One evolutionary branch of the Big Dog family is Alpha Dog, which eventually becomes LS3 (AKA Legged Squad Support System).  Here we start to see the transition from a very rough research prototype to a more polished prototype that is capable of participating in field trials with end users.

First we start in the lab, with a video of Alpha Dog being put through its paces.  One subtle but informative aspect of this video is the safety features associated with the test area: caution tape to warn humans that they are entering a potentially dangerous area, flashing lights on the robot to indicate that it is in operation and may move unexpectedly, and a heavy gantry to prevent the robot from falling over or exiting the test area in the event of a severe malfunction.  Other interesting points to note here are (obviously) the robot’s ability to traverse rough terrain, its impressive “standing up” behavior, and the looting of the Boston Dynamics fitness center (presumably not just to simulate the added weight of a payload but also to adjust the center of mass to correct for asymmetry in the weight distribution of drive components):