▁as ▁the ▁Esp in az o ▁del ▁Di ablo — the ▁Dev il ' s ▁Back bone — with ▁many ▁brid ges ▁and ▁t unn els ▁on ▁the ▁route . ▁ ▁Highway ▁ 4 0 D ▁cross es ▁the ▁Bal u arte ▁River ▁and ▁the ▁S inal oa - D ur ango ▁state ▁line ▁on ▁the ▁ ▁Bal u arte ▁Bridge , ▁then ▁the ▁world ' s ▁tall est ▁cable - st ay ed ▁bridge , ▁which ▁was ▁formally ▁inaugur ated ▁in ▁January ▁ 2 0 1 2 . ▁Several ▁ex its ▁provide ▁access ▁to ▁nearby ▁villages , ▁but ▁the ▁only ▁town ▁of ▁size , ▁for ▁which ▁Highway ▁ 4 0 D ▁serves ▁as ▁a ▁by pass , ▁is ▁El ▁Sal to , ▁the ▁seat ▁of ▁P ue blo ▁Nue vo ▁Municip ality . ▁Past ▁El ▁Sal to , ▁the ▁terrain ▁slowly ▁fl att ens , ▁and ▁the ▁Dur ango - M az at lán ▁stretch ▁ends ▁with ▁one ▁more ▁to ll ▁pla za ▁west ▁of ▁Dur ango , ▁for ▁a ▁total ▁of ▁four ▁on ▁the ▁route . ▁ ▁The ▁construction ▁of ▁a ▁highway ▁from ▁Maz at lán ▁to ▁Dur ango ▁was ▁de emed ▁by ▁the ▁S CT ▁in ▁ 2 0 0 8 ▁to ▁be ▁the ▁" larg est ▁project ▁in ▁Mexican ▁highway ▁history " ▁and ▁by ▁President ▁F eli pe ▁Cal der ón ▁to ▁be ▁the ▁" most ▁complex ▁highway ▁in ▁the ▁world ". ▁The ▁highway ▁cross es ▁some ▁of ▁Mexico ' s ▁most ▁ha z ard ous ▁terrain , ▁with