Extremely heavy rain once in five years would block access to key roadways, increasing the number of seriously ill patients unable to reach major medical facilities within one hour by 2.27 million, according to a government scenario.

The scenario, prepared by the Land, Infrastructure and Transport Ministry and released Sunday, shows that under restrictions imposed to deal with extremely heavy rain, some 1.48 million people would be stranded.

It was the first time that the ministry has made a projection to assess the potential impact of such road traffic regulations mainly for roads not fully developed in mountainous areas, ministry officials said.

The ministry plans to take the projections into consideration when it compiles a five-year road renovation program by identifying roads that need to be strengthened to prevent landslides or that should be protected, the officials said.

Under the current network of expressways and other major roads, about 7.28 million people, or 6 percent of the population, are outside the one-hour range of major medical centers in prefectural capitals and other large cities.

If heavy downpours strike once every five years, the officials said, 1,444 zones will be subject to road restrictions, and an additional 2.27 million people will not be able to receive medical treatment.

The officials said the number of people unable to receive such high-level emergency medical treatment due to road restrictions would total 1.33 million if such heavy rain hits once a year and climb to 2.54 million if once every 10 years.

The number of "totally stranded" people, defined as residents inside the restricted zones or sandwiched between such zones, would total 670,000 if heavy rain hit once a year, 1.48 million if it came once in five years, and 1.7 million if once in 10 years, according to the ministry projections.