Fears of unbearable heat this summer for train commuters in the Tokyo Metropolitan Area are mounting for two reasons: (1) Electric power shortages triggered by the accidents at the Fukushima No. 1 nuclear power station may force East Japan Railway Co. (JR East), the major operator of commuter trains, to suspend the use of air conditioners; and (2) with the train cars now in use, windows can be opened only partially to let in fresh air even when the air conditioning is off.

An expert in railway technologies has pointed out that designers of today's commuter trains did not take into account the possibility of air-conditioning cuts to conserve electricity.

Most JR East commuter trains were designed on the assumption that the inside car temperature would always be controlled by air conditioning. Few windows can be opened manually; in fact, the newer windows no longer have curtains and are fitted instead with glass panes to absorb heat rays.