5:30 p.m.Thursday is the second Spare the Air Day in a row, with most Bay Area transit systems offering free rides, including the VINE, the American Canyon Shuttle and the Yountville Shuttle.

Bus systems in Vallejo and Santa Rosa are also free all day. BART and the ferries are free until 1 p.m.

This is the second Spare the Air Day of the summer, following Wednesday’s declaration.

Because of high temperatures and low wind, the air today should be smoggy. People who ride transit are helping reduce pollution.

Participating public transit agencies in the Bay Area include

ACE AC Transit AirBART Alameda/Oakland Ferry Alameda Harbor Bay Ferry American Canyon Transit BART Benicia Breeze Caltrain Cloverdale Transit County Connection

Dumbarton Express Emery Go Round Fairfield/Suisun Transit Golden Gate Ferry and Bus Healdsburg Transit LAVTA/Wheels Marin Transit Muni Petaluma Transit Rio Vista Delta Breeze St. Helena Shuttle

SamTrans Santa Rosa CityBus Sonoma County Transit Tri Delta Transit Union City Transit Vacaville City Coach Vallejo Ferry and Bus VTA VINE Yountville Shuttle WestCAT

Info, www.511.org/sparetheair_2007