There are approximately 1,000 movable highway bridges in the U.S. inventory. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 314: Updating the AASHTO LRFD Movable Highway Bridge Design Specifications allows bridge owners the option of employing site-specific conditions to develop the design wind speed and provides other general updates to previous research from 2000...

Designing extended sections of highway based on the design speed process is relatively straightforward. However, when applied to interchange ramps where high-speed facilities meet low-speed facilities and drivers are expected to accelerate or decelerate over short distances, application of the design speed process is more complex. The TRB National Cooperative Highway Research Program's NCHRP Web-O...

Selection of a design speed should be based upon the anticipated operating speed, topography, adjacent land use, modal mix, and functional classification of the roadway. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 313: Selecting Ramp Design Speeds, Volume 1: Guide provides further detail for selecting an appropriate ramp design speed than presented in the 2018 G...

Project-level Programmatic Agreements (PAs) streamline and expedite the environmental review process and provide departments of transportation with greater flexibility in decision making regarding adverse effects to historic properties and defining appropriate mitigation. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 311: Improving the Efficiency and Consistency o...

In 1999, the Federal Communications Commission (FCC) allocated the intelligent transportation system (ITS) band, also known as the “5.9 GHz band,” for transportation purposes including connected and automated vehicle (CAV) technologies. These technologies enable a host of applications for vehicle‐to-vehicle, vehicle‐to‐infrastructure, and vehicle‐to‐pedestrian communication — collectively known as...

Part-time shoulder use is a congestion relief strategy that allows use of the left or right shoulders as travel lanes during some, but not all, hours of the day. The TRB National Cooperative Highway Research Program's  NCHRP Web-Only Document 309: Safety Performance of Part-Time Shoulder Use on Freeways, Volume 2: Conduct of Research Report  describes the development of crash prediction ...

Left or right shoulders can be strategically opened as travel lanes, and "part-time shoulder use" is defined as using a shoulder "some, but not all, hours of the day.” The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 309: Safety Performance of Part-Time Shoulder Use on Freeways, Volume 1: Informational Guide and Safety Evaluation Guidelines provides an overview of pa...

Since bridges cross over large spans of space they often cross significant features such as busy transportation corridors. In addition, bridges carry heavy vehicles sometimes with dangerous cargos, such as fuel and hazardous chemicals. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 307: Recommended Guidelines for the Selection of Test Levels 2 Through 5 Bridge Rail...

Prior to this research project, state highway agencies did not have tools for reflecting safety in their decisions concerning freeway and interchange projects. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 306: Safety Prediction Methodology and Analysis Tool for Freeways and Interchanges documents a safety prediction method for freeways that is suitable for incorp...

Porous Friction Course (PFC) mixtures are designed with an open aggregate structure to yield high inplace air voids (i.e., typically between 15 and 20 percent). This allows rainwater to drain horizontally through the layer toward the edge of the pavement structure, thereby improving pavement surface friction. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 305: Vali...

Guardrails are an important feature of the roadside that are used to shield errant motorists from becoming involved in even more catastrophic crashes by redirecting vehicles away from fixed hazards such as trees and poles and terrain hazards such as steep roadside slopes and fill embankments. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 304: Criteria for Restorat...

The Moving Ahead for Progress in the 21st Century Act (MAP-21) requires a set of performance metrics to include assessment of serious injuries in crashes. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 302: Development of a Comprehensive Approach for Serious Traffic Crash Injury Measurement and Reporting Systems presents a roadmap for states to develop comprehensiv...

Hydroplaning is a serious problem that is associated with a relatively small but significant number of crashes. Statistics from various parts of the world indicate that approximately 15% to 20% of all road traffic crashes occur in wet weather conditions. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 300: Guidance to Predict and Mitigate Dynamic Hydroplaning on Roa...

Several controlled laboratory studies have shown that air voids (AV) can have a large effect on the performance of asphalt pavements. AVs that are either too high or too low can cause a reduction in pavement life. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 299: Investigating the Relationship of As-Constructed Asphalt Pavement Air Voids to Pavement Performance d...

The first edition of the Highway Safety Manual  (HSM), in 2010, included Safety Performance Functions (SPFs) for roadway segments and intersections. However, not all intersection types are covered in the first edition of the HSM. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 297: Intersection Crash Prediction Methods for the Highway Safety Manual develops SPF...

Run-off-road traffic crashes account for almost one-third of the deaths and serious injuries each year on U.S. highways. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 296: Guidelines for Cost-Effective Safety Treatments of Roadside Ditches provides new proposed design guidance for the configuration of ditches adjacent to the roadway. A supplemental PowerPoint Summ...

The release of the Highway Safety Manual (HSM) by the American Association of State Highway and Transportation Officials (AASHTO) in 2010 was a landmark event in the practice of road safety analysis. Before it, the United States had no central repository for information about quantitative road safety analysis methodology. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Docum...

A workshop, "Revised Contraction Scour Analysis," is presented in this training manual. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 294: Revised Clear-Water and Live-Bed Contraction Scour Analysis Training Manual adheres to the guidance promulgated by the National Highway Institute and the International Association of Continuing Education and Training for adult ...

Over the past 15 years, the nation’s transportation systems have experienced numerous significant disruptions that have resulted in economic loss and loss of human life. The 2020 COVID-19 pandemic is a recent example of how unexpected events can affect the performance and role of transportation systems. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 293: Deploying ...

Highway agencies can use a method to assess roadside hardware and establish priorities on how upgrades of hardware should occur for individual projects or establish policy guidelines on roadside hardware assessments. The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 292: Roadside Hardware Replacement Analysis: User Guide presents how to implement and plan for assessin...