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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Public Roads - July/August 2017

July/August 2017
Issue No:
Vol. 81 No. 1
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 on Data Access, Sharing, and Integration (Report)

Publication Number: FHWA-HRT-15-072  


Transportation planning and investment decisions rely on an accurate and thorough understanding of system performance, which requires integrating data from multiple sources. FHWA initiated the Virtual Data Access Framework to establish a prototype for State and local transportation agencies to share data on planning and operations from multiple sources within a region. The framework brings together many types of transportation data to give planners and operators a multifaceted view of transportation performance both over time and by location. 

This state-of-the-practice review aims to lay both the technical and institutional foundation for all aspects of the framework. The review focuses on current data-sharing and integration practices among State and local agencies and provides examples of data environments, technical integration formats, and business rules for integration and sharing. Researchers investigated and documented best practices, applicability to the data-sharing framework, and incorporation of functional requirements for existing systems. They also examined success factors and data gaps.

This review, which will help in selecting the proposed pilot areas for the proof-of-concept tests of the Virtual Data Access Framework, also establishes a basis from previous experiences that FHWA and its partners will use in defining how the framework is designed in terms of data integration and sharing.

This document is available to download at


Cooperative Adaptive Cruise Control Human Factors Study: Experiment 1—Workload, Distraction, Arousal, and Trust (Report)

Publication Number: FHWA-HRT-16-056  


Cooperative adaptive cruise control (CACC) is an automated vehicle application that aims to complement the vehicle operator’s capabilities without degrading alertness or attention. Researchers at FHWA recently set out to answer a series of questions related to use of this technology. 

Can CACC reduce the driver’s workload relative to manual gap control (that is, maintaining the distance between a vehicle and the one in front of it)? Can CACC increase the probability of driver distraction relative to manual gap control? Can CACC result in reduced driver arousal relative to manual gap control? Does CACC increase the driver’s ability to avoid a crash when exposed to an extreme braking event? And, do drivers trust the CACC system?

This report presents experimental results of a human factors examination of the effects of CACC on driver performance in a variety of situations. Researchers conducted the experiment using a driving simulator, placing subject drivers into scenarios in which they were embedded in platoons of CACC-equipped vehicles. 

A total of 49 licensed drivers were tested in FHWA’s Highway Driving Simulator, with 12 or 13 participants in each of 4 groups. All of the groups drove in the third position in a five-vehicle platoon in which all of the other vehicles were equipped with simulated CACC. The groups differed as to whether the participant vehicle was equipped with CACC and the type of event at the end of the drive that disturbed the longitudinal spacing of the platoon. 

As assessed by the National Aeronautics and Space Administration Task Load Index, the CACC system did reduce perceived driver workload relative to driving without cruise control. CACC users appeared slightly more likely to engage in diversionary activities (for example, listening to the car radio) than control group drivers. CACC yielded a substantial and statistically reliable reduction in the probability of a crash. No evidence suggested that use of CACC leads to lower levels of driver arousal than manual gap control. Further, the study revealed that participants showed a great deal of trust in the CACC system.

This document is available to download at


Intersection Conflict Warning System Human Factors: Final Report (Report)

Publication Number: FHWA-HRT-16-061


Intersection conflict warning systems alert drivers on the through road of the presence of traffic at stop-controlled cross streets. The systems also warn drivers at stop-controlled approaches of the presence of traffic on the through lanes. Studies have shown these warning signs to reduce crashes at rural two-way stop-controlled intersections. However, no standard exists for the wording of warning messages or for the placement of these signs on the stop-controlled approaches. 

FHWA performed this study to provide empirical evidence to support standardization of messaging and sign placement for conflict warnings at intersections. Researchers obtained data from 189 licensed drivers in a four-part laboratory study. In part one, participants viewed video animations of approaches with warning signs, and researchers assessed their comprehension of the signs. In part two, participants indicated their level of agreement with 21 statements concerning various aspects of the warning messages. Researchers used these ratings to assess participants’ mental model for processing the conflict warning messaging. Researchers also identified three dimensions of this model. From most to least influential, these dimensions were comprehension, safety, and affinity or likeability. 

In part three, participants rated the wording of messaging alternatives. Part four explored how comprehension varied between the time when the warning beacons were active and inactive, when the “WHEN FLASHING” placard was present or absent, and whether blankout signs improved comprehension over static signs. 

This document is available to download at