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.

TRB’s National Cooperative Highway Research Program (NCHRP) Web-Only Document 186: The Superpave Mix Design System: Anatomy of a Research Program describes how the original Strategic Highway Research Program (SHRP) effort was conceived, funded, and managed. The report outlines the research and implementation efforts that brought SHRP products into routine use and summarizes some of the key less...

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) Innovations Deserving Exploratory Analysis (IDEA) Final Report for NCHRP-IDEA Project 144: An Acoustic Emission-Based Test to Determine Asphalt Binder and Mixture Embrittlement Temperature describes an acoustic emission-based test method for characterizing the embrittlement temperature of asphalt binders and mixtures.

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. 2225 consists of 18 papers that explore a model of road-user costs, prioritizing network-level maintenance of pavement segments with multiple distresses, axle load power for pavement fatigue cracking, pavement performance models, models for preliminary analysis of flexible pavement serviceability index data,...

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 National Cooperative Highway Research Program (NCHRP) Research Results Digest 365: Sustainable Pavement Maintenance Practices highlights the current practice in sustainable pavement maintenance and preservation. The report is designed to help quantify and understand how pavement maintenance and preservation practices minimize environmental impacts. As part of the development of this repor...

A featured article in the November-December 2011 issue of the TR News Traffic explores the goals, the problems encountered, the solutions, and the results of the long-term pavement performance traffic data collection effort that has generated the largest repository of high-quality traffic data ever collected.

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 Transportation Research Record: Journal of the Transportation Research Board, No. 2235 consists of 12 papers that examine estimating road vulnerability to damage from overweight vehicles, evaluation of public–private partnerships in roadway preservation, developing a corridor-level infrastructure health index, life-cycle cost-based pavement preservation treatment design, pavement preservati...

TRB’s Transportation Research Record: Journal of the Transportation Research Board, No. 2227 consists of 21 papers that explore widened pavement systems, long-term performance of cold in-place recycled pavements in New York state, selection of pavement for highway rehabilitation, the saw and seal method to control reflection cracking in composite pavements, life-cycle environmental analysis, sa...

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. 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 Transportation Research Record: Journal of the Transportation Research Board, No. 2228 consists of 15 papers that explore performance bond benefit–cost analysis; green contracting in highway construction; optimal hedging of commodity price risks in highway contracts; wireless real-time productivity measurement system; a performance attributes matrix for highway rehabilitation projects; ad...

TRB’s Innovations Deserving Exploratory Analysis (IDEA) Report 148: Cleaning Device to Remove Debris and Chemicals for Crack/Joint Sealing explores development of a tool designed to efficiently remove deicing chemical buildup and prepare pavement cracks and joints for sealing.

TRB’s Transportation Research Record: Journal of the Transportation Research Board, No. 2226 includes 16 papers that address calibration, prediction mechanisms, modeling, validation, and implementation issues related to the Mechanistic–Empirical Pavement Design Guide. This issue of the TRR also addresses structural analysis of pervious concrete pavement, the performance evaluation of two-layer ...

TRB’s National Cooperative Highway Research Program (NCHRP) Report 703: Guide for Pavement-Type Selection includes processes for conducting systematic evaluations of pavement alternatives and for making decisions on pavement-type selection. The processes may be used for both agency-based and contractor-based type selections and may be applied to different pavement types and structures.  Fu...

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 Transportation Research Record: Journal of the Transportation Research Board, No. 2212 contains 13 papers that explore acceptance of geomaterials, water jetting to mitigate defects in drilled shafts, pile load test and implementation of load and resistance factor design specifications, lateral resistance of short rock sockets in weak rock, and field testing of a batter pile group foundati...

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.