There are 27,000 traffic sensors buried under thousands of miles of L.A. pavement. They're part of the "intelligent transportation" system designed to fix both daily commutes and long-term maintenance needs.
Of the 27,000 sensors, a new report shows that 9,000 of them aren't working.
For example, the sensors are supposed to detect the congestion that quickly builds before crews can get out and 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 offline - up from 26 percent in 2009 - creates an extra headache in California's already-sickly traffic situation.
Most of the malfunctions are being blamed on old equipment or construction. Others have been yanked out by copper wire thieves.
California's top transportation official, Brian Kelly, says the numbers are not acceptable.
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.
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 L.A., according to Caltrans, 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 to the many private traffic mapping services that drivers rely on to get around.
So, to post online traffic maps that are ready for public consumption, California and other states are paying the private sector.
California's tab is not large - Caltrans estimates it at $25,000 per year for its public-facing Quickmap - but other states are giving away sensor data and buying back reliable maps as well.
Michigan's transportation department said it pays Inrix Inc. about $400,000 annually for data to populate its Mi Drive map.
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, according to the state department of transportation.
Michigan's transportation planners abandoned loops because they found too many failed during winter's freeze-thaw cycle; they've moved to above-road sensors that use microwaves to detect traffic.
The Associated Press contributed to this report.