“Wedon’thaverushhoursanymore”saidMr.CharlesMacLeanwhorunsthenation’sbusiestroad．“Wehaverushperiodsandtheykeepgettinglongerandlonger．”

MacLeanwasdescribingChicago’s235milesofexpressway．ButthesamemightbesaidaboutalmostanyoftheexpresswaysthathavebecomeanimportantpartofAmericancitylife—andabouttheheavytrafficthatoftenblocksthem．InChicagoacomputerizedsystemhasbeendevelopedthatcontrolstrafficonthecity’ssevenexpressways．Nowoneman—acontroller—canfollowthemovementofChicago’strafficbylookingatasetoflights．Thesystemuseselectronicsensorsthatarebuiltintoeachexpresswayhalfamileapart．Severaltimesasecondthecomputerreceivesinformationfromeachsensorandtranslatesitintogreenyelloworredlightsonamapinthecontrolroom．Agreenlightmeansthetrafficismovingforty-fivemilesanhouryellowmeansthirtytoforty-fivemilesanhourandredmeansheavy traffic—carsstandingstillormovinglessthanthirtymilesanhour．

“SeethatredlightnearAustinAvenue?”thecontrolleraskedavisitor．“That’sarepairtruckfixingtheroadandthetraffichastogoaroundit”．

AttheRooseveltRoadentrancetotheexpresswaythelightkeptchangingfromgreentoredandbacktogreenagain．“Alotoftrucksgetontheexpresswaythere”thecontrollerexplained．“Theycan’tspeedupasfastascars．”

Thesensorsshowimmediatelywhereanaccidentorastoppedcarisblockingtrafficandatruckissentbyradiotocleartheroad．Thesystemhasloweredthenumberofaccidentsby18percent．Therearenow1．4deathsonChicago’sexpresswaysforeachonehundredmillionmilestraveledwhileinotherpartsofthecountrythereare26．

TrafficexpertssaythattheChicagosystemisthe“comingthing”．SystemslikeChicago’sarealreadyinuseonsomeexpresswaysinLosAngelesandHouston．“Chicagohastakenthelead”saysNewYorkCity’strafficdirector;andheadds“Wearefarbehind…”

1．HowdoesthecontrollerfollowChicago’straffic?

A．Bycontrollingthetrafficlights．

B．Byoperatingacomputerinthecontrolroom．

C．Bysendingatrucktocleartheroads．

D．Bylookingatasetoflightsonthemapinthecontrolroom．

2．Theunderlin