I love to do this when on a road trip with my wife. She always drives because she drives faster than I do, also, people who drive like assholes piss me off and I have to resist the urge to get "road rage" but it doesn't affect her at all. Also, I tend to get nervous about leaving the house on vacation so, when we leave--to calm my nerves about it--she'll usually hand me a large beer which I drink (very clandestinely, of course) as we drive the first 50-60 miles. By then I'm over the anxiety and all is fine.
And this, of course, is just a perfect time for me to wear my diapers! If my kids aren't around she will put me in thick cloth diapers (usually what I'd wear to bed at night if I slept in them) and off we go. Sometimes we'll put me in cloth diapers and instead of plastic pants, will put a disposable on over them, then, if I get to be soaking wet, we just change the disposable (leaving me in the warm, wet, "inside" cloth diapers).
This works well. She can hold her pee for hours, I'm happily wearing my diapers, so we usually only have to stop every 3-4 hours (and most trips don't even last that long). When we do stop, it's to get gasoline and she will send me out to fill up the car--wearing bulky, drooping, wet diapers under my shorts--while she goes inside to get drinks / snacks and use the restroom. I've gotten a few good looks this way. One of these days I intend to do this wearing only a t-shirt, diapers and plastic pants and no shorts.
Upon arrival, we check into the hotel / motel. By then my diapers are so wet they're about to fall down. It's totally obvious to anyone else in the lobby if they look closely that I'm diapered. And, if there's any doubt, there, in plain sight, on the baggage cart, is my diaper pail.
On one occasion--a ten hour trip that we took--my diapers got so wet that I had to change them in a McDonald's parking lot while she was going inside to pee and get food. While I was doing this, another car pulled up next to ours, a lady got out, looked in the window as I was pinning my diapers back on, and I got a really good look. LOL.
I absolutely love doing this and hope to do lots more of it once my kids finally move out of the house.