Let's assume that our Apollo astronauts are on the Moon, driving their Lunar Rover and they are far away from the LM. What if LRV failed during the mission? Would they be able to get back to the LM on foot?
The track for the Lunar Rover was planned not to exceed the maximum walking distance back to the LM.
The astronauts could drive away from the LM to the maximum distance and then drive a circle around the LM. Every spot outside this circle was forbidden, any spot inside the circle was allowed. As long as they stayed inside the circle, they were permitted to drive to any unplanned but interesting-looking spot.