to provide a safe central traffic control system that can handle {TAIL ~ emergency vehicles} without {HEAD ~ difficulty} 
to provide a safe central traffic control system that can handle { TAIL ~ emergency vehicles } without { HEAD ~ difficulty }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD