Transportation numbers for San Francisco
According to the US Census Bureau, the transportation numbers for San Francisco didn't change much between the 2000 Census and 2005.
We can compare the 2005 numbers with the 2000 numbers in the "San Francisco County Transportation Authority's Countywide Transportation Plan" of July, 2004. The SFCTA cites the 2000 Census numbers as it compares the "Commute Mode of San Francisco Residents, 1990-2000" on page 40 of that document. In 2000 10.8% of city residents carpooled to work, while that number in 2005 dipped to 8%. In 2000 31.1% of city residents rode transit to work, while in 2005 33% did. The 2000 Census showed that 1.9% of city residents commute by bicycle, and the 2005 numbers say that number is up to only 2% in the intervening five years, making the SF Bicycle Coalition's goal of 10% by 2010 highly unlikely.
Other numbers we should keep in mind: There were 460,150 motor vehicles registered in San Francisco as of January 1, 2007: 378,576 automobiles, 63,438 trucks, and 18,136 motorcycles/motorbikes.
According to the "San Francisco Transportation Fact Sheet" put out by the Municipal Transportation Agency in March, 2006, 261,181 "non-residents" commute into the city every weekday, though it doesn't break it down by which "mode" of transportation these people use. MTA notes that the "total daytime increase in vehicles" in the city is 35,400 on "a typical work day," with 20,000 of those coming over the Bay Bridge and 13,100 coming over the Golden Gate Bridge.
Muni had 685,000 "boardings" on an average weekday in 2004/2005, with 461,491 boardings on an average Saturday and 375,291 boardings on Sundays.
According to the SF Visitors Bureau, the city had 15.7 million visitors in 2005, and they spent $7.3 billion in local businesses, with $418 million in tax and fee revenue going to city government. 4.5 million people stayed in city hotels in 2005, generating $179 million in hotel tax revenue for city government. Of those 4.5 million people staying in city hotels, 25.8% rented cars, which means 1,125,000 rental cars driving into SF in 2005 alone.
We can draw at least one conclusion from these numbers: Redesigning city streets---taking away street parking and traffic lanes to make bike lanes---on behalf of the 2% of the population who ride bikes would foolishly make traffic in the city unnecessarily worse and probably damage our important tourist economy.