When a group of motorcyclists is overtaking another vehicle on a two-lane road, it is crucial to do so one rider at a time. This method ensures each motorcyclist has ample space and visibility, minimizing the risk of accidents due to inadequate clearance or unexpected movements by other vehicles. It allows each rider to assess traffic conditions accurately, complete the maneuver safely, and then create space for the next rider to proceed, maintaining group cohesion without compromising safety.