Asphalt binders experience aging that occurs in two distinct stages under quite different conditions: (1) short-term during construction (plant mixing, storage, placement, and compaction) and (2) long-term during the service life of the pavement. The TRB National Cooperative Highway Research Program's pre-publication of NCHRP Research Report 967: Asphalt Binder Aging Methods to Accurately Reflect Mixture Aging documents research conducted to improve laboratory binder conditioning methods to accurately si...

There is a need to identify new or improved laboratory and field test methods to measure the electrochemical properties of earthen materials surrounding buried or embedded steel elements. The TRB National Cooperative Highway Research Program's NCHRP Research Report 958: Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials presents a protocol for evaluating the corrosion potential of earthen materials in contact with steel highway structures.

Cross-frames are important structural components that serve many functions throughout the service life of steel I-girder bridges. Under repetitive load cycles caused by heavy truck passages, cross-frames and their connections can be susceptible to load-induced fatigue cracking if not properly designed. The TRB National Cooperative Highway Research Program's NCHRP Research Report 962: Proposed Modification to AASHTO Cross-Frame Analysis and Design addresses knowledge gaps in an attempt to improve the reli...

Alternative Intersections and Interchanges (A.I.I.s) are designs that improve operations and safety for motorized traffic by strategically adjusting the geometric features at a given location, working on the general principle of redistributing motor vehicle demand at an intersection in an attempt to limit the need to add capacity with new lanes to improve traffic flow. The TRB National Cooperative Highway Research Program's NCHRP Research Report 948: Guide for Pedestrian and Bicyclist Safety at Alternati...

Laboratory testing and field experience have shown that highway concrete should be properly air entrained to resist the action of freezing and thawing, particularly in wet climates. Several gaps in the state of the knowledge still exist. The TRB National Cooperative Highway Research Program's NCHRP Research Report 961: Entrained Air-Void Systems for Durable Highway Concrete addresses these gaps and, more specifically, investigates innovative test methods for effectively characterizing the air system in f...

The diverging diamond interchange (also known as a double crossover diamond interchange) is a relatively new design to the United States. This design can increase throughput and safety without widening bridge structures. The TRB National Cooperative Highway Research Program's NCHRP Research Report 959: Diverging Diamond Interchange Informational Guide, Second Edition presents a comprehensive guide to the design and operation of diverging diamond interchanges and updates material found in the FHWA’s Dive...

State highway agency equipment fleet assets are vital to the delivery of agency programs, projects, and services. Measuring, monitoring, and reporting on asset utilization levels are necessary for the management of the equipment fleet and meeting the highway agency’s business needs. The TRB National Cooperative Highway Research Program's NCHRP Research Report 957: Utilization Measurement and Management of Fleet Equipment is both a handbook on equipment utilization concepts and a guide for making cost-eff...

Pavement recycling is a technology that can restore the service life of pavement structures and stretch available funding for pavement rehabilitation. In general, pavement recycling techniques remix the existing pavement material and reuse it in the final pavement in the form of a stabilized layer. Limitations to further widespread implementation of pavement recycling processes have been reported in previous national research efforts. The TRB National Cooperative Highway Research Program's  NCHRP Re...

Management of traffic signal systems is a critical function for many transportation agencies. Thanks to advancements in technology, it is now possible to collect large amounts of data at signalized intersections, leading to the development of dozens of performance measures. The TRB National Cooperative Highway Research Program's  NCHRP Research Report 954: Performance-Based Management of Traffic Signals provides information to help agencies invest in signal performance measures as part of a co...

Traditional approaches to safety have focused on identifying high-crash locations and implementing projects to address predominant concerns at these locations. The systemic approach to safety is a method of safety management that typically involves lower unit cost safety improvements that are widely implemented based on high risk factors. The TRB National Cooperative Highway Research Program's NCHRP Research Report 955: Guide for Quantitative Approaches to Systemic Safety Analysis provides guidance to st...