Abstract: In vehicle frontal impact tests, the safety belt collecting, which normally appears at the upper guide
ring (D-ring) of a safety belt height adjuster, causes severe dummy chest injuries. Two sled tests were conducted
for a vehicle. In one test, the belt acted normally, and in the other test, the belt had collection on the D-ring.
The friction forces, the shoulder belt forces, the chest deflections, and the chest rigidity were measured in the
tests, and then analyzed. The results show that the safety belt collecting enhances D-ring friction force with the
shoulder force increasing by 500 N and the shoulder belt force rising quickly, which makes dummy chest rigidity
decrease, with the dummy chest deflection raising about 20%. Therefore, a new safety belt structural design
should reduce D-ring friction force to prevent safety belt collecting.

Key words: automobile engineering, passive safety, safety belt, upper guide ring (D-ring), safety belt collecting, friction force
chest rigidity, chest deflection