Join Date: Jul 2005
Location: San Francisco Bay Area
For the most part, the road closures are put in place around 20 minutes before the first riders go through. Then they wait for all the support vehicles to pass and then open up a few minutes later. So if there aren't stragglers, you can get through with a vehicle maybe about 10 minutes after the last cyclists pass.
There are some roads that are closed for more extended periods. Sierra Road, for example, was shut down from the morning. But these will be announced.
When the road is closed, no auto traffic is allowed, but people are free to walk the sidewalks/shoulders.