If you’re flying into San Francisco, San Jose or Oakland I’ve got some advice for you, arrive early. The Bay Area is a sprawling industrial area with quite a few bedroom communities located in the Central Valley. Avoid the afternoon gridlock by flying in as early as possible and leaving the Bay Area before 3 in the afternoon when many workers start hitting the roadway.
Common slowdown points are: 92/880 interchange, 238/580 merge, 580/680 merge in Pleasanton, 580 in Dublin, 580 @ First Street in Livermore through the Altamont Pass, 120/99 merge in Manteca, and almost anything in Modesto.
Traffic backups are normally 3-5 miles long of stop and go traffic. Alternately you can avoid the whole Bay Area mess by flying into Modesto or Fresno or taking Amtrak to a Central Valley location and driving or taking the connector bus from there.
Remember, if you plan to fly out of the Bay Area you’ll want to fly out as late as possible when most of the traffic is heading eastbound.
To stay up to date with traffic in the Bay Area and into the Central Valley click on the Google Map above (or here) and then Traffic for up to the minute traffic conditions.