Making Freeways Work

An Eye on the Fast Lane: Making Freeways Work B Y P R AV I N V A R A I YA B E F O R E L E AV I N G for work you can check the weather from the newspaper, radio, or TV report. You can just look at the sky and make your own guess. But you can’t d e t e rmine much about current traffic conditions. TV and radio traffic re p o rts provide only a summary (“traffic is running smoothly this morning”) and spotty coverage of incidents (“an accident in the second lane has been cleared”). If you are unexpect- e d l y stalled in traffic, your frustration and anxiety mount. You don’t know how long you’ll be stuck or whether you should use your cell phone to cancel your appointment. You need a service that tells how long you can expect your journey to take if you leave right now or wait for fifteen minutes. You’d love to have this information available on the web, w h e re you could collect if from your computer at home or work or even from your car phone. The service is not available for you today; but it will be very soon. A Berkeley group, in coop- eration with Caltrans and the California PATH program, has developed a prototype computer system that provides this ser vice for Orange County; the plan is to extend coverage to all fre e- ways in California within the year. And the system, called PeMS (Perf o rmance Management System), can do much more than just calculate your trip time. Until now, there has been no way of knowing how efficiently the freeway system is oper- ating. But with PeMS, traffic engineers can analyze whether control equipment (such as ramp metering) is being used effectively and can then adjust settings accord i n g l y. They can track the most frequently congested freeway segments. They can quickly determine the effects ➢ P r a v i n Va r a i y a i s p r o f e s s o r o f e l e c t r i c a l e n g i n e e r i n g a n d c o m p u t e r s c i e n c e , U n i v e r s i t y o f C a l i f o r n i a , B e r k e l e y, C A 9 4 7 2 0 ( v a r a i y a @ e e c s . b e r k e l e y. e d u ) A C C E S S