MerlinE~
I disagree with nothing you say, however, if you are out riding and a thunderstorm occurs, unless you get inside at a stranger's home, you are equally exposed moving or stopping.
In the out in an open field scenario, people think they should cower in a ditch. Ditches usually contain water, and have a higher exposure risk from ground currents.
People think trees provide cover, but a lightning tree strike is a bad thing. Sap and water boil and the tree explodes. In hiking, secondary damage and ground currents cause similar damage as direct strikes.
My opinion would be keep moving, avoid hill crests, and get out of the weather. Stopping under an overpass is safer than being in the open, but things can still happen there (ground currents).