Wearing adult diapers on a road trip makes for a more comfortable road trip as you do not need to stop to use the restroom and can just pee in your diapers.
I would recommend thick adult diapers that are plastic backed for road trips.
The diapers I wear on road trips are Northshore Megamax diapers or Abu Super Dry Kids diapers.
I also sometimes wear Attends Poly backed diapers if it's a shorter road trip but for longer road trips I wear the thicker diapers.
Bambinodiapers are also good for road trips and they are plastic backed as well.
In my experience plastic backed adult diapers are much better than cloth backed diapers.
With cloth like cloth backed adult diapers they use Velcro to secure the diaper and I find that those diapers sag more because I cannot get a good fit around the waist with those.
With plastic backed adult disposable diapers they use regular tape with a landing zone which sticks much better and allows me to get a tighter fit.
Cloth liked disposable diapers also seem to leak urine through to the outside for some reason while the plastic backed adult disposable diapers do not.
The plastic backed adult diapers usually hold more urine as well and are much more comfortable especially for extended wear.
Attends Poly backed adult diapers are good for a cheap disposable adult diaper but if you want thicker ones then try Northshore Megamax diapers or ABU super dry kids or any of their other adult diapers.
Bambinodiapers.com also has good thick adult sized disposable diapers that are plastic backed as well.