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. 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 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.

Asset Management Approaches to Identifying and Evaluating Assets Damaged Due to Emergency Events 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...

Estimating and Contracting Rock Slope Scaling Adjacent to Highways 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...

Practices for Fabricating Asphalt Specimens for Performance Testing in Laboratories 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 ...

Highway Hydraulic Engineering State of Practice 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...

Alternative Intersection Design and Selection 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...

Incorporating Roadway Access Management into Local Ordinances 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...

Development and Use of As-Built Plans by State Departments of Transportation 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...

Advancements in Use of Geophysical Methods for Transportation Projects 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...

Use of Weigh-in-Motion Data for Pavement, Bridge, Weight Enforcement, and Freight Logistics Applications 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...

Electronic Ticketing of Materials for Construction Management 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...

Concrete Technology for Transportation Applications 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...

Transportation Workforce Planning and Development Strategies 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...

Prioritization of Freight Investment Projects 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...

Leveraging Private Capital for Infrastructure Renewal NCHRP Synthesis 540 September 03, 2019 Public–private partnerships (P3s) can provide solutions to the project delivery challenges faced by state departments of transportation (DOTs) and local transportation agencies in delivering surface transportation infrastructure by aligning risks and rewards between public and private sectors, accelerating project delivery, improving operations and asset management, realizing construction and oper...

Landscape Development and Management Practices for Urban Freeway Roadsides NCHRP Synthesis 539 August 09, 2019 Current practices used by state departments of transporttion to design and manage the urban freeway roadsides (UFRs) environment is the focus of National Cooperative Highway Research Program (NCHRP) Synthesis 539: Landscape Development and Management Practices for Urban Freeway Roadsides. The urban freeway roadsides (UFRs) for this synthesis are those roadsides associated with high visibility urba...

Practices for Online Public Involvement NCHRP Synthesis 538 July 09, 2019 TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 538: Practices for Online Public Involvement summarizes current practices regarding online public participation strategies being used by state departments of transportation (DOTs), as well as explores the effectiveness of using these strategies and tools. Online public participation methods offer agencies the potential for expan...

Impact of Asphalt Thickness on Pavement Quality NCHRP Synthesis 537 July 02, 2019 TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 537: Impact of Asphalt Thickness on Pavement Quality documents transportation agency policy for lift thickness and minimum compaction requirements on resultant asphalt pavement quality. To achieve expected pavement performance, it is important that asphalt concrete (AC) have adequate density. A critical factor in achieving this ...

Bridge Demolition Practices NCHRP Synthesis 536 May 31, 2019 TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 536: Bridge Demolition Practices documents practices used by bridge owners to manage and administer bridge demolition in construction projects. Each year hundreds of bridges are rebuilt or are entirely replaced as part of highway construction projects. Bridge reconstruction or replacement work often entails demolition of part or...

Pedestrian Safety Relative to Traffic-Speed Management NCHRP Synthesis 535 October 30, 2019 Measures that are effective at reducing speed, such as speed humps and mini traffic circles, are sometimes used in low-speed areas such as school zones. But they are often not recommended or allowed (via local policy) on the higher-speed streets typically associated with the highest injury severity for pedestrians. For those higher-speed streets, redesigning them to communicate lower speed, such a...

Emerging Technologies for Construction Delivery NCHRP Synthesis 539 August 07, 2019 The uses and levels of maturity of five advanced technology areas visualization and modeling, interconnected technologies, safety technologies, instrumentation and sensors, and unmanned aircraft systems in transportation highway construction projects are documented in TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 534: Emerging Technologies for Construction Delivery. The syn...

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