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Article Excerpt
INTRODUCTION
The Problem and the Approach
Driver distraction as a research topic is currently popular, for good reason. Automobiles and trucks are undergoing large changes in terms of the new sensor, computer, and communication technology they incorporate. As part of this change within the industry, there is now momentum to add driver-interactive information technology (IT) to the vehicle. This is not only to increase safety and make vehicle control more reliable (so-called safety-enhancing technology) but also to entertain the driver and passengers on long trips or traffic-snarled commutes and to provide an increased capability to do work other than driving the vehicle. The concern is whether such technology compromises safety. Cell telephone communication is now extensive, and E-mail and other forms of computer interaction are not far behind. So the current concern for the safety impacts of driver distraction attributable to new IT devices is not an imagined problem: It is real. Both crash data and experimental research have already pointed to the evidence.
But what is driver distraction, and how well is it understood? This paper develops a definition of driver distraction, discusses its elements from the viewpoint of control engineering, and offers a framework for analysis.
Distraction of the human controller of a highway vehicle is regarded as a disturbance at various points in a classical feedback loop representation of control of a vehicle. The type and locus of the disturbance are determiners of the vehicle response, as are the frequency and duration of attention away from the driving task. Operationally, if there is no effect of distraction on control, there is no distraction.
I start with a continuous classical control model. The relevance of some advanced control concepts, such as discrete sampling, preview, and internal modeling, are then related to the sensory and cognitive aspects of distraction.
No claim is made that this framework will fill all needs. Rathel, it is suggested as an alternative that emphasizes the dynamics of driving performance as a function of particular attributes of distraction. However, unlike several complex qualitative models of distraction causality and effects on performance, the proposed control model is sufficiently simple and explicit to have a degree of predictive capability.
Many terms are currently in use by human factors practitioners to refer to aspects of human behavior in controlling a vehicle or process, and most seem somehow related to distraction. Some are older terms from psychology, such as attention. Others are newer and currently in vogue, such as mental workload and situation awareness. This report seeks to interrelate several such relevant terms in the vehicle driving distraction context.
Background of Driver Distraction
Driver distraction is currently attracting considerable attention in the highway safety research community (Anderson, Abdalla, Pomietto, Goldberg, & Clement, 2001; Cole & Hughes, 1988). Vehicle crash databases have revealed much information pointing to the negative effects of distraction on safety. Wang, Knipling, and Goodman (1996) estimated from government crash databases that 12% of crashes involve what they called distraction and 9% were in a category called looked but did not see. Stutts, Reinfurt, Staplin, and Rodgman (2001) reviewed the same databases 5 years later and estimated that 49% of drivers in crashes had been inattentive, of which 8% were distracted and 5% looked but did not see. (The numerical differences may be attributable to differences in subjective interpretation of data.)
Eye movement measurement is probably the most popular way to measure distraction (Liu & Pentland, 1997). Other studies have explicitly looked at side tasks within the vehicle (Hancock, 1999; Horrey & Wickens, 2002; Lee, Caven, Haake, & Brown, 2001; Lee, McGehee, Brown, & Reyes, 2002). The National Highway Traffic Safety Administration (NHTSA) has sponsored several national forums on the topic of driver distraction (Llaneras, 2000).
Some terms found in the literature seem to relate to driver distraction positively and some negatively. For example, attention, alertness, vigilance, focus, and situation awareness are positive, whereas mental load, stress, fatigue, and drowsiness are negative. None of these terms means the same thing as another; there are connotations that are different but subtle. It is tacitly assumed that the reader of papers in the literature understands the meaning of these terms, but meetings on the topic evidence confusion and lack of operational definition. Continuing efforts are needed to clarify their meanings and discriminate among them.
Attention and focus are the two terms that have been most closely associated with distraction. M. Goodman (personal communication, 2002) contends that there can be many taxonomies, so to seek universal acceptance on one taxonomy or definition may be fruitless: It is sufficient to operationally define distraction in the context of a particular study. The National Highway Traffic Safety Administration (NHTSA) has sometimes found it convenient to separate distraction attributable to fatigue, drowsiness, or sleepiness from the "looked but did not see" phenomenon in partitioning crash data.
Let driver distraction be defined as a process or condition that draws away driver attention, thereby disturbing driving control. Justification for such a definition might be found in the Webster's Third New International Dictionary (1965) definition: from the Latin dis (apart) + trahere (draw or pull), "to draw or cause to turn away from an original position, goal, purpose, direction, association or interest." Webster's listed synonyms are divide, separate, harass, and confound. Roget's International Thesaurus (1977) lists other synonyms: discompose, disincline, divert. From the Fernald (1947) book of synonyms the terms disturb, perturb, remove, detach, steal, withdraw, purloin, and confuse can be added. All of these terms imply compromise in safety and also connote what disturbance means to a control engineer, in terms of its effect on system performance.
Current research in driver distraction essentially looks at an array of factors that are lumped together as distractors because they result in diminished driving performance (and bring the vehicle closer to collision with other vehicles, roadside objects, or pedestrians). Eye movements and braking/steering response are currently regarded as the "gold standard" of distraction-dependent measures of system performance.
A CONTROL THEORY FRAMEWORK OF MINIMAL FUNCTIONAL ELEMENTS
The framework suggested for considering driver distraction is that of the conventional control loop; see Figure 1.
[FIGURE 1 OMITTED]
The idea of a control model is not new to driving research. The continuous functions of lane and headway keeping have long been modeled using dynamic models (Allen, Rosenthal, Aponso, et al., 1998; Allen, Rosenthal, & Christos, 1998; Levison, 1993, 1998). Discrete maneuvers, although obviously differing from lane keeping, have long been recognized as subsuming continuous control (Michon, 1993). Computer algorithm-based models have also been applied to driving (Anderson & Lebiere, 1998). Jagacinski and Flach (2003) provided an introductory text in control aimed at nonengineers.
Figure 1 shows five blocks of the proposed model designated by boldface letters:
1. The intending block, I, generates a priority-ordered sequence of near-term driving goals: a time variable I (whether safe or foolishly unsafe, and on whatever time scale is convenient) to follow a given lane, maintain a certain speed, maintain a certain distance behind a lead car, pass, perform a turning maneuver, and so forth. I constitutes the "original position" in Webster's definition of distraction. One can assume that no matter what additional tasks the driver undertakes while driving, the basic intention remains to drive safely. [I.sup.*] represents a driving goal modification, such as a sudden demand to make a right turn from...
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