The equivalent deflexion (Deq) is a new criterion foreseen to be used in Euro NCAP to better assess the chest protection in frontal impact. It has the particularity to discriminate the contribution of two parameters on chest deflexion:
Such a criterion will help car manufacturers to design adequate restraint systems with an appropriate combination of airbag and seat-belt to better protect the vulnerable occupants.
To better understand this new criterion, PSA Peugeot Citroën launched a study to quantify the performances of its current vehicle platforms with respect to the Deq.
Physical tests were analysed on different car platforms with several restraint systems characteristics. Each time, the Hybrid III rodpot and the shoulder belt load were recorded and analysed.
This analysis shows that the sensitivity and reproducibility of the Deq measurements are equivalent than the Rodpot ones.
Because the Deq criterion needs the chest deflexion measured on the Hybrid III rodpot and the shoulder belt load, there are some questions raised by other researchers about sensitivity of Deq and about the pertinence of Deq with respect to Rodpot.
This question is investigated for a nominal restraint system as proposed in Peugeot and Citroën cars. This was done via Design of Experiments made with HIII 50th and HIII 5th models respectively in ODB 64 km/h and Full-width rigid test 50 km/h. The outcome is that for good restraint systems already built to be protective (load limitation less than 5kN), Deq would prevent to use combination of relative high load limitation with very soft airbags, contrary to Rodpot.
But this study is just at its initial phase because of time constraints, because not all the biomechanical criteria were analysed (eg. neck load and moments) and because only one vehicle was investigated. Therefore, we would suggest carrying out the same analysis for restraint solutions widely different than ours.