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