Elsevier

Accident Analysis & Prevention

Volume 37, Issue 6, November 2005, Pages 1093-1101
Accident Analysis & Prevention

Driver's exposure to distractions in their natural driving environment

https://doi.org/10.1016/j.aap.2005.06.007Get rights and content

Abstract

Unobtrusive video camera units were installed in the vehicles of 70 volunteer drivers over 1-week time periods to study drivers’ exposure to distractions. The video data were coded based on a detailed taxonomy of driver distractions along with important contextual variables and driving performance measures. Results show distractions to be a common component of everyday driving. In terms of overall event durations, the most common distractions were eating and drinking (including preparations to eat or drink), distractions inside the vehicle (reaching or looking for an object, manipulating vehicle controls, etc.), and distractions outside the vehicle (often unidentified). Distractions were frequently associated with decreased driving performance, as measured by higher levels of no hands on the steering wheel, eyes directed inside rather than outside the vehicle, and lane wanderings or encroachments. Naturalistic driving studies can provide a useful supplement to more controlled laboratory and field studies to further our understanding of the effects of all types of distractions on driving safety.

Introduction

This paper reports on the second phase of a research project examining driver distraction and its contribution to traffic crashes. The initial phase of the project involved analysis of 5 years of national Crashworthiness Data System (CDS) data to determine the role of driver distraction in U.S. traffic crashes and the specific sources of this distraction (Stutts et al., 2001). The second phase of the project has involved the collection of naturalistic driving data to document drivers’ exposure to specific distracting events and the effects of these events on driving performance.

Driver distraction, and its implicit effects on hazard recognition and vehicle control, has been a prominent topic on highway safety agendas, as well as for the U.S. Congress, state legislatures, the media, and the public at large. Much of this attention stems from the enormous increase in cellular telephone use by drivers and the prospect of similar growth in other in-vehicle technologies such as vehicle navigation systems, wireless Internet capabilities, and wireless messaging. Although the proliferation of new in-vehicle technologies certainly merits concern, the analysis of national crash data documented in the first phase of this study revealed many things distracting drivers and contributing to crashes. The focus of the current paper is on the full range of events and activities that can draw a driver's attention away from the task at hand, delaying recognition of safety threats and impairing effective control of the vehicle.

The National Highway Traffic Safety Administration (NHTSA) has estimated that driver inattention is a contributing factor in 25–30% of crashes (Wang et al., 1996). A variable describing the attention status of the driver was added to the agency's CDS data in 1995. The variable included codes for attentive, sleepy or asleep, and “looked but did not see”, along with 11 specific categories of driver distraction. Table 1, taken from the analysis of 1995–1999 CDS data carried out in the first phase of this project, identifies the primary sources of distraction for those drivers identified as distracted at the time of their crash. Heading the list is events, objects or persons outside the vehicle, followed by adjusting the radio/cassette/CD and other occupants in the vehicle. All other sources of distraction, including cell phones, each accounted for less than 5% of the total.

A similar hierarchy of driving distractions has been found in analyses of state-level crash data from Pennsylvania (Pennsylvania Joint State Government Commission, 2001) and Virginia (Glaze and Ellis, 2003). Although cell phones were somewhat more prominent in these more recent data, they still comprised only 4–5% of the recorded distractions.

Many more studies have been carried out focusing on individual sources of driver distraction, and in particular cellular telephones, vehicle navigation systems, and other in-vehicle technologies (see, e.g., Redelmeier and Tibshirani, 1997, Laberge-Nadeau et al., 2003, Wilson et al., 2003). Most of these studies have been carried out in controlled settings in laboratories, on test tracks, or using driving simulators. As a group, they offer strong evidence that cellular telephones and other in-vehicle technologies can negatively affect some aspects of driving performance.

Largely absent from the literature are reports on drivers’ exposure to various potentially distracting events while engaged in everyday driving. Without information on the frequencies with which drivers engage in such behaviors and the circumstances of this engagement, it is difficult to gauge their potential impact on driving safety. A recent attempt to gather such information relied on photographs of drivers traveling on the New Jersey Turnpike (Johnson et al., 2004). Over 40,000 high quality digital photographs were examined and coded with respect to the presence of cell phones or other distracting behaviors, with results showing cell phones to be the most frequent distraction. NHTSA has also begun incorporating observations of cell phone use into its annual occupant protection use surveys. For the 2004 survey, 5% of drivers were observed using hand-held cell phones, up from 3% 2 years prior (Glassbrenner, 2005).

The current study was intended to further address the need for real-world data on the occurrence and effects of driver distractions, using the specific distractions identified in Table 1 as a starting point. Driver distraction is defined in terms of an object or event that draws one's attention from the task of driving. It is this presence of a triggering event that distinguishes distraction from other forms of driver inattention, which might result from drowsiness or simply being preoccupied by other thoughts. The primary research questions we sought to address were: (1) How often do drivers engage in distracting behaviors? (2) Are there age and sex differences in the occurrences of driver distractions? (3) How do contextual variables such as vehicle movement affect driver distractions? and (4) What are some of the consequences of distractions on driving performance?

Section snippets

Methods

The study involved collecting unobtrusive video data from 70 volunteer participants, driving their own vehicles over a period of a week. The following sections describe the video logging methodology, data collection protocol, data coding and reduction, and data analysis procedures employed.

Characteristics of study participants

Study participants included seven male and seven female drivers in each of the following five age groups: 18–29, 30–39, 40–49, 50–59, and 60+. Thus, each age/sex combination contributed 10% of the total participants (and approximate driving time) to the study.

Results of the pre-driving survey showed that 81% of the participants drove to and from work on a regular basis. The average one-way commute distance was 17.8 miles, while the median distance was lower at 12.0 miles. Overall, participants

Discussion

This study provides some of the first naturalistic data on drivers’ exposure to potential distracting events that have been related to crash involvement. Results showed distractions to be a common component of everyday driving. Altogether, excluding any time spent simply conversing with other passengers in the vehicle, drivers were engaged in one or more potentially distracting activities 14.5% of the total time that their vehicles were moving. Eating and drinking (including preparing to eat or

Acknowledgments

This study was funded by a grant from the AAA Foundation for Traffic Safety, Washington, DC. An earlier version of the paper was presented at the 47th Annual Conference of the Association for the Advancement of Automotive Medicine, September 22–24 in Lisbon, Portugal, and appears in the Annual Proceedings for the conference.

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Present address: Duke University Medical Center, Department of Community & Family Medicine, Durham, NC.

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