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Notice and Request for Information and Comment on Development and Application of Crash Warning Interface Metrics

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National Highway Traffic Safety Administration (NHTSA), DOT.


Notice and request for information and comment on development and application of crash warning interface metrics.


During the NHTSA-led Human Factors Forum on Advanced Vehicle Safety Technologies in early 2007, participants from the automobile industry, government, and academia gathered to discuss the research necessary to ensure that future design and operation of these technologies are developed with an understanding of the driver's ability to use them. Underlying this objective is a requirement to have techniques and metrics to quantify how well drivers can use and benefit from the technologies. Without common, reliable, and safety-related metrics, it is difficult to develop, evaluate, and compare different systems as well as to determine the impact of non-standardized warning interfaces.

To address this issue, NHTSA is initiating a program to develop a set of standard metrics and test procedures to assess the Driver-Vehicle Interface (DVI) of Advanced Crash Warning Systems (ACWS). ACWS are technologies to assist drivers who may be unaware of impending collisions by alerting them of potential threats. Examples include forward collision warnings, lane departure warnings, and road departure warnings. The DVI is the means by which ACWS communicate with drivers to help them avoid a threat. In order for ACWS to achieve their intended safety benefits, drivers need to be able to quickly understand the ACWS threat information and respond appropriately without confusion. The warning timing, reliability, warning modes, device controls, and displays are examples of the DVI characteristics that can affect the ability of drivers to achieve the intended safety benefits without possible adverse consequences. Crash Warning Interface Metrics (CWIM) are derived from tests of drivers' performance using ACWS, indicating the compatibility of the DVI with drivers' capabilities and needs.

This notice invites comments, suggestions, and recommendations from all individuals and organizations that have an interest in the development and use of Crash Warning Interface Metrics. NHTSA requests comments to assist the agency in identifying, evaluating, and selecting CWIM and associated test methods for assessing the role of the DVI in influencing driver performance with ACWS.


You should submit your comments early enough to ensure that Docket Management receives them not later than April 17, 2008. Late comments may be considered.


You may submit comments identified by DOT Docket ID Number NHTSA-2007-0038 by any of the following methods: Start Printed Page 11460

  • Federal eRulemaking Portal: Go to Follow the online instructions for submitting comments.
  • Fax: 202-493-2251.
  • Mail: Docket Management Facility, M-30, U.S. Department of Transportation, West Building, Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.
  • Hand Delivery or Courier: West Building, Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC, between 9 a.m. and 5 p.m., Eastern Time, Monday through Friday, except Federal holidays.

Instructions: For detailed instructions on submitting comments and additional information on the rulemaking process, see the Public Participation heading in the SUPPLEMENTARY INFORMATION section of this document.

Note that all comments received will be posted without change to, including any personal information provided. Please see the Privacy Act heading below.

Privacy Act: Anyone is able to search the electronic form of all comments received into any of our dockets by the name of the individual submitting the comment (or signing the comment, if submitted on behalf of an association, business, labor union, etc.). You may review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78).

Docket: For access to the docket to read background documents or comments received, go to at any time or to West Building, Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC, between 9 a.m. and 5 p.m., Eastern Time, Monday through Friday, except Federal holidays.

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Eric Traube, Office of Human Vehicle Performance Research, National Highway Traffic Safety Administration, 1200 New Jersey Avenue, SE., Washington, DC 20590. Telephone number: 202-366-5673; E-mail

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One recent development in vehicle safety technology has been the introduction of Advanced Crash Warning Systems (ACWS). These systems alert drivers about emerging hazardous situations using auditory, visual, or haptic warnings. In some cases, limited vehicle control action, such as braking or steering, are initiated to alert drivers to respond. Systems that do not warn or provide some type of feedback to the driver would not be considered ACWS. Examples of ACWS include (but are not limited to) road departure warnings, lane change (blind spot) warnings, adaptive cruise control, curve speed warnings, and forward collision warnings.

While the implementation of ACWS in production vehicles appears to be increasing, the question remains as to whether ACWS will produce significant safety improvements or will introduce unforeseen problems, particularly if drivers are unfamiliar with ACWS warnings. The NHTSA-sponsored Human Factors Forum on Advanced Vehicle Safety Technologies was held in 2007 to begin to address this issue.

