First of all....tell him YOU'RE the one who is going to have use of the car on a regular basis, and see his reaction. Oftentimes, the working parent assumes that the non-working parent doesn't need a car, so it's too easy to give up that second car. Yes, bills need to be paid, but it should be a discussion. Not a..."I sold my truck, and we're using the money to pay off some bills."
Otherwise, we've only ever had one car (3 1/2 years of marriage and a 3 year courtship) and right now we have no car. The no car works here, because of the public transportation. The one car worked in the past, because it just did.
Yeah...emergencies happen, but they're emergencies, and having a car doesn't necessarily fix that. For example, DH took our one car to work with him, when I was pregnant. If I had gone into labor, I would have been in labor and it would have been very unlikely that I would have wanted to drive myself anywhere. I had friends (or at least acquaintances) who I could have called and they could have gotten me where I needed to go (people are usually pretty good in emergency situations) if DH wasn't available. If that didn't work, I could have called a cab. If that didn't work, I could have called an ambulance.
It's completely manageable as long as you communicate your needs.
As far as Saturdays go....I have 5 siblings. Even when my parents had 4 cars, I still ended up waiting around places, until I could drive myself. Yeah it sucks, but if you prepare for it, waiting can be rather productive.