threshold determining means for determining {HEAD ~ a velocity threshold value} functionally related to {TAIL ~ said crash displacement value}; and 
functionally related to
threshold determining means for determining { HEAD ~ a velocity threshold value } functionally related to { TAIL ~ said crash displacement value } ; and
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH