A long route 90 near San Antonio, brake lights are starting to flash. Twenty-five kilometers away, Sam Mendoza is sipping coffee in the region's "TransGuide" traffic management center,where 16 wall-mounted television monitors display scenes from some of the 109 video cameras peering at 100 kilometers of area highways. Suddenly, a beeping sound signals that traffic on Route 90 has slowed below 40 kilometers per hour, as sensed by some of the 1,700-odd magnetic-loop detectors embedded in the region's roads.Mendoza seizes a computer mouse and zooms a highway-mounted camera toward the problem spot; soon his monitor reveals two bearded men in the breakdown lane struggling to fix a pickup truck's flat tire.He quickly types a keyboard command, causing an arrow on an electronic sign hanging over the righthand
lane to flash from green to yellow. The light warns drivers about the flat-fixers, hopefully allowing them to avoid an accident or maybe find a different route.

At first blush, the system at Mendoza's disposal sure looks like a smart way to fight traffic. That's what the federal government thought a decade ago when it began funding "intelligent highways," a snappy term for a laborious program of installing sensors, video cameras and programmable signs along the nation's highways. Today, systems in place in San Antonio and 49 other urban areas are indeed providing speedier accident response. But the cost is mounting, with the total taxpayer tab topping $8.5 billion to date. And despite that investment, controllers can't detect traffic beyond where the sensors are installed. Worse, they have limited ways of alerting drivers; typically it's either via signs or by notifying the news media. And as any
driver knows, even a 10-minute delay until the news breaks on the radio often means it's too late to avoid the snarl.