Below are brief descriptions of communications products recently developed by the Federal Highway Administration’s Office of Research, Development, and Technology. All of the reports are or will soon be available from the National Technical Information Service (NTIS). In some cases, limited copies of the communications products are available from FHWA’s Research and Technology (R&T) Product Distribution Center (PDC).

When ordering from NTIS, include the NTIS publication number (PB number) and the publication title. You also may visit the NTIS Web site at www.ntis.gov to order publications online. Call NTIS for current prices. For customers outside the United States, Canada, and Mexico, the cost is usually double the listed price. Address requests to:

National Technical Information Service
5301 Shawnee Road
Alexandria, VA 22312
Telephone: 703–605–6050
Toll-free number: 1–888–584–8332 
Web site: www.ntis.gov
Email: customerservice@ntis.gov

Requests for items available from the R&T Product Distribution Center should be addressed to:

R&T Product Distribution Center
Szanca Solutions/FHWA PDC
700 North 3rd Avenue
Altoona, PA 16601
Telephone: 814–239–1160
Fax: 814–239–2156
Email: report.center@dot.gov 

For more information on R&T communications products available from FHWA, visit FHWA’s Web site at www.fhwa.dot.gov, the FHWA Research Library at www.fhwa.dot.gov/research/library (or email fhwalibrary@dot.gov), or the National Transportation Library at ntl.bts.gov (or email library@dot.gov).

Analytical Method to Measure Water in Asphalt and Its Application to Emulsion Residue Recovery (TechBrief)

Publication Number: FHWA-HRT-15-056

This technical brief presents researchers’ observations that excess water in asphalt binders and pavement mixes can have a deleterious effect on pavement performance. The addition of water to binders through using warm and cold mix technologies highlights the need for accurately measuring water in asphalt. Also, increased water content of biologically derived binders and oils may be responsible for compatibility issues with petroleum-based products.

The document discusses how researchers developed a Karl Fischer titration method for quantifying water in asphalt and asphalt emulsions that is accurate, quick, and highly sensitive. The method’s detection limit is approximately 100 parts per million (ppm). Researchers tested Strategic Highway Research Program binders to assess the effectiveness of the method, applying the method in the evaluation of three emulsion recovery procedures.

Binder films and emulsion residue films treated in a 100-percent humidity environment at 60 degrees Celsius (140 degrees Fahrenheit) showed a maximum of 1,500 ppm water and generally contained approximately 200 ppm more water than nonhumidity-treated films. Using the Karl Fischer titration method, researchers evaluated the method of quantifying water in emulsion residues by heating the residues at 135 degrees Celsius (275 degrees Fahrenheit) until constant mass is obtained–meaning the liquid material has evaporated–and calculating water content by mass loss after evaporation. They found that some residues may contain volatile material other than water that is evaporated at 135 degrees Celsius (275 degrees Fahrenheit), yielding artificially elevated and inaccurate water content measurements by the mass loss method.

This document is available to download at www.fhwa.dot.gov/publications/research/infrastructure/pavements/15056/index.cfm.

Leveraging the Second Strategic Highway Research Program Naturalistic Driving Study: Examining Driver Behavior When Entering Rural High-Speed Intersections (Report)

Publication Number: FHWA-HRT-17-016

Intersections, particularly stop-controlled intersections in rural areas, are the locations of a significant number of traffic crashes. Factors that contribute to these crashes include inadequate surveillance, failure to obey/yield, driver inattention, and speed.

This research study examines stopping and scanning behavior as drivers approached and entered rural high-speed intersections, producing actionable insights into transportation safety by leveraging the second Strategic Highway Research Program (SHRP2) safety databases.

Researchers found that brake distance was sufficiently predicted by brake speed (the speed at which the driver was moving upon initial brake activation). Researchers determined that the probability of making a complete stop varied significantly with average annual mileage and expressed risk associated with performing rolling stops. Participants with higher average annual mileage were more likely to make complete stops.

