That's why I said I couldn't imagine anyone actually using them. Besides that, the astronauts would have had to get out of the Apollo capsule and somehow get over to the cables with their suit on. However, the guys who worked there at the pad told me that the man that designed those escape cables did slid down them so it could be done.
I should think that the terminus would be elevated such that, with planning, you could account for the weight of a rider and the line and, with some slack, the rider would actually begin to climb a little as he reached the end of the slide. That should slow him down enough that he could simply let go and drop a few feet into a PLF (parachute landing/fall) when the he neared the end of the ride.