Postural and Muscular Responses of Car Occupants under Pre-Crash Conditions
Doctoral thesis, 2021

Advanced integrated safety technologies in modern cars such as collision avoidance intervention and pre-crash activated restraint systems require comprehensive research on how vehicle occupants respond to these systems. The aim of this thesis is to provide insights into car passengers’ body kinematics and muscle activations in representative pre-crash circumstances with respect to two belt configurations (i.e., standard versus pre-pretensioner). Another objective is to explore the influence of occupants’ individual characteristics — namely age, stature, and sex — on their body kinematics. A complementary objective is to provide validation data for human body models (HBMs).

A set of in-vehicle experiments was carried out in which front-row passengers were traveling at 73 km/h and subjected to autonomous lane changes and lane changes combined with braking, each with two belt configurations: standard and reversible pre-pretensioner belts. Volunteer muscle activations were measured by the surface electromyography (EMG) technique. Transformation of coordinates corresponding to several film targets attached to the head and upper torso was used to calculate the kinematics in 3-D. The volunteers’ EMG and kinematics were processed, and the quantified kinematics were statistically explored using principal component analysis and linear mixed model.

Compared to the standard belt, pre-tensioning the seat belt prior to the maneuvers reduced lateral and forward displacements of the head and upper torso significantly. Seat belt pre-tensioning was also associated with earlier muscle activation onset and significantly lower activation amplitude for specific muscles. The influence of sex, stature, and their interaction on the head and upper torso kinematics were found statistically significant but accounted for a small amount of variance. A statistical model was developed which can predict head and upper torso kinematics of occupants with different stature and sex.

The data provided in this thesis can be used for further enhancement and validation of HBMs. Consequently, the design of integrated safety systems in modern cars can benefit from more biofidelic models representing a wide range of population more accurately. Further statistical investigations for other types of omnidirectional loading scenarios and, preferably with a larger and more diverse sample space, are required to establish more accurate statistical models that can be generalized to the whole population.

principal component analysis

linear mixed model

pre‐pretensioner belt

vehicle occupant kinematics


evasive maneuvers

human body model


lane change

Vasa B-salen, Vasa Hus 2, Vera Sandbergs Alle 8, Göteborg (physical attendance by invitation only).
Opponent: universitetslektor (associate professor) Francisco José López-Valdés, från Comillas Pontifical Universitet i Madrid, Spain


Ghazaleh Ghaffari

Chalmers, Mechanics and Maritime Sciences, Vehicle Safety, Injury Prevention

Passenger kinematics in Lane change and Lane change with Braking Manoeuvres using two belt configurations: standard and reversible pre‐pretensioner

2018 IRCOBI Conference Proceedings- International Research Council on the Biomechanics of Injury,; (2018)p. 493-511

Paper in proceeding

Female kinematics and muscle responses in lane change and lane change with braking maneuvers

Traffic Injury Prevention,; Vol. 22(2021)p. 236-241

Journal article

Ghaffari G, Iraeus J, and Davidsson J. The effect of age, stature, and sex on passenger kinematics in lane change maneuvers

In spite of great improvements in vehicle safety systems, still a large number of car occupants die or are severely injured due to car accidents. The few seconds before a car accident takes place (i.e., ‘the pre-crash period’) is a determining factor for the accident outcome in terms of human damage. Recent developments of crash avoidance and restraint systems (such as autonomous emergency braking and pre-tensioner seat belts) require extensive research about the pre-crash period. In this work, the body displacements, and muscular responses of the car passengers during pre-crash evasive maneuvers are comprehensively studied. My results show that pre-pretensioner seat belts (i.e., the seat belts which are automatically tensioned prior to the pre-crash maneuvers) are more capable of restraining the passenger’s head and torso displacements than standard seat belts. Furthermore, a statistical model is developed in this work that can predict the body displacement of car passengers based on their sex and height. The information provided in this thesis can be used to develop and evaluate computational human body models and to improve the current state-of-art automotive safety technologies.

Active human body models for virtual occupant response, step 3

VINNOVA (2014-03931), 2014-10-01 -- 2017-12-31.

Future Occupant Safety for Crashes in Cars (OSCCAR)

European Commission (EC) (769947-OSCCAR), 2018-06-01 -- 2021-05-31.

Subject Categories

Mechanical Engineering

Medical Engineering

Electrical Engineering, Electronic Engineering, Information Engineering

Areas of Advance




Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5002


Chalmers University of Technology

Vasa B-salen, Vasa Hus 2, Vera Sandbergs Alle 8, Göteborg (physical attendance by invitation only).


Opponent: universitetslektor (associate professor) Francisco José López-Valdés, från Comillas Pontifical Universitet i Madrid, Spain

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