] robots compete annually in two international
] search-and-rescue tournaments, measuring their progress
] in diabolically difficult arenas designed by the National
] Institute of Standards and Technology (NIST).
]
] With current technology, negotiating an unstructured
] rubble- and debris-filled environment is about the
] hardest thing there is for a robot to do. That
] researchers even attempt it shows how far robotics has
] come in recent years. That it always fails, and sometimes
] spectacularly, shows how far it still has to go.

It appears that sensors are a limiting factor. Each type of
sensor can be confused or disrupted by some aspect of the
environment.

Search-Rescue Robots Test Their Mettle in Tournaments (TechNews.com)