LOS ANGELES — California’s highways aren’t as smart as they used to be.
Buried under thousands of miles of pavement are 27,000 traffic sensors that are supposed to help troubleshoot both daily commutes and long-term maintenance needs on some of the nation’s most heavily used and congested roadways. And about 9,000 of them do not work.
The sensors are a key part of the “intelligent transportation” system designed, for example, to detect the congestion that quickly builds before crews can get out to clear an accident.
A speedy response matters: Every minute a lane is blocked during rush hour means about four extra minutes of traffic. Fewer sensors can mean slower response times. So the fact that 34 percent are off-line — up from 26 percent in 2009 — creates an extra headache in California’s already-sickly traffic situation.
“(It) is not an acceptable number, really,” said California’s top transportation official, Brian Kelly.
With limited space and money for new lanes, Kelly said, maximizing flow on existing freeways is critical. To do so, planners rely on a network of cameras, above-road detectors, message boards and the in-road sensors called “loops” because of their shape.
Some loops were cut during construction, others yanked out by copper wire thieves. Many have succumbed to old age.
The resulting blind spots show up as strings of gray amid the green, yellow or red on the large map that freeway managers overseeing Los Angeles and Ventura counties monitor for signs of trouble. Even worse off than Los Angeles are inland areas such as the San Joaquin Valley and San Bernardino and Riverside counties.
The outages are significant enough that the sensors alone cannot produce real-time traffic maps that are useful to the public, especially when compared with the many private traffic mapping services that drivers rely on to get around.
In the Fresno and San Francisco Bay areas alone, Caltrans plans to spend $35 million to fix loop sensors — as well as freeway lights, cameras, ramp meters and other electrical systems — that are down due to metal scavengers or other problems.
The state that pioneered the use of loop sensors starting in the 1970s is not alone in its struggle to keep them producing reliable data. In Utah, transportation officials estimated about 20 percent of loops do not work.
About 75 percent of loops in the Austin, Texas, area are not working due to large-scale freeway resurfacing.
Michigan’s transportation planners abandoned loops because they found too many failed during winter’s freeze-thaw cycle.
