208041 Measuring teen driving exposure in Michigan: Demographic and behavioral characteristics

Wednesday, November 11, 2009: 1:30 PM

Johnathon P. Ehsani, MPH , Center for Injury Prevention among Youth, School of Public Health, University of Michigan, Ann Arbor, MI
Jean T. Shope, MSPH, PhD , Transportation Research Institute, University of Michigan, Ann Arbor, MI
Tenaya M. Sunbury, MS , School of Public Health, University of Michigan, Ann Arbor, MI
Byoung-Suk Kweon, PhD , School of Natural Resources and Environment, Research Investigator & Adjunct Assistant Professor, University of Michigan, Ann Arbor, MI

Motor vehicle crashes kill and injure more US children and young adults than any other cause. Young drivers, especially men, and drivers carrying passengers are particularly at risk. To understand the nature and magnitude of crash risk under various driving conditions, it is necessary to adjust rates for driving exposure. However, our ability to measure teen driving exposure is poor. The National Household Travel Survey (NHTS) does not sample enough young drivers to provide accurate estimates of driving exposure.


We analyzed data provided by the Michigan Department of Transportation, which undertook a state-wide self-reported survey of 14,315 households in 2004 and 2005. To understand driving exposure by age group, the analysis used mean driving time and mean number of trips within a 48 hour travel diary period. Driving exposure was stratified by age, demographics, and trip characteristics to describe exposure patterns. Analyses are underway to determine miles driven.


In the 48-hour period, 586 of 917 16-17 year olds reported driving. They drove an average of 6.46 trips and 83 minutes, with men driving longer than women (86 minutes versus 79 minutes).

The mode number of trips across all age groups was four, with 16-17 year old drivers making fewer trips and driving fewer minutes than 18-24 (mean trips = 6.88, 119 minutes) and 35-64 year old drivers (mean trips =7.65, 125 minutes).


This information could be used in crash rates to refine efforts to describe and prevent teen motor vehicle injuries and fatalities.

Learning Objectives:
1. Explain the need for accurate measures of driving exposure for teen drivers. 2. Describe differences in driving exposure by age in the state of Michigan. 3. Recognize the use and limitations of travel diary data to quantify driving exposure.

Keywords: Motor Vehicles, Youth

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: I am undertaking a PhD in health behavior and health education with a focus on adolescent risk behavior.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.