The following PDF is a Safety Alert issued on August 19, 2013 which discusses the potential safety hazards associated with using runways as taxiways.
Two main hazards were found. Briefly described below. For the full description and recommendations, read the SAFO (PDF).
A common Air Traffic Control (ATC) practice lately is to utilize an active or inactive runway as a taxiway due to airport geometry, construction, congestion, or taxiway restrictions which can increase risk as signage is spread further apart and sometimes difficult to read from the cockpit. An additional hazard is the intersections of runway-to-runway crossing points are frequently missing many of the visual cues present on taxiways such as signs, markings, and lighting. Find out about this Safety Alert and the recommendations to mitigate at your facility.