▁U . S . ▁Select ive ▁Service ▁System . ▁This ▁action ▁reduced ▁confusion ▁with ▁the ▁Union ▁Arch ▁Bridge , ▁which ▁car ries ▁the ▁Washington ▁Aqu ed uct ▁and ▁Mac Ar thur ▁Bou lev ard ▁across ▁Cab in ▁John ▁Creek ▁and ▁which ▁some ▁people ▁also ▁called ▁" the ▁Cab in ▁John ▁Bridge ". ▁The ▁bridge ▁was ▁w iden ed ▁from ▁its ▁original ▁ 6 - lane ▁configuration ▁to ▁the ▁current ▁ 1 0 - lane ▁version ▁by ▁ 1 9 9 2 ▁via ▁a ▁third ▁span ▁filling ▁the ▁median ▁between ▁what ▁was ▁originally ▁two ▁separate ▁sp ans . ▁ ▁The ▁American ▁Leg ion ▁Memorial ▁Bridge ▁is ▁an ▁important ▁comm uter ▁route ▁because ▁of ▁its ▁proxim ity ▁to ▁edge ▁cities ▁and ▁high ▁te ch ▁cent ers ▁in ▁Maryland ▁and ▁Virginia . ▁It ▁is ▁the ▁only ▁high ▁volume ▁crossing ▁between ▁Mont gom ery ▁County , ▁Maryland ▁and ▁Fair f ax ▁County , ▁Virginia , ▁the ▁most ▁popul ous ▁count ies ▁in ▁their ▁respective ▁states . ▁ ▁It ▁is ▁also ▁the ▁only ▁major ▁crossing ▁between ▁Maryland ▁and ▁Virginia ▁between ▁the ▁Point ▁of ▁Ro cks ▁Bridge , ▁more ▁than ▁ ▁up stream ▁and ▁the ▁Ch ain ▁Bridge ▁down stream ▁between ▁the ▁Commonwealth ▁of ▁Virginia ▁and ▁the ▁District ▁of ▁Columbia . ▁The ▁only ▁other ▁crossing ▁in ▁this ▁stretch ▁is ▁the ▁low - volume ▁White ' s ▁Fer ry , ▁which ▁is ▁also ▁the ▁last ▁operating ▁fer ry ▁on ▁the ▁Pot om ac . ▁Cong estion ▁on ▁the ▁American ▁Leg ion ▁Bridge ▁and ▁comm uter ▁travel ▁between ▁the ▁western ▁Washington