just tell the trainer (if one of you is driving), that you NEED to stop. if already parked for the 10 hour break, just go do your business. can't really hold it in, it's not healthy.
Let er rip tater chip!! I saw a blonde woman (4 wheeler) take a squat on the side of the road on i84 one time, broad daylight, and she wasnt even covered up that good next to her suv.. im guess she really had to go, i got me a good look at her bare butt as i went by and caught me another look when she passed me in the hammer lane about 3 or 4 miles down the road, she was a looker for sure!!
We had a lady water truck driver, the water truck stayed hooked up in the recycle train all day, so she had to sneak off or get someone to relive her and catch a ride in the pilot car to the can up the road. You would have to seen her to belive it, but this gal would have field dressed 450 or better, were talking huge. I had to pull up a for or so and when I started off the clutch, I heard a scream, she had squatted between my drives and the sleeper to take care of business. I clutched it and looked in the mirror, and got a sight that bleach wouldn't take away.
Wife used a fluff jar when we were driving (easier for a woman to target). I preferred the 1 liter bottles with the larger opening to pee into. If your bashful just turn your back to the one sleeping.