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Public Roads - Autumn 2018

Autumn 2018
Issue No:
Vol. 82 No. 3
Publication Number:
Table of Contents

Communication Product Updates

Communication Product Updates

by Lisa A. Shuler of FHWA's Office of Corporate Research, Technology, and Innovation Management

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 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:

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

For more information on R&T communications products available from FHWA, visit FHWA’s Web site at, the FHWA Research Library at (or email, or the National Transportation Library at (or email


State of the Practice for Traveler Information During Nonrecurring Events

Publication Number: FHWA-HRT-17-014


This report identifies and reviews literature and synthesizes the best practices on efforts to understand traveler information needs and related decisionmaking processes within the context of nonrecurring events–planned or unplanned–that impact traffic conditions. Unplanned events may include traffic incidents, severe weather, and other emergencies. Planned events may include road work, sporting events, planned protests, concerts, and holiday celebrations, among others.

This report provides a comprehensive review of current challenges and a look forward at anticipated trends and advances as the landscape of information on nonrecurring events evolves.

The intended audience for this report includes transportation agencies interested in implementing or managing a traveler information system that includes information for nonrecurring events as well as researchers investigating traveler needs and behaviors related to nonrecurring event information.

The document is available at


Summary Report: Cooperative Adaptive Cruise Control Human Factors Study

Publication Number: FHWA-HRT-17-025


This report presents the results of human factors research to examine the effects of cooperative adaptive cruise control (CACC) on driver performance in a variety of situations. CACC is an automated vehicle application that complements the capabilities of the vehicle operator without altering the vehicle operator’s alertness and attention.

CACC combines three driver assist systems: (1) conventional cruise control, which automatically maintains the speed a driver has set, (2) adaptive cruise control, which uses radar or light detection and ranging sensors to automatically maintain a gap the driver has selected between the driver’s vehicle and a 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 in speed and location of other CACC vehicles, even vehicles that the driver cannot see.

FHWA conducted four experiments using a driving simulator as part of this CACC human factors study. The first experiment compared driving with CACC in a string of four or five vehicles with manual control of the following distance. The second experiment examined driver performance when merging into a string of CACC vehicles. The third experiment looked closer at the role of automated braking and auditory alerts in collision avoidance, and the fourth experiment explored the effect of a driver’s preferred following distance on performance and workload.

The research in this report suggests that CACC can reduce driver workload while enhancing safety. However, CACC is only one of many vehicle automation technologies in development or early deployment. The role of the driver will be in flux for many years as known safety and convenience automation technologies advance. Human factors research will need to focus on the ever-changing role of the driver and the resulting effects on the performance of these driver-vehicle systems.

The document is available at


Safety Evaluation of Horizontal Curve Realignment on Rural, Two-Lane Roads

Publication Number: FHWA-HRT-17-066


This evaluation, conducted as part of FHWA’s Evaluation of Low-Cost Safety Improvements Pooled Fund Study, examines the safety effectiveness of horizontal curve realignment by increasing the radius of curved roadway segments on two-lane rural roads. One objective of this strategy is to reduce lane departure crashes, especially run-off-road crashes.

The results of the evaluation showed a substantial and significant reduction in crashes. The economic analysis revealed that increasing the radius of a horizontally curved roadway segment on two-lane, rural roads is a cost-effective safety improvement for reducing all types of crashes.

The researchers determined the crash modification factors associated with curve realignment using the empirical Bayes method and compared the results from existing crash modification factors from cross-sectional studies. This evaluation used data from rural, two-lane roads in California, North Carolina, and Ohio. The evaluation revealed a 68-percent reduction in total crashes, a 74-percent reduction in injury and fatal crashes, a 78-percent reduction in run-off-road and fixed object crashes, a 42-percent reduction in nighttime or reduced-light crashes, and an 80-percent reduction in wet crashes.

This document is intended for safety engineers, highway designers, planners, and practitioners at State and local agencies involved with implementing strategic highway safety plans.

The document is available at


Corrosion Forecasting and Failure Projection of Post-Tension Tendons in Deficient Cementitious Grout

Publication Number: FHWA-HRT-17-074

Bridge tendons can be more susceptible to corrosion than conventional reinforcement with no indication that corrosion is taking place. Failures from deficient grout-induced corrosion have been reported as early as 2 years after construction. FHWA conducted research to provide bridge engineers with a practical methodology for predicting corrosion-induced, post-tensioned tendon failures caused by a grout deficiency or deficiencies.