A key to ACWS effectiveness is the quality of its interface, which can affect the driver's performance as well as acceptance of the technology. The interface of an ACWS consists of the controls that drivers use to adjust the system operation and any visual, auditory, or haptic warnings as well as operational cues that can influence driver actions. Whether drivers will be able to effectively utilize this feedback to avoid crashes may be determined through tests that measure various aspects of driver/vehicle response, such as brake reaction time, gas pedal release time, brake force, threat recognition, response appropriateness, eye glance behaviors, etc. Because different manufacturers employ different test protocols, measures, and criteria to determine the design of the Driver-Vehicle Interface (DVI), a variety of interfaces have been proposed and in some cases deployed in production vehicles.

The Forum's focus on driver centered design highlighted the importance of these issues. Attendees stressed that future research should determine how to assess if drivers understand the system, if the system leads to appropriate driver reactions, and if drivers accept the new systems. Other discussion focused on the unintended consequences—understanding how inadequate mental models may affect safety and how design can strengthen those models. In addition, discussion addressed research needs related to integration of interfaces when several warning systems are installed. Other topics included the question of designing interfaces compatible with the capabilities of the majority of the driving population and compatible with each other. The later is where the topic of interface standardization was addressed as an approach to minimize driver confusion.

Without a meaningful basis for evaluating the driver/vehicle interface, the research topics suggested at the Forum would be difficult to resolve. In order to better evaluate and compare different ACWS interfaces, NHTSA has initiated a major research effort to develop human factors test protocols and related metrics of driver/system performance that will form the basis for a set of crash warning interface metrics (CWIM). The development of CWIM will benefit public safety by helping to identify effective ACWS. Secondly, CWIM will help to assess the whether lack of standardization of ACWS interface characteristics could confuse drivers and compromise system effectiveness. The issues of standardization and CWIM are interrelated because without metrics, the effects of non-standardized DVIs on driver performance cannot be objectively assessed. In addition, NHTSA may use results from the CWIM project to enhance test procedures developed under the Advanced Crash Avoidance Technology program and other ongoing activities.

NHTSA requests comments to assist the agency in identifying, evaluating, and selecting CWIM and associated test methods for assessing the role of the DVI in influencing driver performance with ACWS. The agency is interested in comments related to both the scientific merit of different metrics as well as the practical or institutional considerations for end users of CWIM.

While the research effort is making use of published research, guidelines, standards, and other materials, it will benefit greatly from the experience and opinion of various stakeholder groups, who face related issues. Therefore, we hope to receive comments that will reflect lessons learned, new ideas and approaches, criteria for optimal methods, practical concerns in application, and other information unlikely to be reflected in published literature. Responses to this notice may also help to provide greater consistency with current practice and assure maximum usefulness.

The following are some of the key issues that the agency would like commenters to address. In addition to general comments, the agency requests submission of documents, studies, test protocols, or references relevant to the issues.

A. Potential Measures and Procedures

(A1) What techniques, metrics, and criteria are now being used by vehicle manufacturers for developing and evaluating the human factor aspects of interface design and operation of ACWS at various stages of product development? What tools and environments (e.g. simulators, test Start Printed Page 11461tracks, etc.) are used to evaluate DVIs? Are there “lessons learned” regarding their use, practicality, or acceptance? What measures and procedures are the most predictive of relevant safety parameters?

(A2) To what extent are DVI assessment techniques shared industry-wide and to what extent are these methods proprietary? What performance requirements, standards or guidance documents have been used by vehicle manufacturers and/or system suppliers to address the human factors aspects of the design and evaluation of CWIM for ACWS? Are they helpful? What are their limitations?

(A3) If various functions (e.g., Adaptive Cruise Control (ACC), Frontal Crash Warning (FCW), Lane Departure Warning (LDW)) are packaged together as an integrated in-vehicle system, can CWIM be applied individually to each function or is there a need to treat each function in the context of the other functions present as well as other aspects of vehicle design? How can or should this be done? Are there common metrics and protocols that can be used to assess several ACWS?

B. Evaluation of CWIM

(B1) What criteria should be used to determine the most sensitive, reliable, relevant, and useful metrics?