The research team divided intersection approaches into five segments, and analyzed total glance duration in eight regions of interest within each segment. Researchers found a noteworthy difference among intersection crossings according to the type of stop performed. Drivers who came to a complete stop spent just 39.2 percent of their prestop time scanning the intersection, while rolling stoppers spent 74.5 percent. This suggests that complete stoppers focus on getting to the intersection and then stop, scan, and proceed, whereas rolling stoppers scan the intersection prior to arrival so that they can proceed at higher speeds while maintaining a perception of safety.

This report details the SHRP2 data acquisition process, exploratory analysis, and results. It is available to download at www.fhwa.dot.gov/publications/research/safety/17016/index.cfm.

Cooperative Adaptive Cruise Control Human Factors Study: Experiment 4–Preferred Following Distance and Performance in an Emergency Event (Report)

Publication Number: FHWA-HRT-17-024

This report describes the fourth and final experiment in a series of four studies that explore cooperative adaptive cruise control (CACC), which combines three driver assist systems: (1) conventional cruise control, which automatically maintains the speed a driver has set; (2) adaptive cruise control, which uses sensors to automatically maintain a gap the driver has selected between the driver’s vehicle and a slower-moving vehicle ahead; and (3) dedicated short-range communications to transmit and receive data with surrounding vehicles so that the cruise control system can more quickly respond to changes and speed and location of other CACC vehicles (including vehicles that the driver cannot see).

When using CACC, drivers share vehicle control with an automated system that includes vehicle-to-vehicle and vehicle-to-infrastructure communications. Communications between nearby CACC-equipped vehicles will enable automated coordination and adjustment of longitudinal control through throttle and brake activations. Automated control should enable CACC-equipped vehicles to safely travel with smaller gaps between vehicles than drivers could safely manage on their own. Smaller gaps should subsequently increase the roadway capacity without increasing the physical amount of roadway. However, shorter following gaps lead to problematic human factors issues.

This report presents human factors research to examine the effects of CACC on driver performance in a variety of situations. The findings support the idea that performance depends more on overall CACC following distance settings than with drivers’ personal preferences. This will enable CACC systems to implement a single following distance gap (or set of gaps based on vehicle physics). The results show that it is critical that drivers receive clear alerts when it is necessary to take over control of the vehicle. Without such measures, it is possible that CACC implementation may not result in improved roadway safety.

This report is available to download at www.fhwa.dot.gov/publications/research/safety/17024/index.cfm.

FHWA Research and Technology Evaluation: Gusset Plates Final Report (Report)

Publication Number: FHWA-HRT-17-039

After the I–35W Mississippi River Bridge in Minneapolis, MN, collapsed in 2007, the National Transportation Safety Board (NTSB) issued recommendations to FHWA and the American Association of State Highway and Transportation Officials (AASHTO) to prevent similar catastrophic bridge failures. An FHWA research project to assess the performance and design of steel gusset plate connections facilitated actions that addressed one of the final NTSBrecommendations.

As part of the FHWA research and technology program evaluation, FHWA decided to evaluate the gusset plate project to better understand how FHWA’s investment in gusset plate research has affected the design and rating of gusset plates. This report documents the findings of a summative evaluation of the project. The report focuses on outcomes resulting from collaboration between FHWA and NTSB. Data collection for the evaluation relied primarily on telephone interviews with stakeholders, as well as document searches and reviews.

This evaluation focused on processes FHWA used to develop the National Cooperative Highway Research Program Project 12-84 following the I–35W bridge collapse. Strong relationships and a commitment to safety among FHWA, NTSB, and AASHTO are apparent in the timeline leading up to the publication of the final report and in discussions the evaluation team held with stakeholders.

The evaluation team determined that FHWA provided vital support to NTSB to determine the cause of the bridge collapse, assisted NTSB’s process for choosing a final safety recommendation, expedited research underlying the publication of results, and informed updates to AASHTO specifications. The gusset plate project provided essential knowledge that led to the rapid development of national safety standards that will help prevent other potential gusset plate bridge design failures.

This report is available to download at www.fhwa.dot.gov/publications/research/randt/evaluations/17039/index.cfm.