
September 01, 2022
Automated collection of pavement data allows agencies to collect data on pavement health, including cracking, rutting, faulting, and roughness, at highway speeds. This provides important information for better pavement decision-making. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 589: Automated Data Collection and Quality Management for Pavement Condition Reporting docum...
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NCHRP Synthesis 588
June 29, 2022
While there are no national standards for rock slope design and rockfall management, many state departments of transportation (DOTs) have developed their own design goals and objectives. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 588: Design Practices for Rock Slopes and Rockfall Management documents DOT practices for the design of rock slopes and rockfall mitigation s...
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NCHRP Synthesis 587
June 30, 2022
To make work zones safer, state departments of transportation (DOTs) use smart technologies with specialized components, such as sensors, communications, software, and electronic equipment, to manage traffic and operations and disseminate traveler information. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 587: Use of Smart Work Zone Technologies for Improving Work Zone Sa...
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NCHRP Synthesis 586
June 01, 2022
Although the use of recycled asphalt materials (RAM) in new asphalt mixtures can reduce the amount of virgin and nonrenewable materials required and increase the rutting resistance of pavements, it may also compromise cracking resistance. To mitigate this issue, asphalt mixtures containing RAM may require the use of a softer binder or recycling agent (RA). The TRB National Cooperative Highway Rese...
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NCHRP Synthesis 585
September 09, 2022
Initial efforts to define and collect bridge element data in the United States started in the late 1990s with the development and implementation of bridge management systems (BMSs). Over the years, the bridge management community provided feedback and made suggestions to improve the bridge element inspection methodology. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 585: ...
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NCHRP Synthesis 584
July 13, 2022
Visualizations are tools for analyzing, reporting, and communicating the complexities of a transportation system and for synthesizing these intricacies into presentations that can be easily understood. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 584: Visualization of Highway Performance Measures documents current practices and methods used by state departments of transp...
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NCHRP Synthesis 583
May 18, 2022
While it is recognized to be in the public interest to permit the installation of utility infrastructure in roadway rights-of-way, the practice has contributed to utility-related issues being one of the leading causes of delays for transportation projects. Subsurface utility engineering (SUE) is an approach state departments of transportation (DOTs) have implemented to locate utilities and assist ...
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NCHRP Synthesis 582
May 20, 2022
Historically, state departments of transportation (DOTs) have employed on-site workforces to execute infrastructure inspection using traditional inspection methods. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 582: Highway Infrastructure Inspection Practices for the Digital Age documents the various technologies - such as unmanned aircraft systems (UASs), embedded and re...
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NCHRP Synthesis 581
May 16, 2022
Departments of transportation (DOTs) are increasing employment of asset management strategies in response to federal and state initiatives. Low-cost and effective treatments applied throughout the life of the asset can be employed prior to significant asset degradation, which otherwise would likely require a high-cost reactionary treatment. The TRB National Cooperative Highway Research Program's N...
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NCHRP Synthesis 580
April 14, 2022
Rough bridge surfaces can increase user costs by accumulative wear and tear on vehicles, increase freight costs resulting from damage to goods or packaging, add to potential safety concerns with nonuniform tire loads, decrease the life of a structure by increasing dynamic loads, and reduce user satisfaction. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 580: Practices for...
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NCHRP Synthesis 579
April 22, 2022
Subsurface drainage is known to pavement professionals to be an important factor affecting pavement performance and preservation of public investment, and numerous studies have emphasized its importance. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 579: Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance documents the current state of practice...
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NCHRP Synthesis 578
March 24, 2022
In the last decade, new technologies have transformed all stages of highway construction as more industry stakeholders have begun incorporating new technologies into their daily construction activities. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 578: Use of Unmanned Aerial Systems for Highway Construction documents the use of Unmanned Aircraft Systems (UAS) by state de...
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