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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations

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Publication Number:  FHWA-HRT-15-007    Date:  November 2015
Publication Number: FHWA-HRT-15-007
Date: November 2015


Multiple Sources of Safety Information From V2V and V2I: Redundancy, Decision Making, and Trust - Safety Message Design Report

Chapter 1. Introduction


Vehicle-to-vehicle (V2V) communications and vehicle-to-infrastructure (V2I) communications involve the wireless exchange of data among and between infrastructure and vehicles traveling in the same vicinity with the goal of realizing significant safety, mobility, and environmental benefits. This communications capability will enable a host of vehicle- and infrastructure-based safety systems and applications. The vision is that all vehicles on the roadway, (e.g., automobiles, trucks, transit vehicles, and motorcycles), will be able to communicate with other vehicles and the infrastructure to enable active safety applications, as well as improvements in mobility and environmental benefits.The Human Factors for Connected Vehicles (HFCV) research program seeks to understand, assess, plan for, and counteract the effects of signals or system-generated messages that take drivers’ eyes off the road (visual distraction), drivers’ minds off the driving task (cognitive distraction), and drivers’ hands off the steering wheel (manual distraction).

This Federal research investment is a critical factor in developing the knowledge to enable connected vehicle (CV) technologies to save lives and reduce injuries without unintended consequences. The ability to establish the basic principles of attention and distraction within the context of specific advanced communication and messaging technologies (used in vehicles and in roadway infrastructure components) is a challenging effort whose outcomes will form the parameters for and guide consistent development of safer systems and interfaces for countless new applications. When developing new applications, consistency and adherence to basic countermeasures for distraction are paramount to ensuring the ultimate safety of the driver. Human factors research allows the development of more robust algorithms for prioritizing safety and messages that assist the driver, as opposed to providing greater distraction or workload.

From a higher level transportation planning perspective, the National ITS (Intelligent Transportation Systems) Architecture was created to provide a common framework for planning, defining, and integrating ITS. The idea of V2V and V2I communications that enable active safety applications fits into this National ITS Architecture. For example, there are a number of relevant National ITS Architecture Service Packages, including AVSS10-Intersection Collision Avoidance and AVSS05-Intersection Safety Warning[1]. The Intersection Collision Avoidance Service Package describes a system that determines the probability of an intersection collision and provides timely warnings to approaching vehicles so that avoidance actions can be taken. The Intersection Safety Warning Service Package describes a related system that monitors vehicles approaching an intersection and warns drivers when hazardous conditions are detected. Such a system could detect impending violations (e.g., red light violations) and potential conflicts between vehicles occupying or approaching the intersection (e.g., situations where a left turn would be unsafe because of approaching traffic). When a potentially hazardous condition is detected, a warning is communicated to the involved vehicles using short range communications and/or signs/signals in the intersection1.

The scenario described above fits in very closely with the research covered in the current report. In particular, the primary objective of this report is to investigate how drivers handle critical safety information from multiple sources, including V2V and V2I sources. This safety-critical information could include potential conflicts between vehicles occupying or approaching the intersection (e.g., situations where a left turn would be unsafe because of approaching traffic). To meet the objectives of this project, the following specific tasks were completed:

  • Task 1: Literature Review and Gap Analysis.
  • Task 2: Develop Research Plan.
  • Task 3: Execute Research Plan.
  • Task 4: Document Design Guidance.

This report documents the design guidance that comprises task4. The objective of task4 is to integrate the findings from previous project tasks into a safety message design guidance document that can be readily converted into more formal design guidelines by developers of future versions of NCHRP 600: Human Factors Guidelines for Road Systems.

Because this design reference focuses on human factors design issues related to infrastructure and other roadway elements, the current project activities have a similar focus. The target audiences for this information are CV system designers and other State transportation department personnel involved in the development and implementation of V2I applications that provide safety information. Accordingly, the safety messages and design information provided in this report primarily address the V2I component of CV technologies. Also, while V2I communication with drivers can involve both a driver-infrastructure interface (DII) and a driver-vehicle interface (DVI) to provide CV information, this report focuses on providing design guidance related to DIIs, which is the aspect of V2I systems that would be the responsibility of roadway engineers and designers. Table 1 lists the safety message topics and their page locations in this document.

Table 1. DII safety message guideline information.


Page Number

Topic 1. Considerations for Adding a DII to RSE


Topic 2. System-Level Conflicts


Topic 3. Message-Level Incongruence Between DII and DVI Systems


Topic 4. Message Content: Message Elements


Topic 5. Message Content: Use of Symbols and Text


Topic 6. Supporting Driver Trust of Safety Systems


Topic 7. Factors That Affect Gap Choice


Topic 8. Intersection Decision Support for Stop-Controlled Minor and Major Road Junctions


Topic 9. Signalized Left Turn Assist


Topic 10. RLVW


Topic 11. Curve Speed Warning


Topic 12. Road Weather: General Human Factors Considerations


RLVW = Red light violation warning.
RSE = Roadside equipment.

Overview of the Report

The remainder of this report is composed of the following three chapters:

  • Chapter 2. Overview of CV Applications: This section provides the definitions for the key terms used to describe the CV communication architecture, in addition to summary descriptions of the safety applications addressed in this report.

  • Chapter 3. DII Safety Message Guideline Information: This section provides a set of safety message guidance topics for designers to use as a reference—including specific design parameters, identified design problem(s), and/or information—in developing safety applications.

  • Chapter 4. Summary and Conclusions: This section provides a summary of the guideline effort as a whole, and discusses the key project conclusions .



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