Comparison of the aPLI, FlexPLI with Upper Body Mass, and FlexPLI Pedestrian Legforms in Matched-Pair Vehicle Tests
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Summary
This study addresses the need to improve the biofidelity of pedestrian legform impactors used in vehicle safety assessments. While the Flexible Pedestrian Legform Impactor (FlexPLI) is widely used under Global Technical Regulation No. 9, it lacks an upper body mass, resulting in unrealistic kinematics above the knee and an inability to assess femur bending loads. The research aimed to preliminarily evaluate two advanced legforms designed to address this limitation: the FlexPLI with Upper Body Mass (FlexPLI-UBM), which adds a bolt-on torso attachment, and the Advanced Pedestrian Legform Impactor (aPLI), a redesigned device with integrated upper body mass and modified geometry. The experimental design involved matched-pair vehicle tests using a 2016 Ford Edge. All three legforms were tested at center and outboard impact locations. Due to launcher limitations with the heavier advanced legforms, tests were conducted at 9 m/s rather than the standard 11.1 m/s. To account for the increased mass and altered center of gravity, impact heights were adjusted: the FlexPLI was tested at 75 mm, the FlexPLI-UBM at 63 mm, and the aPLI at 25 mm relative to the ground reference level. The study compared kinematic responses and injury metrics, including femur and tibia bending moments and knee ligament elongations. Results indicated that the addition of upper body mass significantly altered impact kinematics. During the rebound phase, both advanced legforms maintained a forward pitch toward the vehicle, whereas the standard FlexPLI pitched rearward. Mechanically, the FlexPLI-UBM and aPLI exhibited substantially higher femur bending moments and greater medial and posterior collateral ligament (MCL/PCL) elongations compared to the FlexPLI. Conversely, tibia bending moments remained similar across all three devices, suggesting that upper body modifications did not affect lower leg response. Anterior cruciate ligament (ACL) responses varied; the aPLI showed lower initial ACL elongation but a significant secondary peak during rebound, attributed to its vertically oriented ligaments, while the FlexPLI-UBM and FlexPLI showed similar ACL responses due to shared ligament geometry. The findings suggest that incorporating upper body mass improves the realism of femur loading and knee kinematics, potentially allowing for a single legform test to assess both upper and lower leg injuries. However, the study notes that increased femur bending may result from both the added mass and the lower impact heights required for stability. Further testing is needed to isolate these variables and validate the advanced legforms for regulatory use.
Key finding
The addition of upper body mass to pedestrian legform impactors significantly increases femur bending moments and knee ligament elongations while maintaining similar tibia bending moments compared to the standard FlexPLI.
Methodology
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Provenance
The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).
| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | rosap | — | — | 2 | 2026-05-23 |
| archive | success | — | — | — | 1 | 2026-05-23 |
| extract | success | cached | — | — | 2 | 2026-06-10 |
| clean | success | — | — | — | 1 | 2026-06-01 |
| chunk | success | — | — | — | 1 | 2026-06-01 |
| embed | success | — | — | — | 1 | 2026-06-02 |
| enrich | success | — | — | — | 1 | 2026-05-23 |
| promote | success | — | — | — | 1 | 2026-05-23 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 3 | 2026-06-10 |
| tag | success | vector_similarity | — | — | 24 | 2026-06-11 |
| verify | success | — | — | — | 2 | 2026-06-10 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.
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