The Vacaville branch originally connected to the main line at Creed via a wye; when the air base expanded during WWII, that line was removed and replaced by the line to Dozier--with another wye. When the connection to the SP was built (to replace the line severed by the ship channel), it included a wye so a train could head to either Vacaville or Dozier. On the other side of the bridge over the SP was a wye at the junction with the Willota branch. I believe the spur into the air base during WWII had a wye also. Way back when, there was also a wye in Fairfield where the Suisun City branch took off from the Willota branch. So that's "only" six wyes on the SN in Solano County.
Now, who remembers when downtown Vacaville reeked of onions?