Article
Post-Drive Standing Balance of Vehicle Passengers Using
Wearable Sensors: The Effect of On-Road Driving and
Task Performance
Victor C. Le
1
, Monica L. H. Jones
2
and Kathleen H. Sienko
1,
*
Citation: Le, V.C.; Jones, M.L.H.;
Sienko, K.H. Post-Drive Standing
Balance of Vehicle Passengers Using
Wearable Sensors: The Effect of
On-Road Driving and Task
Performance. Sensors 2021, 21, 4997.
https://doi.org/10.3390/s21154997
Academic Editors: Pietro Picerno,
Andrea Mannini and Clive D’Souza
Received: 4 June 2021
Accepted: 15 July 2021
Published: 23 July 2021
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
Copyright: © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
1
Department of Mechanical Engineering, University of Michigan, 2350 Hayward St.,
Ann Arbor, MI 48109, USA; victle@umich.edu
2
University of Michigan Transportation Research Institute, University of Michigan, 2901 Baxter Rd.,
Ann Arbor, MI 48109, USA; mhaumann@umich.edu
* Correspondence: sienko@umich.edu; Tel.: +1-7346478249
Abstract:
Postural sway has been demonstrated to increase following exposure to different types
of motion. However, limited prior studies have investigated the relationship between exposure to
normative on-road driving conditions and standing balance following the exposure. The purpose of
this on-road study was to quantify the effect of vehicle motion and task performance on passengers’
post-drive standing balance performance. In this study, trunk-based kinematic data were captured
while participants performed a series of balance exercises before and after an on-road driving session
in real-time traffic. Postural sway for all balance exercises increased following the driving session.
Performing a series of ecologically relevant visual-based tasks led to increases in most post-drive
balance metrics such as sway position and velocity. However, the post-drive changes following the
driving session with a task were not significantly different compared to changes observed following
the driving session without a task. The post-drive standing balance performance changes observed
in this study may increase vulnerable users’ risk of falling. Wearable sensors offer an opportunity to
monitor postural sway following in-vehicle exposures.
Keywords: IMU; wearables; standing balance; postural stability; vehicle motion; task performance
1. Introduction
Urban transportation is anticipated to transform through the development of au-
tonomous vehicles (AVs) and other mobility solutions (e.g., ride-sharing services). These
transportation alternatives have the potential to reduce traffic congestion, increase user
productivity, and provide greater access to transportation to a broader population [
1
]. Since
AV users will be passengers, the widespread adoption of mobility solutions will likely
result in an increased number of on-road vehicle passengers compared to drivers. More-
over, accessibility to AVs for broader populations will increase the diversity of passengers
on the road. Accessibility is especially beneficial to older adults for increasing mobility,
independence, and autonomy [
2
]. Across all population segments, users of mobility solu-
tions will be freed from having to drive and will be able to engage in non-driving related
tasks. However, studies of simulated driving and of in-vehicle passengers on a closed
test track have demonstrated that postural control can be negatively affected by motion
exposure [
3
–
8
]. Control of postural sway (especially of the trunk) is crucial for maintaining
upright standing balance [
9
]. A substantial increase in postural sway may increase the risk
of falling after an in-vehicle exposure associated with mobility solutions or AVs [
10
,
11
].
Given a larger and more diverse passenger population, those already susceptible to falling
(e.g., older adults) or those not accustomed to frequent transportation may encounter an
increased risk of injury. Older adults with a history of previous falls are also more likely to
experience subsequent falls and injuries [
12
]. In the worst case, the resulting injuries from a
Sensors 2021, 21, 4997. https://doi.org/10.3390/s21154997 https://www.mdpi.com/journal/sensors
