Roundabouts have seen unprecedented growth across the United States, from just a handful a decade ago to more than 2,000 and counting. National guidance had to keep pace with the needs of states and communities planning and implementing roundabouts, and NCHRP took a lead role.

TRB’s National Cooperative Highway Research Program (NCHRP) Report 712: Optimization of Tack Coat for HMA Placement presents proposed test methods for measuring the quality and performance characteristics of tack coat in the laboratory and the field, and includes a training manual presenting proposed construction and testing procedures for tack coat materials. Links to appendixes B and D to NCH...

In regions across the nation, bridge engineers know that the next major seismic event is coming—maybe tomorrow, maybe centuries from now. DOTs have the critical charge of designing for earthquakes and protecting the lives of travelers.

On March 5, 2012, TRB’s Long-Term Pavement Performance (LTPP) Committee sent its 29th letter report to Victor Mendez, administrator of the Federal Highway Administration (FHWA), and John Horsley, executive director of the American Association of State Highway and Transportation Officials (AASHTO). The committee's reports are aimed at supporting the further success of the LTPP program, securing ...

TRB’s National Cooperative Highway Research Program (NCHRP) Research Results Digest 370: Guidelines for Project Selection and Materials Sampling, Conditioning, and Testing in WMA Research Studies summarizes a May 2011 workshop designed to help foster cooperation and coordination among warm-mix asphalt (WMA) research studies. The goals of the workshop were to help identify the laboratory and fie...

TRB’s National Cooperative Highway Research Program (NCHRP) Research Results Digest 369: AASHTO T 209: Effect of Agitation Equipment Type on Theoretical Maximum Specific Gravity Values evaluates the effect of using various devices and methods on measured values of theoretical maximum specific gravity (Gmm) used to determine the air void content and the in-place density of hot-mix asphalt (HMA) ...

TRB’s Transportation Research Record: Journal of the Transportation Research Board, No. 2240 consists of 14 papers that explore heat of hydration for cement, moisture transport and deformations in jointed plain concrete pavement, calibrating the mortar flow table, effects of roadway contaminants on titanium dioxide photodegradation of nitrogen oxides, and permeability and mechanical properties ...

TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 423: Long-Term Performance of Polymer Concrete for Bridge Decks addresses a number of topics related to thin polymer overlays (TPOs). Those topics include previous research, specifications, and procedures on TPOs; performance of TPOs based on field applications; the primary factors that influence TPO performance; current cons...

TRB’s Transportation Research Circular E-C160: Polyphosphoric Acid Modification of Asphalt Binders: A Workshop documents the research discussed and presentations made at a April 2009 workshop that explored polyphosphoric acid-modified asphalt and its performance. The circular includes presentations made on a survey on polyphosphoric acid use and issues; the why and how of polyphosphoric acid mo...

TRB’s Transportation Research E-Circular E-C161: Applications of Advanced Models to Understand Behavior and Performance of Asphalt Mixtures is a synopsis of information on the applications of advanced models to understand behavior and performance of asphalt mixtures.

TRB’s National Cooperative Highway Research Program (NCHRP) Report 714: Special Mixture Design Considerations and Methods for Warm-Mix Asphalt: A Supplement to NCHRP Report 673: A Manual for Design of Hot-Mix Asphalt with Commentary presents special mixture design considerations and methods used with warm-mix asphalt. NCHRP Report 714 is a supplement to NCHRP Report 673: A Manual for Design of ...

TRB’s National Cooperative Highway Research Program (NCHRP) Report 709: Investigation of Short-Term Laboratory Aging of Neat and Modified Asphalt Binders provides a proposed method of testing for short-term laboratory aging of neat and modified asphalt binders using the modified German rotating flask as an alternative to the rolling thin film oven test. The following appendixes A-E to NCHRP Rep...

TRB’s Transportation Research Record: Journal of the Transportation Research Board, No. 2253 consists of eight papers that explore time-dependent structural response of full-depth reclamation, the compactability of recycled concrete aggregate, distressed pavements supported on a base course containing recycled concrete aggregate, continuously reinforced concrete pavement containing recycled con...

TRB’s National Cooperative Highway Research Program (NCHRP) Report 704: A Performance-Related Specification for Hot-Mixed Asphalt provides a proposed performance-related specification (PRS) for hot-mix asphalt (HMA) in the form of the Microsoft Windows®-based Quality-Related Specification Software (QRSS). The QRSS is a stand-alone program for Microsoft Windows (versions XP and 7) that employs a...

TRB’s second Strategic Highway Research Program (SHRP 2) Report S2-R26-RR-1: Preservation Approaches for High-Traffic-Volume Roadways documents the state of the practice of preservation treatment on asphalt and concrete pavements on high- and low-volume roadways. The report also report includes general guidelines on the application of preservation treatments on high-volume roadways. The same pr...

