Evaluating the Efficacy of Belt Positioning Booster Seat Design (High-back, Low-back and Height-less booster) in Frontal and Far Side Oblique Impacts

Principal Investigator: Aditya Belwadi, PhD, The Children’s Hospital of Philadelphia

This study examines anthropomorphic test device (ATD) kinematics and kinetics as a function of variability of booster seat design and impact direction. The focus is on evaluating the effect of various routing configurations for booster seat designs on the protection afforded in far-side impacts – both lateral and oblique crash modes. The data generated from this project may benefit child seat and vehicle manufacturers, as well as policymakers and the public, as newer restraint technologies to mitigate injury in pediatric occupants are developed.

Principal Investigator: Aditya Belwadi, PhD, The Children’s Hospital of Philadelphia

Below is an executive summary of this project. Please note that this summary describes results and interpretation that may not be final. Final interpretation of results will be in the peer-reviewed literature.

Project motivation

Child safety seats present a complex design challenge: to create a device that is easy to use, adjusts to children’s changing sizes, is capable of being properly fitted into the wide variety of vehicles, and is affordable. However, when it comes to booster seats, vehicle seat belt geometry also plays a role. Belt-positioning booster seats are recommended for children who use vehicle seat belts as primary restraints but who are too small to obtain good belt fit. The booster seat positions the child and routes the vehicle seat belt so that the belt interacts with key parts of the skeletal structure - the clavicle and the pelvis. The vast majority of previous research evaluating the protection afforded by booster seats has been conducted in frontal crash conditions. However, the importance of other crash conditions - particularly side impact - in child occupant protection has received substantial attention lately. An upgrade to the FMVSS213 regulation has recently been proposed to include side impact protection; real-world data suggests this crash direction is over represented in fatalities and serious injuries for children in child restraints and booster seats. CChIPS has studied this scenario in a line of research examining the performance of FFCRS in oblique lateral crashes (Hauschild et al, AAAM 2015, 2016). Little attention, however, has been placed on the performance of booster seats in this crash direction. Thus, the current CChIPS project builds on this previous work, focusing on evaluating the effect of various vehicle belt routing configurations for booster seat designs on protection afforded in a variety of crash directions – including frontal, lateral, and oblique crash modes - and compares lowback, highback, inflatable, and heightless booster seat designs.

Specific aims

To quantify the effect of various booster seat designs and belt routing strategies on booster seat performance in frontal, farside lateral, and oblique impacts.


Step 1a: Selection of booster seats for the evaluation

A selection of seats based on inputs from the IAB and historical booster seat fit data from IIHS

Step 1b: Sled testing utilizing the Q6 anthropomorphic test dummy (ATD)

Simulated frontal (0 degrees), oblique (30 degrees) and lateral (80 degrees) tests on a sled system

Step 2: Finite Element (FE) Simulation utilizing previously developed CChIPS FE models

FE simulations varying the “D” ring position to understand belt rollout and injury metrics

  • Sled Testing: Forty sled tests were conducted using an instrumented Q6 ATD with a hip-liner and abdominal pressure sensors restrained on NHTSA’s 2017 FMVSS213 NPRM test bench. Tests were conducted with two highback, two lowback, one inflatable, one heightless and one no-booster seat condition. All restraint types were evaluated in three PDOFs (0 degrees, 30 degrees and 80 degrees) with each condition repeated twice. High-speed video data, sled acceleration along with ATD kinetics were recorded. For all booster seat types, kinetic data – head and chest resultant acceleration, HIC15 and chest deflection - were all within reference thresholds (IARVs) as specified for frontal impacts as part of the FMVSS213 test standard. Kinematic tracking from high-speed video data revealed that the highback booster had the highest normalized forward excursion. This is due to a more forward initial position of the occupant, and may also have been influenced by the potential flexing of the booster seat back. In addition, we observed an increase in torso angle for the no booster and heightless CRS condition (from initial seating position) as compared to a decrease in torso angle for the other restraint types. For the heightless booster seat, we believe this increase in torso angle is due to the interaction of the belt with the ATD. During the crash event, the shoulder belt moved towards the neck and underneath the armpit thus restraining the upper torso while the lap belt engaged the pelvis later in the crash sequence. This caused the ATD's torso to "arch" open for this booster seat. It should be noted that the forces recorded on the neck were below the IARV limits. It is unknown how these kinematics will affect injury risk in a frontal crash. Currently, additional research is being carried out to understand further.
  • Finite Element Modeling: In order to further examine the effect of the shoulder belt position, the “D” ring location was artificially varied in a fully validated FMVSS213 test bench model. Three conditions for “D” ring were selected - 213 bench, small hatchback, and large crossover - and evaluated with the Q6 ATD model for highback, lowback, and heightless seats. There was no difference in ATD kinetics for the different "D" ring conditions in the lowback and heightless seats. However, for the high-back boosters it was found that altering the “D” ring position played a role, with both HIC15 and head resultant accelerations being higher than those recorded for the backless and heightless boosters across the three conditions. However, across the board, HIC15 and head resultant accelerations were below the IARV recommended limits.

Project Team Member

Kristy Arbogast, PhD, Children’s Hospital of Philadelphia

Comparison of lowback (LBB), highback (HBB), and heightless boosters in frontal (0 degrees), oblique (30 degrees) and lateral (80 degrees) impacts.


Evan Bisirri, Drexel University; Nhat Duong, Drexel University; Seth Fein, University of Pennsylvania; Jalaj Maheshwari, University of Pennsylvania

IAB Mentors

Keith Nagelski, Britax Child Safety Inc.; Michael Kulig, Calspan Corporation; Emily Thomas, Consumer Reports; Eric Dahle, Evenflo Company Inc.; Amanda Taylor, Federal Aviation Administration; Zine Ben Aoun, General Motors Holdings LLC; Julie Kleinert, General Motors Holdings LLC; Mark LaPlante, Graco Children’s Products Inc.; Jerry Wang, Humanetics Innovative Solutions Inc.; Jessica Jermakian, Insurance Institute for Highway Safety; Russ Davidson, Lear Corporation; Mladen Hume, Lear Corporation; Eric Veine, Lear Corporation; Arjun Yetukuri, Lear Corporation; Jon Sumroy, mifold; John Combest, Nissan Motor Company; Hiromasa Tanji, Takata Corporation; Schuyler St. Lawrence, Toyota USA; Barbara Birkenshaw, Volkswagen Group of America, Inc.; Uwe Meissner, Technical Advisor