When I am driving I routinely check my rearview mirror and assess the following distance of the cars behind me, so I usually know I will not be rear-ended when I am stopping for pedestrians or for any other reason. If I am driving and I notice someone is following too close for our speed I will tap the brake lights so as to encourage them to increase their following distance. If this fails I will slow down to a speed where their following distance becomes appropriate. If they are an uncommonly aggressive driver I might even pull over or change lanes and allow them to pass, I certainly don't want to be rear-ended! That said, even if I were to fail at this, I would prefer to be rear-ended stopping for a pedestrian that would have stopped than to strike a pedestrian who failed to stop walking into the path of my vehicle.

The speed limit is a reference to the maximum allowable speed of the roadway, not the minimum, only, or even recommended speed.