(B2) If consumers are annoyed or otherwise dislike the system, they may turn it off or not purchase it. How should consumer acceptance or driver annoyance be evaluated with respect to their influence on system effectiveness?

(B3) Driver response to ACWS can vary from person to person. Even the same person can vary in performance depending on their state of mind, e.g., drowsy or distracted. What subsets of the population need to be included in developing criteria for CWIM? How should their needs and capabilities be integrated into the assessment?

(B4) What type of evaluation of the DVI is being done or should be done to follow up on driver performance with production systems and its implication for the validity of CWIM?

C. Applying CWIM

(C1) CWIM may be used by suppliers, vehicle manufacturers, and the Government to design, evaluate, and compare usability and potential safety implications of ACWS. However, protocols that are too complicated or costly may be difficult to implement. Protocols that are perceived as invalid or not sensitive to different characteristics of interface design may not be used. What are the practical considerations that need to be factored into the development of metrics and related test protocols to make them useful and also acceptable to those who must apply the methods? What factors should be considered in the choice of test equipment (e.g., simulators, test tracks, vehicle instrumentation) needed to collect driver data?

(C2) As the number of ACWS increases in the vehicle fleet, the lack of standardization of the DVI among different vehicle makes and models may increase the likelihood of driver confusion in responding to the warning information intended to assist the driver. This lack of standardized design and operation of ACWS may reduce the safety benefits of these technologies. What mechanism (e.g., voluntary standards promulgated by SAE, ISO, or NHTSA or mandatory standards set forth in the FMVSS, etc.) should be used to standardize CWIM? How can standardization be balanced against restricting innovation? What test procedures and metrics can be applied to objectively evaluate the need for standardization? What criteria should be used to judge the need for standardization?

(C3) How should the criteria for acceptability be determined; that is, what determines if a DVI is “good enough”? Also, how should the metrics be calibrated to determine if differences between measured values are of practical significance?

D. Research Needs

(D1) What research or other steps are required to identify CWIM and establish their validity as a basis for assessment?

(D2) What is the best way to encourage and coordinate international harmonized research on CWIM?

Public Participation

A. How do I prepare and submit comments?

Your comments must be written and in English. To ensure that your comments are correctly filed in the Docket, please include the docket number of this document in your comments.

Your primary comments must not be more than 15 pages long. (49 CFR 553.21). However, you may attach additional documents to your primary comments. There is no limit on the length of the attachments.

Please submit two copies of your comments, including the attachments, to Docket Management at the address given above under ADDRESSES.

Comments may also be submitted to the docket electronically on the Federal eRulemaking Portal at Follow the online instructions for submitting comments.

B. How can I be sure my comments were received?

If you wish Docket Management to notify you upon its receipt of your comments, enclose a self-addressed, stamped postcard in the envelope containing your comments. Upon receiving your comments, Docket Management will return the postcard by mail.

C. How do I submit confidential business information?

If you wish to submit any information under a claim of confidentiality, send three copies of your complete submission, including the information you claim to be confidential business information, to the Chief Counsel, National Highway Traffic Safety Administration, 1200 New Jersey Avenue, SE., Washington, DC 20590. Include a cover letter supplying the information specified in our confidential business information regulation (49 CFR part 512).

In addition, send two copies from which you have deleted the claimed confidential business information to Docket Management at the address given above under ADDRESSES, or submit them electronically through the Federal eRulemaking Portal at

D. Will the agency consider late comments?

We will consider all comments that Docket Management receives before the close of business on the comment closing date indicated above under DATES. To the extent possible, we will also consider comments that Docket Management receives after that date.

E. How can I read the comments submitted by other people?

You may read the comments received by the Docket Management at the address given under ADDRESSES. The hours of the Docket are indicated above in the same location. To read the comments on the Internet, go to Follow the online instructions for accessing the docket.

Please note that even after the comment closing date, we will continue to file relevant information on the docket as it becomes available. Further, some people may submit late comments. Accordingly, we recommend that you periodically check the docket for new material.

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Issued on February 26, 2008.

Joseph N. Kanianthra,

Associate Administrator for Vehicle Safety Research.

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[FR Doc. E8-4004 Filed 2-29-08; 8:45 am]