{TAIL ~ a second positioning system} arranged in the second vehicle for determining the position of {HEAD ~ the second vehicle}; and 
{ TAIL ~ a second positioning system } arranged in the second vehicle for determining the position of { HEAD ~ the second vehicle } ; and
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH