To change my adult diaper on road trips I just stick carry diapers in a laptop bag and take my laptop bag with me into a bathroom at a rest stop or gas station and then change the diaper by backing up to a stall or wall and then putting the diaper between my legs and pulling the diaper up between my legs to change it.
My parents never made me wear diapers on a road trip as a kid but I wished they did.
However I still wore diapers on road trips under my pants without my parents knowing and now as an adult I still wear diapers on road trips.
Wearing diapers on road trips is a good thing so you can pee or poop and not have to hold in the pee and wait for a toilet.
Wearing the diaper on road trips makes the road trip more comfortable and enjoyable as well.
When I have kids though I'm gonna make them wear diapers on road trips and all the time.
When on road trips in the summer the kids I have are gonna wear diapers without pants and wear just a diaper, socks and shirt and shoes and be dressed like the boy below.
More pictures of him at the link below.