Car insurance by the tankful? Not quite, but California moved a step closer last month to pay-as-you-drive policies that could allow motorists to buy insurance like they do gasoline — a little at a time. Insurance Commissioner Steve Poizner released regulations permitting and authorizing mileage verification for pay-as-you-drive, without dictating what form such plans must take. The goal is to use per-mile pricing to entice Californians not to drive so much, thus easing air pollution, relieving traffic congestion and lowering the number of traffic collisions.