As a motorcyclist who rode a lot of country roads, when one of us had to pee, we'd park our bikes together at the side of the road. The rider in distress would cross the road and get on with business as hidden as possible, while the other stood guard across the road. If a car came into sight, it was that rider's responsibility to do jumping jacks. They always look at the one doing jumping jacks. If they suspect anything, they look behind the one doing jumping jacks.

Try it. Or perfect the Pro Peloton Piss maneuver. It's like the Spanish Inquisition. No one expects it.