The goals were twofold: first, to present results from phase two of an experimental study and, second, to develop a methodology to forecast the onset and subsequent rate of wire and strand fractures and tendon failures, given information regarding the extent of grout deficiency or deficiencies.

The study’s results indicate an initiation period for fractures and failures during which corrosion progresses at an increasing rate up to a point, after which the rate of corrosion moderates. The research team investigated other variables including level of prestress, wire strength, number of tendons, tendon length, and fracture and failure rates subsequent to initial occurrence. The report presents equations for bridge engineers to forecast the onset of fractures and failures based on statistics of either localized wire corrosion wastage or grout chloride concentration.

The document is available at


Alternative Contracting Method Performance in U.S. Highway Construction

Publication Number: FHWA-HRT-17-100


This TechBrief presents findings based on empirical data from FHWA’s national study, “Quantification of Cost, Benefits and Risk Associated with Alternative Contracting Methods and Accelerated Performance Specifications.” The study includes documented lessons learned related to two alternative contracting methods: construction manager/general contractor and design-build.

The study collected a first-of-its-kind dataset from 291 completed highway projects. Together, the data form the largest empirical database of project information exclusive to highway construction. The findings provide guidance for State departments of transportation to assist in determining when to use alternative contracting methods to maximize project objectives related to cost, schedule, and intensity performance metrics.

This publication presents the state of the practice in the use of alternative contracting methods and discusses the characteristics of projects for which agencies are using these methods. It also provides information on how alternative methods affect cost certainty, cost growth, project delivery speed, schedule growth, and production rates or project intensity.

The document is available at


Identification of High Pedestrian Crash Locations

Publication Number: FHWA-HRT-17-107

The overall goal of FHWA’s Pedestrian and Bicycle Safety Research Program is to improve safety and mobility for pedestrians and bicyclists. This report documents the research into developing a process to identify locations with high rates of crashes involving pedestrians.

FHWA contacted several cities and States to establish the criteria used to identify and rank locations with high pedestrian crash rates. In all cases, researchers used crash data. In some cases, researchers considered other variables as well, especially when developing the list of sites for treatments. For example, Los Angeles uses a score that considers the age of the pedestrian and a health and equity index in addition to the number of injury crashes and the number of fatal crashes. Several cities create unique lists for intersections, facilities, and areas, recognizing that treatment selection would be different for these element types.

The methods used to identify and evaluate sites with a high crash frequency have evolved in recent decades. For example, the availability of geographic coordinates (latitude and longitude) for crashes has resulted in regular use of geographic information system (GIS) platforms for displaying the locations and density of crashes on maps.

The objective of this FHWA research was to document methods used to identify or prioritize high pedestrian crash sites or areas. Using the information gathered as part of this research, the research team produced the Guidebook on Identification of High Pedestrian Crash Locations (FHWA-HRT-17-106) with best practices and a five-step process to identify locations.

The report is available at The guidebook is available at


Eco-Drive Experiment on Rolling Terrain for Fuel Consumption Optimization (Summary Report)

Publication Number: FHWA-HRT-18-037


This summary report presents a research project sponsored by FHWA’s Office of Operations Research and Development to evaluate the ability of eco-drive, a longitudinal control algorithm, to improve the fuel economy of a vehicle on rolling terrain. The promising results provide justification for the implementation of vehicle-to-infrastructure technology that would appeal to roadway owners, roadway users, and original equipment manufacturers.

Eco-drive is one of many theoretical concepts developed to increase vehicle fuel efficiency and improve the sustainability of the entire transportation system. This study proposes an eco-drive algorithm for optimizing vehicle fuel consumption on rolling terrains, which frequently cause additional fuel waste because of inefficient transformation between kinetic and potential energy.

The study aimed to test and verify the newly developed algorithm on an innovative connected and automated vehicle platform and to quantify the fuel-saving benefits of eco-drive. Researchers compared the proposed eco-drive system to conventional constant-speed cruise control on a total of seven road segments over 47miles (76 kilometers). Experimental data show that up to 20 percent of fuel consumption can be avoided on certain rolling terrains.

This conclusion can enable a rough estimate of fuel-saving potential on given roadways and help State departments of transportation identify roadways where eco-drive could be effectively implemented. The algorithm and experiment can also support original equipment manufacturers in developing and marketing this technology to reduce fuel consumption and emissions in the future.

The document is available at