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