nor ▁features ▁ 3 3 0 ▁Roman ▁stone ▁brid ges ▁for ▁traffic , ▁ 3 4 ▁Roman ▁tim ber ▁brid ges ▁and ▁ 5 4 ▁Roman ▁aqu ed uct ▁brid ges , ▁a ▁substantial ▁part ▁still ▁standing ▁and ▁even ▁used ▁to ▁carry ▁vehicles . ▁A ▁more ▁complete ▁survey ▁by ▁the ▁Italian ▁scholar ▁Vitt orio ▁Gall ia z zo ▁found ▁ 9 3 1 ▁Roman ▁brid ges , ▁mostly ▁of ▁stone , ▁in ▁as ▁many ▁as ▁ 2 6 ▁different ▁countries ▁( including ▁former ▁Y ug oslav ia ; ▁see ▁right ▁table ). ▁ ▁Roman ▁arch ▁brid ges ▁were ▁usually ▁sem ic irc ular , ▁although ▁a ▁few ▁were ▁segment al ▁( such ▁as ▁Al con ét ar ▁Bridge ). ▁A ▁segment al ▁arch ▁is ▁an ▁arch ▁that ▁is ▁less ▁than ▁a ▁sem ic irc le . ▁The ▁advantages ▁of ▁the ▁segment al ▁arch ▁bridge ▁were ▁that ▁it ▁allowed ▁great ▁amounts ▁of ▁flo od ▁water ▁to ▁pass ▁under ▁it , ▁which ▁would ▁prevent ▁the ▁bridge ▁from ▁being ▁swe pt ▁away ▁during ▁flo ods ▁and ▁the ▁bridge ▁itself ▁could ▁be ▁more ▁light weight . ▁Gener ally , ▁Roman ▁brid ges ▁featured ▁w edge - sh aped ▁primary ▁arch ▁stones ▁( vous so irs ) ▁of ▁the ▁same ▁in ▁size ▁and ▁shape . ▁The ▁Rom ans ▁built ▁both ▁single ▁sp ans ▁and ▁length y ▁multiple ▁arch ▁aqu ed uct s , ▁such ▁as ▁the ▁Pont ▁du ▁Gard ▁and ▁Seg ov ia ▁Aqu ed uct . ▁Their ▁brid ges ▁featured ▁from ▁an ▁early ▁time ▁on wards ▁flo