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Non-Driving Occupant Posture and Activities in Moving Vehicles

The objective of this project was to increase the scientific understanding of typical front-seat passenger postures through a naturalistic study observing in-vehicle behaviors.

University of Michigan Transportation Research Institute (UMTRI)

The Problem

Recent studies suggest a relationship between crash injury risk and occupant posture, particularly in postures different from those used with anthropomorphic test devices (ATDs) in crash testing. As automated vehicles take to the roads, the range of postures is expected to increase in comparison to today’s upright seating positions.

The Question

What postures, seat adjustment positions, and activities are prevalent among vehicle passengers?

What We Did

The research team installed video cameras in 75 vehicle cabins to monitor the postures and activities of 306 unique front-seat passengers over a total of 2,733 trips. During these trips, 13,638 frames were coded for passenger posture, seat belt use and position, activities, seat back angle, and seating behavior. Each frame represented roughly four minutes of in-vehicle travel time. The trip durations were similar to the general population of U.S. travelers, with 5% of trips longer than 54 minutes.

The Result

Research concluded in February 2020 and will be presented at the 2020 Association for the Advancement of Automotive Medicine (AAAM), in October 2020 in Portland, OR.


The study determined:


  1. Occupant resting behavior was observed more frequently in longer-duration trips and when traveling at higher speeds, while phone use increased and talking decreased the longer in car.
  2. In this sample size, seat position rarely changed, and it did not move at all in 53% of observed vehicles.
  3. Observations of self-selected seating positions and activities may help to understand future automated vehicle occupant behavior, and aid in developing automated vehicle crash protection assessment while informing interior designs.


This project is in collaboration with the University of Michigan Transportation Research Institute.