I've calculated that I spent about $37,500,000.00 on used cars in my lifetime, as I'm co-owner of a classic car dealership in Southern California. The only time I do not use cash is when I buy a car that's too far away to look at, in which case I do a bank wire transfer. That's as safe as it get. Otherwise, cash is king, always, and almost all sellers want cash, and cash only. Since I have often up to $100,000 cash on me, I also carry a concealed firearm.
If the car you are buying is rather expensive, and you do not feel comfortable to have a large amount of cash on you, you could also suggest to meet at your bank and have them issue him a cashier's check in his presence.