Is a carpool incentive available to you?
Someone showed me a pretty strong incentive from Contra Costa Transportation Authority (north of Berkeley): by agreeing to carpool twice a week for 8 weeks, each person is receiving gift cards worth $60 to pay for the gasoline.
Check out what’s available to you in your area.
My husband works for the state of Oregon. He doesn’t carpool, but he rides his bike to work every day and thus qualifies for carpool benefits. He gets a special ticket that he can put on his car mirror, if he needs to drive to work, allowing him to park at one of the expensive, limited time meters ringing the state buildings twice a month. He never uses it. He also avoids the expense of a close-to-work parking spot in the state parking lots. I’m saying this from memory, but I think it costs $60/month. There are also special designated parking spots on the street, close to the state buildings, that are designated carpool spots. There may be other benefits of which I’m unaware. My husband isn’t available to ask right now.