TRB’s Transportation Research Record: Journal of the Transportation Research Board, No. 2210 consists of 14 papers that explore permanent deformation, confined dynamic modulus laboratory testing for asphalt concrete, confined dynamic modulus of asphalt mixtures, semirigid asphalt concretes, cracking performance in hot-mix asphalt mix design, and asphalt binders and mixtures containing polyphosp...

TRB’s Transportation Research Record: Journal of the Transportation Research Board, No. 2232 consists of 10 papers that explore management of unsealed gravel roads, assessing potential reactivity of aggregates in presence of potassium acetate deicer, curing conditions on the impact of natural aggregate coatings on concrete performance, polishing tendency of coarse aggregates, resilient modulus ...

TRB’s Transportation Research Record: Journal of the Transportation Research Board, No. 2208 contains 14 papers that explore hot-mix asphalt that contains nickel slag aggregate, rutting resistance of asphalt concrete mixtures that contain recycled asphalt pavement, performance characteristics of thin-lift overlay mixtures, fatigue evaluation of warm-mix asphalt mixtures, and the effect of miner...

TRB’s Transportation Research Record: Journal of the Transportation Research Board, No. 2207 contains 16 papers that explore direct measurements of volatile and semivolatile organic compounds, nano–titanium dioxide additive, performance of Superpave projects, coarse aggregate angularity, physical hardening, new low-temperature performance-grading method, and correlation of moisture loss and str...

TRB’s National Cooperative Highway Research Program (NCHRP) Research Results Digest 364: Validation of LRFD Metal Loss and Service-Life Strength Reduction Factors for Metal-Reinforced Systems summarizes the results of research to further validate some key results of a project that resulted in publication of NCHRP Report 675: LRFD Metal Loss and Service-Life Strength Reduction Factors for Metal-...

TRB’s National Cooperative Highway Research Program (NCHRP) Report 700: A Comparison of AASHTO Bridge Load Rating Methods documents an analysis of 1,500 bridges that represent various material types and configurations using AASHTOWare™ Virtis® to compare the load factor rating to load and resistance factor rating for both moment and shear induced by design vehicles, American Association of Stat...

TRB’s National Cooperative Highway Research Program (NCHRP) Report 696: Performance of Corrugated Pipe Manufactured with Recycled Polyethylene Content provides potential specifications for corrugated drainage pipe manufactured with recycled high-density polyethylene (HDPE). The report includes proposed draft specifications for recycled HDPE, formulations of virgin and recycled HDPE, and drainag...

TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 421: Recycling and Reclamation of Asphalt Pavements Using In-Place Methods discusses the use of hot in-place recycling, cold in-place recycling, and full-depth reclamation of asphalt pavements. In-place recycling and reclamation of asphalt pavements provides agencies with the ability to optimize the value of in-place material...

TRB’s National Cooperative Highway Research Program (NCHRP) Report 702: Precision of the Dynamic Modulus and Flow Number Tests Conducted with the Asphalt Mixture Performance Tester describes the development of precision statements for the dynamic modulus and flow number tests conducted with the Asphalt Mixture Performance Tester.

On August 5, 2011, TRB’s Long-Term Pavement Performance (LTPP) Committee sent its 28th letter report to Victor Mendez, administrator of the Federal Highway Administration (FHWA), and John Horsley, executive director of the American Association of State Highway and Transportation Officials (AASHTO). The committee's reports are aimed at supporting the further success of the LTPP program, securing...

TRB’s Transportation Research Record: Journal of the Transportation Research Board, No. 2209 contains 9 papers that explore shear bond characteristics of tack coats, estimating material-specific moisture damage characteristics of binder-aggregate interface, specifications for aggregate frictional qualities in flexible pavements, design optimization of permeable friction course mixtures, and mac...

TRB’s Transportation Research Record: Journal of the Transportation Research Board, No. 2205 is the third of three volumes that collectively present 90 technical papers pertinent to low-volume roads, 44 by authors from the U.S. and 46 by authors from 18 other countries. Volume 3 contains 31 papers that address materials, and pavement management aspects of low-volume roads.

TRB’s National Cooperative Highway Research Program (NCHRP) 360: Rheological Characterization of Flow Table Reference Material summarizes the key findings of a project that characterized available batches of cement and concrete reference laboratory (CCRL) flow table reference material. The project also explored more efficient, stable, and reproducible methods for future production of the refere...

TRB’s National Cooperative Highway Research Program (NCHRP) Research Results Digest 357: Test Methods and Specification Criteria for Mineral Filler Used in Hot-Mix Asphalt summarizes the key findings of a project that identified test methods for mineral filler that characterize its physical and chemical effects on the performance of mastics and hot-mix asphalt. The project also explored propose...

TRB’s National Cooperative Highway Research Program (NCHRP) RRD 355: Summary of Cast-In-Place Concrete Connections for Precast Deck Systems summarizes the results of a project that developed recommended design and construction specifications and examples for the design and construction of durable cast-in-place reinforced concrete connections for precast deck systems. The project focused on syst...