Realizing the fact that 84 key communications facilities, earth stations, Department of Defense voice and data switches, commercial transoceanic cable heads, Federal Telecommunications System switches, and major direct distance dial switches are located within 55 miles of either Los Angeles or San Francisco, damage must be expected to occur. With this realization, priorities have been assigned to all critical circuits transiting the key facilities, based on established criteria of criticality of service continuity. _National warning systems circuitry, command and control circuits, and circuits supporting diplomatic negotiations_ (of which a high concentration exists in California) are examples of those circuits carrying high-restoration priority. In the civil sector there would be 24 to 72 hours of minimal communications, with a possible blackout of telephonic communications in the area immediately following an earthquake. The commercial carriers would institute network control procedures to regain control of the situation as fast as possible. The impact on transportation facilities in any of the four hypothesized earthquakes could be massive. Since the magnitude and severity is unprecedented in recent years, conclusions regarding losses must be accepted as tentative. As in the case of hospitals, however, the lessons learned in earthquakes during the past 10 years are being incorporated in the design and construction of new facilities. In general, all major transportation modes would be affected--_highways_, _streets_, _overpasses and bridges_, _mass transit systems_, _railroads_, _airports_, _pipelines_, and _ocean terminals_, although major variances in losses are expected among the modes. From a purely structural standpoint, the more rigid or elevated systems (such as railroads and pipelines) which cross major faults on an east-west axis would incur the heaviest damage, with initial losses approaching 100 percent. Other major systems (such as highways, airports, and pile-supported piers at water terminals) have better survivability characteristics and therefore would fare much better, with damage generally in the moderate range of 15 to 30 percent. These transportation facility loss estimates are stated in terms of immediate post-quake effects. They do not reflect the impact of priority emergency recovery efforts and expedient alternatives that are available, some within hours, to aid in restoration of transportation capacity. In addition, transportation systems generally have an inherently significant degree of redundancy and flexibility. Consequently, an unquantified but significant movement capability in all transport modes is expected to survive. Finally, these loss estimates do not take into account the question of availability of essential supporting resources, particularly petroleum fuels, electricity, and communications. In the initial response phase, these could prove to be the most limiting factors in the capability of the