The control system guides {HEAD ~ the moving travel zones} through {TAIL ~ the empty zones} of the cross roads without stopping 
through
The control system guides { HEAD ~ the moving travel zones } through { TAIL ~ the empty zones } of the cross roads without stopping
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH