{HEAD ~ Columns} of vehicles are grouped in {TAIL ~ travel zones} alternating with empty zones , and are laid out in a centrally controlled grid pattern of fastroads  
{ HEAD ~ Columns } of vehicles are grouped in { TAIL ~ travel zones } alternating with empty zones , and are laid out in a centrally controlled grid pattern of fastroads
HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH