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