SAN FRANCISCO - The Freeway Service Patrol fleet of roving tow trucks is expanding its territory to cover new segments of the East Bay.

The new segments are along state route 4 in Contra Costa county, state route 29 in Napa and Solano counties, state route 12 in Napa, Solano and Sonoma counties, and interstates 80, 680 and 780 in Solano county, according the Metropolitan Transportation Commission.

The expanded service adds more than 85 miles of coverage, bringing the regionwide network to 530 miles, and adds six trucks to the fleet for a total of 83.

The MTC oversees the FSP in partnership with the California Highway Patrol and Caltrans.

"Half of all the congestion on Bay Area freeways is due to accidents, stalls, debris spills, and other incidents," said Solano county Supervisor Jim Spering, who represents Solano County on MTC's Service Authority for Freeways and Expressways.

The MTC said the fleet's drivers stop more than 11,000 times per month, on average, to clear debris, tag abandoned vehicles, and assist stranded motorists.

The trucks offer basic services such as helping to restart stalled vehicles or changing tires free of charge. The program is funded by federal, state, and local funds, including part of a $1-per-vehicle annual registration fee assessed to Bay Area motorists.