If it looks like it may be a rainy day, wear clean jeans. Otherwise you may end up riding in a vehicle and smelling like a wet dog. This is particularly bad if you dislike dogs. I don’t know of anyone who wakes up in the morning and chooses eau de parfum lacher chien mouille* for their scent of the day.
Although… maybe the most extreme dog-lover would be comforted by that aroma.
Oh, and should the above circumstance ever happen to befall you, your best bet is to go ahead and comment on the smell yourself so the other occupants of the vehicle don’t have to wonder. You’ll be much more comfortable for the remainder of the ride. Unless you’re riding with the Pope – or Queen Victoria. If you were riding with Queen Victoria, you would have bigger problems to worry about than the smell of your clothing.
And maybe you shouldn’t mention it to the Pope either. Think of a more important topic to bring up with him. Or don’t ride with him at all.
*The iGoogle translator won’t completely translate that for you, but literally it means “water with perfume of wet dog.”