Air quality officials issued a Spare the Air advisory for today, saying hot stagnant weather would contribute to increased levels of ozone.
It is the 11th such day this year - the most of any year since 1999 - for which officials have urged Bay Area residents to limit their driving and use public transportation.
For the first six of those days this year, public transit offered free rides to encourage use.
But that program, which cost about $13 million and drew more than a million people into the region's public transit system, has ended for the year, said Luna Salaver, a Bay Area Air Quality ManagementDistrict spokeswoman.
She said ridership on Santa Rosa CityBus increased between 8 percent, or 696 riders, and 19 percent, or 1,418 riders, for each of the six days when free fares were offered.
On the Golden Gate bus service, ridership increased from 10 percent, or 2,622 people, to 20 percent, or 4,829 people, on the six free days, Salaver said.
A high temperature of 90 degrees is expected in Santa Rosa today, according to the National Weather Service.
High ozone levels are particularly harmful for young children, the elderly and those with respiratory and heart conditions.
- Jeremy Hay
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