Measuring Distraction: Methods & Techniques

Papers, polls, Q&A items, and comments on this page are oriented to topics and issues associated with the methods and techniques used to measure driver distraction. Feel free to post comments on issues outlined below, or in response to papers, polls, and/or questions submitted to our expert panel. These discussions are meant to emphasize questions of scientific rigor for research and evaluation efforts. A moderator has been assigned to periodically synthesize comments, keep discussions focused and moving, emphasize key points, and offer additional insights into related issues.

DISCUSSION ISSUES/TOPICS

Methods, Measures & Tools

How can driver distraction be safely and rigorously studied in normal driving? How valid are studies that use test tracks, simulators, or laboratory methods?
What measures (dependent variables) are meaningful indices of driver distraction? How do these relate to roadway safety outcomes?
What technologies (e.g., physiological monitoring), devices (e.g., eye trackers), or analytic techniques (e.g., steering control inputs) can be used to capture measures of distraction?
Are there good models that allow you to predict the distracting effects or crash risks associated with a particular distractor?
What, if any, mechanisms are needed to aid in the investigation of technology related crashes and what tools are needed to support these efforts?

Research Needs

What are the important unanswered questions relating to the scientific measurement of driver distraction? Where should research resources be directed?

Content Available In Each Topic Area

  Paper
  Comment
  Ask the Expert
  Poll

Methods, Measures & Tools
	Association Between Cellular-Telephone Calls and Motor Vehicle Collisions 5/18/00 10:36:46 AM Measuring Driver Visual Distraction with a Peripheral Detection Task 5/18/00 11:12:37 AM A Technical Platform for Driver Inattention Research 5/18/00 1:34:17 PM The Development of a Design Evaluation Tool and Model of Attention Demand 5/18/00 1:34:25 PM Divided Attention Ability of Young and Older Drivers 5/30/00 1:12:17 PM Driver Workload Assessment of Route Guidance System Destination Entry While Driving: A Test Track Study 5/30/00 5:41:52 PM Proposed Driver Workload Metrics and Methods Project 5/31/00 5:09:07 PM Measuring distraction: the Peripheral Detection Task 6/1/00 11:58:18 AM Need a way to track collisions where Cellular is being used. 7/5/00 2:52:06 PM Some states do collect this data 7/6/00 9:03:20 AM 2nd and 3rd degree causes 7/8/00 7:27:54 PM NHTSA data-base 7/9/00 8:23:25 PM Can slow speeds cause accidents? 7/10/00 12:16:31 AM distracting dolphins 7/12/00 11:20:43 AM Cellular Phone Turns 7/12/00 1:36:14 PM Cellular Phone Turns 7/12/00 1:37:15 PM Please Explain (see full question below) 7/14/00 10:06:46 AM Why not use horse blinders 7/18/00 3:49:28 PM Driver responsability 7/18/00 4:30:21 PM Measuring and Taxing the Social Costs of Distracted Drivers 7/18/00 4:32:06 PM Accidents 7/18/00 6:20:24 PM Driver testing 7/18/00 6:27:38 PM Nip it in the Bud 7/18/00 8:16:16 PM Drunk Driving Analogy 7/19/00 8:42:44 AM Promising research direction 7/19/00 11:15:13 AM Cell phones receiving undue criticism 7/19/00 12:04:04 PM Responsible Drivers Need Help! 7/20/00 7:51:11 PM Cellular Phone Turns 7/20/00 11:44:02 PM Punishment to meet the crime 7/20/00 11:54:56 PM Nip it in the ????? 7/21/00 12:11:20 AM Drunk driving analogy II 7/21/00 12:20:41 AM Promises promises 7/21/00 12:26:37 AM Marge needs help! 7/21/00 12:34:59 AM Reasonable assumptions 7/21/00 12:48:35 AM Distractions 7/21/00 11:56:23 PM Daytime Running Lights 7/26/00 7:13:04 AM Moderator Comments and Questions 7/28/00 7:28:28 AM Slow speed or relative speed? 7/30/00 3:59:16 PM Criticism long overdue 7/31/00 2:35:08 AM Primary task of driving 7/31/00 7:49:23 PM In evaluating the safety impacts of in-vehicle technologies, what are appropriate baseline or comparative tasks? 8/1/00 1:05:43 PM What about using specific non-technology tasks as baselines to evaluate safety risks? 8/2/00 3:04:48 PM In your opinion, what is the single most important measure for understanding driver distraction? Why? 8/7/00 8:05:29 AM Barry Kantowitz There are some general principles that apply to the selection of any measure for human factors research. This section is based upon an article in the journal Human Factors (Kantowitz, 1992) that offers a technical discussion of this issue. I have tried to simplify this discussion here. In all science, measurement is the process of assigning numbers to objects in a systematic manner. The scientist interested in measurement must always answer two questions: (representation problem) How is the assignment of numbers to objects justified? (uniqueness problem) To what degree is this assignment unique? Reliability is an index of the consistency of a measure and addresses the representation problem. Validity