٨A Case of Utilizing Results

Inspecting road accessories (roadsigns, lighting facilities, etc.)
TAMAKOSHI Takashi, HeadHOSHINO Makoto, Senior ResearcherBridge and Structures Division, Road Department(Key words) Inspection, road sign, lighting facilities, corrosion, crack 
1. Introduction
Road signs, lighting facilities, and othercolumn-shaped accessories installed on roadsides havebeen damaged in various ways including broken
columns, fallen bolts or lamps, and so on. These may
harm third parties such as passing pedestrians orvehicles, so it is vital that these problems are reliably
found by inspections. Many defects are generated atplaces where they are difficult to see such as corrosion
at invisible locations, underground for example (Photo1), or loose bolts high on the structure or cracked
welds, etc. In addition there are a huge number ofthese column-shaped accessories, so it is now
necessary to introduce a rational easy inspection
method which prevents overlooking of defects. The
Bridge and Structures Division has, with thecooperation of the regional development bureaus,
conducted research on the actual state of maintenanceof these accessories and analyzed the results, topropose a draft of a periodical inspection manual forcolumn-shaped accessories equipment.

Photo 1. Column Base
Corrosion Covered byPaving

Photo 2.
Match-mark
2. Outline of accessory inspection
The research results clearly show that amongaccessories with relatively simple structures, a severe
accident such as collapse of the structure or a bolt
falling to the ground or similar accident which
threatens harm to third parties, can be limited to welds,
joints, or specified members, and that corrosion orcracks of such specified parts can develop extremely
rapidly in some installation conditions. On the other
hand, a characteristic of column-shaped accessories isthat it is possible to set patterns of typical structuraldetails and forms of joints since many of them havethe same or similar structures. Based on the above,aninspection manual has been proposed. This manual
provides for general visual inspection and checking
and recording of abnormalities at all specified

locations which are known in advance as relatively
weak points in every structure. In order to accuratelydetect whether or not there are corrosion or cracks
which can deteriorate extremely rapidly, and to find any
loose bolts or other problems, it is usually essential toclosely inspect welds, bolts, etc. using a mobile lift orsimilar device. To reduce the labor requirements ofinspections, bolted joints can also be inspected visuallyfrom a distance by placing match-marks, which aremarks made on each bolt (Photo 2), so that any
abnormality of the joint can be accurately identified. Byclarifying the level of certainty which should beachieved by inspections in the inspection manual in thisway, inspections by a method appropriate to conditions
can be ensured. In addition, by taking care to minimize
weak points in advance when setting or replacing
structures, reliable and economical inspections, and the
reduction of future maintenance cost can be counted on.
Methods of inspecting for corrosion of column
foundations include non-destructive residual thickness
inspections using the ultrasonic pulse reflection
method and a safety evaluation method based on its
results. To look for corrosion of invisible parts underthe road surface, based on research on the actual stateof maintenance, priority inspections in cases of suchcorrosion which can be visually confirmed near theboundary of the road surface and parts buried inasphalt pavement for more than 20 years since
installation have been suggested.
3. Conclusions
The results of this research were reported to eachregional development bureau by the National Highway
and Risk Management Division of the MLIT as
Inspection Manual for Accessories (Road Signs,
Lighting Facilities, etc.) (Draft)” in December 2010.
In the future, studies of the rationalization ofmaintenance, including analysis of inspection data
which is collected will be conducted.