If a driver doesn't want you on their ride, it's not gonna be because you are costing them gas money (as high as gas prices are these days), it gonna be because they either just don't want you to fuking touch their car, or because they're scared they're gonna hurt you (in which case they really know that an accident wouldn't be their fault, and should know that when they dodge you, they're prob just being more dangerous)
Please, it's not about gas money or being afraid, it's about the fear of someone running out in front of your car, and now having two possible injuries happening. It's about being annoyed that someone you don't know sitting on top of a metal thing that can gouge your paint job about six inches away in moving traffic. It's about that jerk - if he scratches your car - bailing because he
can, and having no recourse.
Here's the thing. If you were to ask, I'd let you, because that's polite and responsible, and I'd feel safe assuming you're cool. When you
other posters when they talk about respect, I don't think you're the type to ask, or to care.