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.

Implementation of Subsurface Utility Engineering for Highway Design and Construction 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 ...

Highway Infrastructure Inspection Practices for the Digital Age 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...

Rehabilitation of Culverts and Buried Storm Drain Pipes 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...

Practices for Ensuring the Smoothness of Concrete Bridge Decks 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...

Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance 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...

Use of Unmanned Aerial Systems for Highway Construction 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...

Collaborative Practices for Performance-Based Asset Management Between State DOTs and MPOs 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...

Practices for Project-Level Analyses for Air Quality 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...

Lighting Practices for Isolated Rural Intersections NCHRP Synthesis 575 January 26, 2022 Roadway lighting is a widely recognized intervention for reducing nighttime crashes and isolated rural intersection lighting appears to be beneficial overall, but predicting the benefits likely at a specific location is very difficult. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 575: Lighting Practices for Isolated Rural Intersections is designed to help provide a found...

Temporary Pavement Markings Placement and Removal Practices in Work Zones 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...

Practices for Integrated Flood Prediction and Response Systems 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...

Night and Weekend Movement of Oversize/Overweight Loads 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...

Load Rating of Bridges and Culverts with Missing or Incomplete As-Built Information NCHRP Synthesis 571 February 11, 2022 Load ratings are used in part to allocate federal funding to agencies and to plan for repairing, replacing, and rehabilitating bridges. Therefore, load ratings can affect the movement of goods throughout a region and are vitally important to the continued safe and efficient operation of the highway system. The TRB National Cooperative Highway Research Program's NCHRP Synthesis 571: Load Rating of ...

Practices for Closing Out Highway Projects from Substantial Completion to Final Payment 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...

Practice and Performance of Cold In-Place Recycling and Cold Central Plant Recycling 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...

Portland Cement Concrete Pavement Joint Sealant Practices and Performance 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...

Summary State DOT Practices for Developing and Implementing TSMO Plans 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...

Practices for Bridge Approach Systems 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...

Maintenance and Surface Preparation Activities Prior to Pavement Preservation Treatments 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...

Practices for Selecting Pedestrian and Bicycle Projects 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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