Photo/Illutration A cracked slab from the Tatsubagawa bridge in Nagano Prefecture with its corroded reinforcing steel bars is seen on Nov. 15 in Hachioji, Tokyo. (Hirotaka Kojo)

A new national safety assessment has shown that an additional 1.5 trillion yen ($11.54 billion) is needed to repair Japan’s aging expressways.

Anticipating the cost to rise further in the future, the government will submit legislation in the current Diet session to secure the funds for the maintenance work and allow operators to collect highway tolls for an additional 50 years to 2115.

In the safety assessment, three expressway operators in eastern, central and western Japan discovered a total of 500 kilometers of roads that need repair, which will cost about 1 trillion yen, a source familiar with the matter said.

Late last year, the operator in charge of Tokyo’s metropolitan expressway estimated about 300 billion yen is needed to repair some 22 km of its highways, and the company that runs expressways in Osaka and Kobe areas said on Jan. 27 that it needs some 200 billion yen to fix the same length of roads.

Combined, five of the nation’s six highway companies have estimated the additional cost at 1.5 trillion yen.

The other one, which manages expressways connecting the island of Shikoku and the main island of Honshu, said its highways are currently under assessment, but the same source said no additional expense is expected from the company.

Two years after the 2012 deadly accident in the Sasago Tunnel on the Chuo Expressway in Otsuki, Yamanashi Prefecture, where a collapsed ceiling killed nine people, the government ordered operators to assess safety risks of their expressways once every five years.

The completion of the checkup on all routes in the country, stretching for about 10,000 km, revealed the scope of the cost for maintaining the aging infrastructure.

In addition, operators expect to discover more locations in need of repair as drone inspections, ultrasonic testing and other new technologies help detect internal cracks and corrosion previously unknown to engineers.

In 2014, the six operators gave an initial estimate of 4 trillion yen to repair 2,300 km of roads under their jurisdictions, or one-fourth of the entire expressway network.

However, the figure has swollen to 5.4 trillion yen, separate from the 1.5 trillion yen added just recently, due to surging raw material costs, a new 200 billion yen tunnel in Tokyo’s Nihonbashi area and new approaches designed to minimize the impact of roadwork on traffic.

When the Japan Highway Public Corp. was split up and privatized in 2005, the government announced a policy to collect tolls until 2050 to cover the construction costs--and to make the expressways toll-free afterward.

However, the government extended the 2050 deadline on toll collection to 2065 to secure the funds needed to manage the aging expressways. The deadline is expected to be push back once again to 2115 in the current Diet session.