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