is an index of the truth of a measure and is related to the uniqueness problem. Good measures are both reliable and valid. Good research must also be generalizable. This means that results can correctly be applied to real-world systems. Generalizability depends upon three factors: subject representativeness, variable representativeness, and setting representativeness (see Kantowitz, 1992 for detailed explanations of these terms.) We can't guarantee that a measure, even if reliable and valid, will work properly unless it is observed in a research setting that is generalizable. Without getting bogged down in technical details (see Kantowitz, 1992 if you want to slog through details), the best way to select a measure that will work is to be guided by theory. It is poor science to select a measure just because it is easy to obtain. It is almost impossible to select a single measure that captures all the essential characteristics of a complex system, such as a driver in a vehicle. Theory must be used to select a set of measures that are useful and appropriate. Selecting Measures for Driver Distraction It might seem that the best way to measure driver distraction would be simply to ask drivers if they were distracted by some event. This is called obtaining a subjective opinion. We can make this process appear even more scientific by asking the driver to rate (perhaps on a five-point scale from 1-5) how distracted they were. This is called a rating scale. Unfortunately, people are not always able to give subjective ratings in a consistent manner (see Nygren, 1991). Even with a lot of fancy statistical treatments, it can be difficult to interpret subjective ratings. They are used because they are easy to obtain and because sometimes they can be correlated with better measures of distraction. The best measures are objective rather than subjective. This includes measures of how the vehicle is located on the roadway, how hard the driver is pushing on the brake pedal, and how long it takes the driver to react to a signal. Physiological measures are also objective but they are best for determining long-term states of the driver, such as fatigue, rather than specific reactions to particular signals. Since distractions are related to driver attention, theories of attention can help us select the best measures. An important class of measures require the driver to perform another task, called a secondary task, while driving (Kantowitz & Simsek, 2000). If the driver is distracted, there is less attention available to perform the secondary task. So objective performance on the secondary task can be interpreted, using a theory or model of attention, as an index of driver distraction. For example, a secondary task might require a driver to push a button on the steering wheel when an auditory tone is heard inside the vehicle. The time from the onset of this tone until the driver pushes the button, called reaction time, would be a measure of distraction. If reaction time is high, the driver was distracted when the tone came on. If reaction time is low with a rapid response to the tone, we can rule out distraction. However, there is no unique secondary task for measuring driver distraction. Many secondary tasks have been studied and several are useful (Kantowitz & Simsek, 2000). Some typical secondary tasks would include memorizing telephone numbers, doing mental arithmetic and pressing buttons when signals are presented inside the vehicle. But most of these secondary tasks are scored either by reaction time or by proportion of correct responses. So the best measures of driver distraction are time and/or correct responses provided a secondary task has been selected that meets the criteria explained in the first section of this answer. Conclusion There is no single best measure of driver distraction. Objective measures are better than subjective measures. Secondary-task measures of driver distraction offer the best opportunity for success because they can be related to theories of attention. Even so, it is not simple to select the most appropriate secondary task. References Kantowitz, B.H. (1992) Selecting measures for human factors research. Human Factors, 34, 387-398. Kantowitz, B.H. & Simsek, O. (2000, in press) Secondary-task measures of driver workload. In P. Hancock & P. Desmond (Eds) Stress, workload and fatigue. Mahwah, NJ: Erlbaum. Nygren, T.E. (1991) Psychometric properties of subjective workload measurement techniques: Implications for their use in the assessment of perceived mental workload. Human Factors, 33, 17-34. Research article on driver distraction from RoSPA 8/8/00 5:46:27 PM comment to 'nip it in the bud' 8/8/00 5:55:08 PM Where is the reference from the RoSPA? 8/9/00 11:28:20 AM Mr. Murray, please 8/9/00 2:03:41 PM I have that reference 8/9/00 2:56:15 PM driver distraction and driver workload: not the same thing 8/9/00 3:53:52 PM
Research Needs
	7 1