OPINION Every day a river of cars flows across the Bay Bridge into San Francisco, bringing workers, tourists, and visitors to the city. Nearly all run on petroleum fuels. Every day a staccato procession of planes lands at SFO, bringing tourists, conventioneers, and returning residents. All fly on petroleum fuels. Every day a phalanx of trucks delivers food to grocery stores, restaurants, and corner markets. All run on petroleum fuels. Every day roads are paved, potholes are filled, roofs are tarred, machinery is lubricated, and tires are replaced. All are done with petroleum-derived products. Read more »