Messages from Departments and Centers of NILIM
For the maintenance and renewal of the aging road structures
MORI Nozomu
Director of the Road Department(key word)
1.

Road structure, Aging, Maintenance, Renewal

Recent Movements
In January, 2013, the Social Capital Maintenance
Strategy Subcommittee and the Social Capital
Improvement Council made urgent proposals. They werebased on that the painful accident of sudden ceilingcollapse that occurred in the Chuo Expressway Sasago
tunnel on December 2, 2012, and caught attention raisingpeople's uneasiness that urgent maintenance is necessaryfor the aging social capital.
In the table, the plans/proposals regarding social capitalwhich are made mentioned its maintenance and renewal
are introduced. And as a new movement, "Road
Maintenance Engineering Subcommittee" was set up
under the Road Sectional Committee, the Social Capital
Improvement Council on January, 2013 to examine thetechnological standards concerning road maintenance,
general inspections of the operations, and ideal ways ofstandards for appropriate maintenance of the roadstructures. Maintenance necessity and importance ofaging social capitals are pointed out beforehand, and theMinistry of Land, Infrastructure, Transport and Tourism(MLIT) and related organizations, have worked on
maintenance and inspection including research anddevelopment for them. However, reflecting various recent
movements, not only for institutions under MLIT but also
for local government are requested to take measures, and
it is starting.
2. Aging road structures and current maintenancestatusRoad bridges (bridges with length of 2m or more), anda number of tunnels according to the administrators andconstruction years are shown in the figure. There areabout 700,000 road bridges in its entirety, and the averageage is 35 years (construction year is unclear on 300,000bridges), about 20percent (140,000 bridges) areadministrated by prefectures, and about 70 percent,
480,000 bridges, by cities, towns and villages. Amongthese, 1686 bridges are restricted for traffic, and 326
bridges are closed (as of April, 2012). 5) There are about
10,000 tunnels in its entirety, and the average age is 33years, and there is no big difference in aging with

Table

Recent main plans and proposals regarding
maintenance renewal, etc.
Social capital improvement emphasis plan (August, 2012) 1)
Emphasis target 4 Conduct exact maintenance and renewalof social capitalSocial capital maintenance strategy subcommittee emergency
proposal (January, 2013)2）
Comprehensive enhancement of infrastructure policy for real
maintenance era - kick off "Maintenance policy first year" Ministry of Land, Infrastructure, Transport and Tourism technology
basic plans (December, 2012)3)Emphasis project Ⅱ Social capital maintenance and renewal
project
Emergency economic package for Japanese economic
recovery (cabinet decision in January, 2013) 4)
To conduct the social infrastructure overhaul promptly, and takemeasures for necessary urgent repairs etc.
-(omission) To promote the scheming and strategic
maintenance/renewal of social capital preparing for the aging
in the future(a) Bridge(b) Tunnel
Fig. Number of road facilities by admin and construction year５）

bridges though there is a difference in that prefectures
administrate about 50 percent. About 40 percent of thecities, towns and villages conducted the inspection oftunnels and 30 percent or less of them conducted it of theaccessories to roads before the Sasago tunnel accident,and about 80 percent of cities, towns and villages did not
use the specific procedures for tunnels and accessories. 6)
3. Inspection ProceduresSome administrators did not inspect and somestructures were not inspected, and so the Road
Department of NILIM examined the general inspection
procedures to be conducted in the whole country. Then
we targeted bridges, tunnels, pavement, road accessories,
side slopes, embankments, retaining walls, with the view
point to prevent third party damage caused from structure
corrosion and deterioration etc., discussing with Road
Bureau of MLIT, related organizations and thespecialists.
As for the periodic inspection, some administrators did
not define procedures for structures, and are requested todefine. We will summarize them cooperating with relatedorganizations.
4. Towards forming strategic cycle of maintenance andrepair
Effective and efficient maintenance is requested
because the number of aging structures is increasing. For
that, periodic inspection and diagnosis, formulate
systematic preventive maintenance plan, maintenancecycle establishment, cycle effect to heighten preventive
maintenance, and technical methods of each process arenecessary to rationalize and upgrade, and we will workon emphatically cooperating with related organizations.
① Diagnostic technique of deterioration and damage,and Performance evaluation techniques of structures
We work on the research for, technology for
appropriate evaluation and diagnosis of deterioration anddamage of structures, influence of them on structure
performance, performance evaluation technique ofcurrent load bearing capacity considering the influence ofrepair and reinforcement.
② Structure management method from the viewpointof road network function
The health of road structures should be evaluated as aroute when seen from road user's standpoint. And, whenthinking of the large-scale earthquake etc. health should
be considered based on multiple securities. Therefore, wework on the research technique to clarify the level thatshould be maintained as structure performance, and toevaluate the structure health by one idea from thefunction requesting each link in road networks of acertain area.
③ Techniques to make the entire road structure
long-lived
The entire country must improve to make the entire
social capital long-lived in addition to the view point of
individual structures and maintenance of them forming
road network. For this, it is important to grasp thedeterioration tendency from macro viewpoint and toestablish proper countermeasures. Therefore, we will
construct the database to collect and accumulate theinspection and diagnostic results of road structures andmaintenance information of the repair results etc. on anationwide scale, cooperating with the administrations.
Furthermore we will try to construct maintenancemethods like analysis methods of current state ofproblems, technical corresponding methods to them.
④ Administrator's support
For the maintenance of the structures, not only
technological standards and manuals but also engineers
who can diagnose the structure are necessary.
We try to share and to spread the technical findings
and knowhow owned by NILIM, and contribute to theeducation of engineers on the maintenance site, bypromoting the research and investigation such ascorrespondence to the technical problems andestablishment of technical methods cooperating with theengineers of regional bureaus etc. And, technology
consults on the road structures corresponded by the Road
Department (including the training lecturers andcommittee members), were 134 (end of February, 2013),
and there are technical problems in many organizations,
therefore we will make an continuous effort for directtechnical support to the administrators.
5. Conclusion
The Road Department of NILIM is working on theroad structures, and on study about the road traffic, safety,environment, and landscape.
In the future also, based on the economic situation ofdomestic and foreign society, we will work on the study
cooperating with administration, university, independentadministrative organizations, academic society andassociation,
private sectors, citizens and foreignorganizations.
【Reference】
1)http://www.mlit.go.jp/common/000221986.pdf2)http://www.mlit.go.jp/common/000986603.pdf3)http://www.mlit.go.jp/common/000232351.pdf
4)http://www5.cao.go.jp/keizai1/keizaitaisaku/.../0111_01taisaku.pdf
5)Road maintenance subcommittee 1st subcommittee data
6)Road maintenance subcommittee 2nd subcommittee data