Yes it is a good idea for an adult to wear adult diapers on a road trip.
Actually it's a great idea to wear adult diapers on a road trip because it means you can pee and even poop in the diaper while driving or riding in the vehicle without needing to stop.
When wearing adult diapers on the road trip there's no need to stop as often and you don't have to wait in line for a toilet.
I've been on road trips without diapers and had to pee really bad and when I got to the restroom someone was already in the restroom or the restroom was closed.
And then I nearly peed my pants.
So now that I wear diapers on a road trip and wear them full time I just pee whenever I feel the urge and then change the diaper later.
I've been wearing diapers again full time now for almost 9 years and will never stop wearing diapers as long as I live.
Diapers are fantastic for road trips and anytime else.
Kids including older kids and teens should also wear diapers while on road trips so they do not have to hold in their pee and they can change the diaper later.