Caltrans is going high-tech this winter in its battle against ice and snow on the Antelope Valley Freeway, a highway used by more than 40,000 Los Angeles area-bound commuters daily that has been forced to close during snowstorms.
A computerized system that relies on road sensors and small, roadside weather stations is being installed in two places along the freeway, the primary route between the Antelope and San Fernando valleys.
The sensors and weather stations will be located near the Avenue D (California 138) off-ramp north of Lancaster and in the area of the Angeles Forest Highway-Pearblossom Highway exit south of Palmdale.
The $280,000 project also calls for installation of two other weather stations and sensor groups, one on the eastern end of State 138, an east-west route that cuts through the north Los Angeles County region, and the other at State 138 and the Golden State Freeway.
"It's quite a fantastic system," said Tom Pellerin of the California Department of Transportation.
The system--known as SCAN, short for surface condition analyzer--is expected to be operational in December, said Pellerin, maintenance supervisor for the system in the Antelope Valley. It is about 80% installed.
The system is able to provide officials with information on pavement temperature, air temperature and relative humidity. It also can detect whether a road is wet or dry and if frost, ice, snow--or even chemicals such as ice-melting salts--are present, said Lee Benjamin, Caltrans maintenance supervisor at the agency's Lebec station.
In 1990, Caltrans installed a SCAN system along a 25-mile stretch of the Golden State Freeway in a mountainous area north of the Santa Clarita Valley.
Benjamin, whose office receives the data from the Golden State Freeway sensors, said SCAN has worked well in the Grapevine area and that Caltrans is installing the system up and down the state.
The key to the system, he said, is that it provides for better use of resources. Rather than having to drive snowplows and sand spreaders between Whitaker Summit and the Grapevine looking for trouble spots, SCAN pinpoints their locations.
And with its localized weather forecasting, called SCAN Cast--which is updated every eight hours from SCAN manufacturer Surface Systems Inc., based in Missouri--the transportation agency is able to accurately determine if a traffic-disrupting storm is headed toward the region, Benjamin said. This allows for better scheduling of workers and reduced overtime costs.
Furthermore, information garnered from the system enables Caltrans to better know where to lay traction-improving sand and salts, he said.
Pellerin said he will even be able to monitor the Antelope Valley SCAN data from his home computer, helping him determine whether weekend or after-hours road crews need to be called in to clear highways.
Despite all the system's benefits, it cannot prevent road closures. Yet, Benjamin said, it does give Caltrans a jump on conditions so that they often can be improved earlier, enabling roads to stay open longer.
"We're able to work things out to keep traffic flowing," Benjamin said.
In the Antelope Valley, snow and ice are not quite as prevalent as along the Grapevine area of the Golden State Freeway, but they can still cause problems.
In January, 1992, thousands of motorists were unable to return to their Antelope Valley homes when a severe snowstorm forced the closure of all routes into the region. The Antelope Valley Freeway was shut down for eight hours, just as tens of thousands of afternoon rush-hour commuters were heading home.
Once winter passes, Benjamin said, the SCAN system is not given a rest. He uses it, for example, to get road-surface temperatures to determine when to do asphalt work, which must be done at no less than 50 degrees.