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　　“There were no rush hours any more,”said Charles M．McLean, who runs the nation's busiest road．“We have rush periods, and they keep getting longer and longer．”

　　McLean was describing Chicago's 235 mi1es of expressway．But the same might be said about almost any of the expressways that have become an important part of American city life－and about the heavy traffic that often blocks them．

　　In Chicago, a computerized system has been developed that controls traffic on the city's seven expressways．Now one man-a controller-can follow the movement of Chicago's traffic by looking at a set of lights．

　　The system uses electronic sensors that are built into each expressway, half a mile apart．Several times a second, the computer receives information from each sensor and translates it into green, yellow, or red lights on a map in the control room．

　　A green light means traffic is moving forty-five miles an hour, yellow means thirty to forty-five miles an hour, and red means heavy traffic－cars standing still or moving less than thirty miles an hour．

　　“See that red light near Austin Avenue?”the controller asked a visitor．“That's a repair truck fixing the road, and the traffic has to go around it．”

　　At the Roosevelt Road entrance to the expressway, the light kept changing from green to red and back to green again．“A lot of trucks get on the expressway there,”the controller explained．“They can't speed up as fast as cars．”

　　The sensors show immediately where an accident or a stopped car is blocking traffic, and a truck is sent by radio to clear the road．The system has lowered the number of accidents by l8 percent．There are now 1.4 deaths on Chicago's expressways for each one hundred million miles traveled, while in other parts of the country there are 2.6．

　　Traffic experts say that the Chicago system is the“coming thing”．Systems like Chicago's are already in use on some expressways in Los Angeles and Houston．“Chicago has taken the lead,”says New York City's traffic director, and he adds,“We are far behind…!”

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Multitasking

　　People who multitask all the time may be the worst at doing two things at once, a new research suggests．The findings, based on performances and self-evaluation by about 275 college students, indicate that many people multitask not out of a desire to increase productivity, but because they are easily distracted(分心)and can't focus on one activity．And “those people turn out to be the worst at handling different things,” said David Sanbonmatsu, a psychologist at the University of Utah．

　　Sanbonmatsu and his colleagues gave the students a set of tests and asked them to report how often they multitasked, how good they thought they were at it, and how sensation-seeking(寻求刺激)or imperative(冲动) they were．They then evaluated the participants' multitasking ability with a tricky mental task that required the students to do simple mathematical calculations while remembering a set of letters．

　　Not surprisingly, the scientists said, most people thought they were better than average at multitasking, and those who thought they were better at it were more likely to report using a cellphone while driving or viewing multiple kinds of media at once．But those who frequently deal with many things at the same time were found to perform the worst at the actual multitasking test．They also were more likely to admit to sensation-seeking and impulsive behavior, which connects with how easily people get bored and distracted．

　　“People multitask not because it's going to lead to greater productivity, but because they're distractible, and they get sucked into things that are not as important．” Sanbonmatsu said．

　　Adam Gazzaley, a researcher at the University of California, San Francisco, who was not a member of the research group, said one limitation of the study was that it couldn't find out whether people who start out less focused toward multitasking or whether people's recognizing and understanding abilities change as a result of multitasking．

　　The findings do suggest, however, why the sensation-seeker who multitask the most may enjoy risky distracted driving．“People who are multitasking are generally less sensitive to risky situations．” said Paul Atchley, another researcher not in the group．“This may partly explain why people go in for these situations even though they're dangerous．”

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