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Child occupant protection in buses and coaches: A parametric study of restraint systems in frontal crashes
M Valdano1, S Roka2, O Martinez2
1MOBIOS lab, IIT, ICAI, Universidad Pontificia Comillas, Madrid, Spain.
Insights
Child restraint systems in buses are crucial. Three-point seatbelts with booster seats significantly reduce head excursion in frontal crashes, unlike two-point seatbelts, enhancing child safety.
Area of Science:
- Automotive Safety Engineering
- Biomechanics
- Child Passenger Safety
Background:
- UN Regulation No. 170 mandates improved child protection in buses and coaches.
- Assessing child occupant kinematics and spinal loads in bus crashes is vital for regulatory compliance and safety improvements.
Purpose of the Study:
- To evaluate head kinematics and spinal loads of 3- and 6-year-old child models in bus seats during frontal crashes.
- To assess the effectiveness of various child restraint systems (CRS) under UN Regulation No. 170 guidelines.
Main Methods:
- Parametric computational study using PIPER Human Body Model (HBM) for 3- and 6-year-old children.
- Simulated frontal crash scenarios (delta-v 30 km/h) with different belt systems (2-point, 3-point) and CRS (none, booster, ISOFIX).
- Assessed head excursions and spinal loads across 14 simulated conditions.
Main Results:
- Two-point seatbelts resulted in excessive head excursions (>550 mm), risking head contact.
- Three-point seatbelts reduced head excursions significantly (205-321 mm for 3-year-olds, 229-316 mm for 6-year-olds).
- Booster seats with 3-point seatbelts were most effective; ISOFIX provided marginal additional benefit.
Conclusions:
- Two-point seatbelts are insufficient for adequate child restraint in buses; three-point seatbelts are essential.
- Combining 3-point seatbelts with booster seats effectively manages child occupant kinematics in frontal bus crashes.
- Transitioning to 3-point seatbelts is the most critical factor for reducing child injury risk in buses.
Objective:
The newly approved UN Regulation No. 170 addresses the proper protection of children in buses and coaches. This study aims to evaluate the head kinematics and spinal loads of 3- and 6-year-old child human body models with and without a child restraint system (CRS) in bus seats under frontal crash scenarios for buses and coaches, in light of the new UN regulation.
Methods:
A parametric computational study was conducted using the PIPER Human Body Model (HBM) to represent both a 3-year-old and a 6-year-old child. The HBM was seated in a bus seat, with and without a booster seat, and exposed to a frontal collision scenario. 14 conditions were simulated: 2 child sizes, x 2 belt systems (2-point and 3-point) x 3 CRS conditions (none, booster seat without harness, booster with ISOFIX) + unrestrained with each child size (n = 2). A delta-v of 30 km/h was applied in accordance with UNECE R80 and R170. Head kinematics and spinal loads were assessed.
Results:
The 2-point seatbelt configurations for 3-year-old and 6-year-old child models resulted in head excursions exceeding 550 mm, even with a booster seat, potentially leading to head contact with the forward seat. In contrast, 3-point seatbelts (with and without a booster seat) reduced these excursions to 205-321 mm for 3-year-olds and 229-316 mm for 6-year-olds compared with the 2-point configuration. The most effective configuration was the 3-point seatbelt paired with a booster seat, which further reduced head excursion by 77-109 mm compared to non-booster-seat setups. The integration of ISOFIX anchorages showed only marginal improvement (about 10 mm) in head excursion reduction compared to non-ISOFIX installations.
Conclusions:
This research highlights that 2-point seatbelts in buses and coaches may be insufficient to provide adequate restraint for child occupants, leading to excessive head excursion in frontal crashes. Conversely, 3-point seatbelts combined with booster seat effectively managed occupant kinematics, preventing contact with the interior environment. Although ISOFIX offered some benefits, the most significant factor in reducing injury risk is the transition from 2-point to 3-point seatbelts. Further studies focusing on younger children and other child restraint systems may be needed to fully evaluate their safety.
