The main problem, however, was congestion rather than destruction. Because everyone was trying to call at the same time, nobody got through. Networks are designed to handle about ten percent of their subscribers at one time. Next day, network demand was still 20 times normal peak. This is not a short-term problem for disaster areas.
Experience shows that after a crisis the volume of calls stays heavy for a long time.
In Kobe, as before in California, most incoming long-distance calls were blocked in favor of outgoing calls. Mobile communications proved helpful in bypassing destroyed landlines. But they, too, were vulnerable and congested. Traffic volume was seven times normal. In heavily damaged areas, one third of NTT's transmission towers were damaged or stopped working for lack of electricity.