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Sled Laboratory Research Overview
The Sled Lab, led by CIRP Principal Scientist and Drexel University faculty member Valentina Graci, PhD, is located on the Drexel University campus. Dr. Graci and her fellow CIRP researchers have designed and built several innovative custom-made, low-acceleration sleds to simulate different types of vehicle crash avoidance maneuvers (e.g., emergency braking, evasive swerving) that vehicle occupants experience on the road. Dr. Graci is currently investigating the influence of automatic emergency braking (AEB) on vehicle occupants' posture as over 90% of vehicles come standard with AEB in 2024 and it will become standard in all vehicles in 2029.
In addition to automotive safety biomechanics, Dr. Graci's lab also focuses on the development and testing of medical devices for injury prevention in older adults. Studying older adults at a children's hospital may be surprising, but detailed understanding of injury mechanisms in older adults (e.g. falls, pressure injuries) can sometimes be done more easily and these studies help inform the investigation of injury mechanisms in children.

The National Highway Traffic Safety Administration will soon require automatic emergency braking (AEB) and pedestrian AEB in all new vehicles, and many vehicles already have aspects of these technologies. AEB may place vehicle occupants out of the optimal position within the seat belt before a potential crash. Therefore, in case of a subsequent collision, vehicles that have AEB systems with high peak acceleration and jerk (i.e., resulting in an abrupt vehicle stop and more occupant movement) may expose occupants to increased injury risk if a subsequent crash occurs, displacing the occupant even further.
The Sled Lab was the first group to shift their investigative focus from the effectiveness of the AEB in stopping the vehicle to avoid contacting other objects or persons outside the vehicle (i.e., vulnerable road users or another car) to how the AEB achieves that stop so that the risk to the occupant inside the vehicle is not elevated.
Related Publications
Quantitative characterization of AEB pulses across the modern fleet
Traffic Injury Prevention. September, 2021
Efficacy of Automatic Emergency Braking Among Risky Drivers Using Counterfactual Simulations from the SHPR2 Naturalistic Driving Study
Safety Science. August, 2020
Head contacts in second-row pediatric occupants when the front-seat is reclined during automated emergency braking
Computer Methods in Biomechanics and Biomedical Engineering. November, 2022

In recent years, crash avoidance maneuvers have been a topic of focus since it is during these maneuvers that vehicle occupants may move outside the optimal restrained position, potentially leading to an increased risk of injury during a subsequent crash. Child and teen vehicle passengers may be less aware of impending maneuvers and, therefore, less prepared to maintain optimal restrained posture through bracing and other strategies.
The Sled Lab is working to characterize occupant position during a variety of crash avoidance maneuvers (e.g., emergency braking, lateral furrowing, and evasive swerving) both in the laboratory and in real vehicles. These data can inform automotive industry strategies for improving safety restraints for vehicle passengers of a range of ages.
Related Publications
Age Differences in Occupant Motion during Simulated In-Vehicle Swerving Maneuvers
International Journal of Environmental Research and Public Health. March, 2020
Characterization of the motion of booster-seated children during simulated in-vehicle precrash maneuvers
Traffic Injury Prevention. August, 2019
Effect of automated versus manual emergency braking on rear seat adult and pediatric occupant precrash motion
Traffic Injury Prevention. August, 2019

Pre-pretensioner seat belts are designed to remove the slack of the belt during a crash avoidance maneuver to keep the occupants from being displaced out-of-position before a potential crash may occur. Once positioned within the seat belt, the occupant can benefit from the restraint's effectiveness in controlling vehicle occupants' motion during the crash. The Sled Lab is exploring how pre-pretensioner seat belts perform when the occupant is not optimally seated but leaning forward – a common position real people assume in a car. This line of work highlights the potential efficacy of an electronic reversible pre-pretensioner seat belt in repositioning occupants before a crash occurs.
Related Publications
Repositioning forward-leaning vehicle occupants with a pre-pretensioner belt and a startle-based warning in pre-crash scenarios
Traffic Injury Prevention. August, 2022
The effect of vehicle countermeasures and age on human volunteer kinematics during evasive swerving events
Traffic Injury Prevention. November, 2019

Reclined seating will be a likely reality in highly automated vehicles as passengers will take the opportunity to relax once the driving task is completely relinquished to the car. The Sled Lab was the first to investigate the motion of booster-seated children in reclined seating to understand injury risk. This research highlights that booster seats may be beneficial in these reclined configurations to mitigate abdominal injuries but not spinal injuries. Small female occupants have recently been identified as being at higher risk of injury than their averaged-sized male counterparts. The Sled Lab team aims to understand how vehicle safety countermeasures for children can also inform solutions for small adult occupants.
Related Publications
The Influence of a Booster Seat on the Motion of the Reclined Small Female Anthropomorphic Test Device in Low-Acceleration Far-Side Lateral Oblique Impacts
Journal of Biomechanical Engineering. March 2024
Characterizing neck and spinal response in booster seated reclined children in frontal impacts
Traffic Injury Prevention. June, 2023
The effect of a moderately reclined seat-back angle on the kinematics of the Large-Omnidirectional Child Anthropomorphic Test Device with and without a belt-positioning booster in frontal crashes
Traffic Injury Prevention. July, 2022

The Sled Lab is focused on identifying strategies to accelerate reaction times to take over a highly automated vehicle in critical scenarios. Highly automated vehicles may lead to passengers being out-of-the-loop of driving tasks, and slower reaction times in critical events may increase the risk of crashes.
In neuromotor rehabilitation research, the startle reflex has been shown to be effective in accelerating reaction time in simple manual tasks. The Sled Lab team innovatively translates this knowledge across disciplines and explored the effectiveness of the startle reflex in accelerating the take-over of driving tasks in experienced and inexperienced drivers. They have also explored strategies to detect brain activity associated with the startle reflex with an eye to the development of future technology for injury prevention.
Related Publications
Localizing EEG Recordings Associated With a Balance Threat During Unexpected Postural Translations in Young and Elderly Adults
IEEE Transactions on Neural Systems and Rehabilitation Engineering. November, 2023
The effect of a startle-based warning, age, sex, and secondary task on takeover actions in critical autonomous driving scenarios
Frontiers in Bioengineering and Biotechnology. March, 2023
Characterizing driver take-over accuracy: effect of age, sex, startle, and secondary task
Biomedical Sciences Instrumentation. April, 2021