Accurate traffic forecasts for highway planning and design help ensure that public dollars are spent wisely. Forecasts inform discussions about whether, when, how, and where to invest public resources to manage traffic flow, widen and remodel existing facilities, and where to locate, align, and how to size new ones. The TRB National Cooperative Highway Research Program's NCHRP Report 934: Traff...

State transportation agencies will always fulfill a role in the emergency-management effort - for all incidents, from the routine traffic incident through major emergencies to catastrophic events. State agency plans and procedures are expected (indeed required if the agency seeks federal compensation) to be related to state and regional emergency structures and plans. This involves multi-agency...

Since 2009, when NCHRP's last Security 101 report was released, there have been significant advances in transportation security approaches, including new strategies, programs, and ways of doing business that have increased the security of transportation systems as well as ensured their resiliency. Hazards and threats to the system have also continued to evolve since 2009. While the inciden...

Between 2005 and 2011, the number of traffic fatalities in the U.S. declined by 11,031, from 43,510 in 2005 to 32,479 in 2011. This decline amounted to a reduction in traffic-related deaths of 25.4 percent, by far the greatest decline over a comparable period in the last 30 years. Historically, significant drops in traffic fatalities over a short period of time have coincided with economic rece...

More than 90 percent of highways and roads in the United States are built using hot-mix asphalt (HMA) or warm-mix asphalt mixtures, and these mixtures now recycle more than 99 percent of some 76.2 million tons of reclaimed asphalt pavement (RAP) and about 1 million tons of recycled asphalt shingles (RAS). According to the National Asphalt Pavement Association, cost savings in 2017 totaled appro...

Examples of transformational technologies—many are discussed in technical and popular media—include wireless telecommunications, shared vehicles, connected vehicles, fully autonomous vehicles, alternative-fuel vehicles, smart cities and communities, big data analytics, internet-of-things, as well as UAVs or drones, 3-D printing, and more. Public agencies face significant challenges continuing t...

Recent federal legislation has established requirements for agencies to set performance targets and report on safety, pavement, and bridge conditions; transit asset state of good repair; system performance; freight; and mobile source emissions. These requirements have resulted in increased visibility and attention to Transportation Performance Management (TPM) and increased awareness of the imp...

Laboratory conditioning of asphalt mixtures during the mix design process to simulate their short-term aging influences the selection of the optimum asphalt content. In addition, long-term conditioning affects the mixture and binder stiffness, deformation, and strength evaluated with fundamental characterization tests to assess mixture performance. The current standard conditioning procedure, A...

State DOTs are increasingly subject to Total Maximum Daily Load (TMDL) requirements for water quality improvement that are implemented through National Pollutant Discharge Elimination System (NPDES) permits. As a result, state DOTs may incur significant costs to construct, operate, maintain, and monitor performance of best management practices and other stormwater treatment facilities that trea...

Analysis of the erodibility of geomaterials is important for the study of problems related to soil erosion such as bridge scour, embankment overtopping erosion, and stream stability. Erodibility is the relationship between the soil erosion rate and fluid velocity or hydraulic shear stress. Since different soils have different geotechnical properties, their erosion rates vary. The TRB National C...

Pavement smoothness (or roughness) is used by state highway agencies for monitoring network condition and other purposes such as assessing construction quality and optimizing investments in preservation, rehabilitation, and reconstruction. States are also required to report the International Roughness Index (IRI) as an element of the federal Highway Performance Monitoring System (HPMS). Because...

Firms that have graduated from the federal Disadvantaged Business Enterprise (DBE) program or have successfully competed for state transportation agency contracts are the focus in NCHRP Research Report 913: Compendium of Successful Practices, Strategies, and Resources in the U.S. DOT Disadvantaged Business Enterprise Program. The DBE program provides small businesses owned and controlled by soc...

TRB’s National Cooperative Highway Research Program (NCHRP) Research Report 912: Guidelines for Detection and Remediation of Soluble Salt Contamination Prior to Coating Steel Highway Structures consolidates practical guidance on the detection and remediation of soluble salt contamination prior to coating steel highway structures. Soluble salts are those that dissociate in solution into anionic ...

Geometric design practitioners in state transportation agencies have a new set of guidelines on probability of vehicle rollover based on various roadside design features. NCHRP Research Report 911: Guidelines for Traversability of Roadside Slopes will assist practitioners in the reduction of serious injury crashes associated with rollovers on roadside slopes. Data from the National Automotive S...

The distance between the driver’s line of sight along the roadway ahead on a horizontal curve and a sight obstruction on the inside of the curve is known as the horizontal sightline offset (HSO). Highway agencies can use  NCHRP Research Report 910: Design Guidelines for Horizontal Sightline Offsets as guidance to address the types of sight distance restrictions that are most likely to be e...

TRB’s National Cooperative Highway Research Program (NCHRP) Research Report 909: Guide to Truck Activity Data for Emissions Modeling explores methods, procedures, and data sets needed to capture commercial vehicle activity, vehicle characteristics, and operations to assist in estimating and forecasting criteria pollutants, air toxics, and greenhouse gas emissions from goods and services movemen...

TRB’s National Cooperative Highway Research Program (NCHRP) Research Report 908: Acceptance Criteria of Complete Joint Penetration Steel Bridge Welds Evaluated Using Enhanced Ultrasonic Methods presents guidelines for evaluating complete joint penetration (CJP) welds in steel bridges and proposes modifications to the American Association of State Highway and Transportation Officials (AASHTO)/Am...

Carbon fiber reinforced polymer (CFRP) is becoming a recognized alternative to traditional construction materials in a wide range of civil engineering applications. An example of such applications is the use of CFRP cables or bars as prestressing tendons for concrete bridge girders, especially in aggressive environments where steel prestressing strands are susceptible to corrosion. Despite thei...

TRB’s National Cooperative Highway Research Program (NCHRP) Research Report 906 includes proposed revisions to the AASHTO LRFD Bridge Design Specifications minimum flexural reinforcement provisions for load and resistance factor design (LRFD) with detailed design examples illustrating the application of the proposed revisions. According to the AASHTO LRFD Bridge Design Specifications, minimum r...

TRB’s National Cooperative Highway Research Program (NCHRP) Research Report 905: Measuring the Effectiveness of Public Involvement in Transportation Planning and Project Development provides a field-validated and practitioner-ready toolkit to measure the effectiveness of a transportation agency’s public involvement activities. The toolkit is designed to collect feedback from the public on sever...