As you know, two of the reactors in Fukushima Nuclear Power Plant have exploded due to meltdown, and the actual demand of electricity greatly exceeds the overall supply capacity without nuclear. Thus scheduled blackout will be conducted in Tokyo today, and the first blackout will start soon in next 10 minutes.
This blackout is carried out in turn on 5 groups. The group number will be assigned for each small districts in the city. My house is in Group #5 district, and the blackout starts today from #5 districts and lasts for 3 hours. I'm really not sure what will happen when it get dark.
Also the public transportation is out of service due to this scheduled power outage. Actually, it was scheduled first from 6 o'clock in the morning, but the demand didn't exceed the supply capacity, so that it was postponed till now. The blackout effects millions of people and those include some disabled people such as who require mechanical ventilator and other medical equipments to keep their lives.
Hope it will be done safely...