2 day trip from Texas to Arizona on a greyhound bus. It was the first time I got out of the state. I had to be out in a straight jacket when I found out there was a whole world outside of Texas. I've never knew anything else.
My longest road trip was just a whole day through Scottish Highland. Nothing exciting.
The most painful trip I experienced was 18 hrs (it was horribly delayed) on train from Chiang Mai to Bangkok and then extra 3 hrs on coach to Rayong. All of us literally died at the destination. My earwax was totally blackened by the smoke after the trip.