I get a glimpse of my passengers when they get in the cab, and occasionally I'll turn around if we're having a conversation, but for the most part the sense that really sticks out is their smell. I had some good ones today.
I picked up a couple Japanese guys at a golf shop in Shirlington and took them to their fancy hotel near the White House, and one of the dudes (the one who was doing most of the talking, unfortunately) had gross breath. Really gross; I had to cover up my nose without making it obvious. I picked up a young woman from an office building in Rosslyn that clearly has its own gym, which she had used, and she stank pretty badly. You know, like lady gym sweat. And finally, I picked up a guy who talked exactly like Ali G and reeked of weed. What a night!