The pedestrian crosswalk is when two people are having sex and a third party person walks over or on the backs of the people during intercourse.
This position is best done outside in the streets.
It is believed homeless people invented this sexual position. Either them, or a group of drunk frat boys.
John and Jane had no money for a hotel room so they had sex in the middle of a busy sidewalk and ending up doing it pedestrian crosswalk style.