a communication device arranged in the second vehicle and which communicates the position of {HEAD ~ the second vehicle} as determined by {TAIL ~ said second positioning system} to the first vehicle 
a communication device arranged in the second vehicle and which communicates the position of { HEAD ~ the second vehicle } as determined by { TAIL ~ said second positioning system } to the first vehicle
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH