I don't like to use the toilets on moving vehicles: trains, planes, buses, boats, ferries. So I don't. Instead I'll just hang on for as long as I can.
I don't have a fear of them, I don't come out in a hot sweat or panic attack I just find the whole concept of weeing and moving quite strange.
Toilets in moving vehicles are often filthy and disgusting anyway, which is another reason to avoid using them.
If I get desperate and I'm nearly beyond control then I'll use them, but I'll hang on for as long as humanly possible.
Today I did a 4hr train journey without going.