If you are the driver, you are in control and can decide when to take breaks. So all is fine, as long you don’t get too carried away by your favorite music and forget to stick to your bathroom schedule. If you are the passenger, prepare the driver in advance about your need for breaks. If it is someone who doesn’t know about your bladder issues, it might be good to tell them, that you need to go, when you need to go (not necessarily when the car needs to be filled anyway). Just say you need to use the restroom at fixed times – no more explanation is required. Use the Wheelmate app to locate the nearest restrooms on your trip.
Some buses have a tiny restroom onboard (usually involving stairs). If this is inconvenient for you, ask the bus company in advance when the planned breaks are, so you can see if you can make it fit with your own catheterization schedule. You can also consider to bring a catheter and bag solution, enabling you to catheterize on the bus. Pack a blanket as well for privacy.