Testing done on Saturday November 23, 2013 at 8 AM in front of the EECS Building on the University of Michigan North Campus. The temperature was -2 C (about 29 F). MARLO is an underactuated 3D bipedal robot with passive prosthetic feet. Its feedback control is designed using virtual constraints. In previous experiments, MARLO was attached to a boom. but with improved control, the robot can now walk without any external support. A mobile gantry supports a safety cable to catch the robot when it falls, avoiding expensive and time-consuming repairs. The robot is one of 3 ATRIAS-series robots designed and built by Jonathan Hurst at Oregon State University. The other two copies are at CMU [with H. Geyer] and Oregon State.