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