The land ministry has officially announced a transportation plan, named "operation eight directions," to be used in the event of an earthquake with a seismic centre directly beneath the Tokyo metropolitan area.
The plan will secure emergency routes in eight directions toward central Tokyo within 48 hours of the occurrence of such a quake.
By linking expressways and main roads that have suffered less damage, the Land, Infrastructure, Transport and Tourism Ministry aims to open roads into the devastated centre of Tokyo at the earliest opportunity, to assist rescue workers and for the transportation of necessities.
The plan was mapped out by the ministry in July last year, with the details having been under discussion with the National Police Agency and other entities.
According to the ministry, about 7,300 vehicles would be stranded on the roads inside Tokyo's 23 wards, if an earthquake measuring maximum 7 on the Japanese seismic intensity scale of 7 directly hit Tokyo with most of the 23-ward areas jolted at an intensity of lower 6 or more.
Debris would also be scattered on the roads, and about 30 bridges would develop uneven surfaces due to liquefaction or other factors.
Based on these assumptions, the plan lists in advance roads leading to central Tokyo from eight directions, so that materials such as sandbags and iron plates can be stocked along the route in each direction.
In an emergency situation, the best combination of roads would be selected, so that a large number of workers as well as equipment and trucks could be deployed to secure necessary routes.
For example, 25 dump trucks and 82 workers will be deployed to secure at least one lane in each direction, around the Tamagawa Ohashi bridge on National Highway Route 1.
The plan also stipulates the removal of stranded cars from roads without owners' consent based on the revised Basic Law on Natural Disasters, which was enacted in November last year.
It aims at establishing a system of rescue within the first 72 hours of a disaster, which is crucial for survivors who are buried under debris.