September 22, 2014
FRESNO, Calif. (AP) - Safety experts are bracing for the two foggiest months of the year in California's San Joaquin Valley and hoping an intricate warning system continues to keep drivers safe.
Areas along Highway 99 south of Fresno are notorious for dense tule fog, a thick patchwork that materializes after rain an average of 35 days a year.
The sudden transition from sun to fog often catches drivers by surprise.
In 2007 a 108-vehicle pileup killed two people and closed 99 for half the day. Officials began planning then for a fog warning system along the highway's most dangerous 12 mile stretch south of Fresno.
Since 2010 Caltrans has operated six weather stations, 12 cameras, 39 electronic message signs and 41 microwave sensors that automatically warn drivers when conditions become dangerous.
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