●Messages from Departments and Centers of NILIM

Formation of Resilient Road Networks andReallocation of Road Space—Technology Policies for Road Infrastructure Based on Constant Monitoring
and a Database—
TSUKADA Yukihiro
Director of the Road Department(Keywords) Road traffic census, probes, database, road assets, maintenance, road space reallocation
1. Internationally Competitive 21st Century Road
NetworksThe Committee on Formation and Operation ofExpressways issued its interim report in December
2011, based on changes in social and economic
conditions, medium- and long-term future prospectsfor Japan and for international society, and theexperience of the Great East Japan Earthquake. Theinterimreportoutlinedthefunctions
ofexpressways—strengthening access to airports andports, ensuring a service level of 60–80 km/hour
between major cities and regions, and ensuring anetwork that will continue to function during
disasters—in line with the basic principles:reorganizing and strengthening the national land in theface of population decline, and increasing people’s
trust in the national land. Noting that “If it’s connected,
it’s a network!”, it sets clear goals for improvements
and management to eliminate missing links usingeasy-to-drive national highways and permanent
two-lane expressways.
2. Completion of monitoring of road networks
In order to plan, improve, and manage such road
networks which cover the national land, a system forconstantly monitoring and managing the state of roadtraffic throughout the country is required. The roadtraffic census, which is an example of such monitoring,surveys the traffic volume and traveling speed on
about 190,000 kilometers of trunk roads throughout
Japan every five years, and its findings are used toplan road improvements. The 2010 census actively
introduced automated surveys using constant traffic
volume observation devices and portable traffic
counters, made possible by ITS-based traffic
measurements. Traveling data obtained by probe carsystems operated by the private sector have also been
widely used. Full-scale 24 hour/365 day road trafficmonitoring has begun. Systems to monitor road traffic
throughout Japan have only partly been established,
but a large quantity of data which will be useful forenacting policies has already been obtained. As shownin Figure 1, as a result of population decline, the risein the number of vehicles and vehicle kilometers
traveled have both peaked, and are beginning to fall
(average traffic volume down 2.6% from five yearsago). In view of this reversal, we should clarify

economicconditions,theeffectivenessofcountermeasures, impact of disasters, etc. using acontinuous and high-density observation system. The
results of traffic monitoring of high-standard road
networks throughout Japan, which were continuallyobserved from immediately after the Great East Japan
Earthquake, were effectively used to set alternativeroutes and to enact emergency countermeasures forcarrying people and materials to the disaster region. A
trial by automakers, etc. to jointly collectprivate-sector probe data to publish viable routes on
the web in real time was evaluated as extremely
effective, and so efforts to integrate this with publicprobe data obtained by ITS Spots are expected. Figure
2 shows the state of congestion of the road network in
the Tokyo region after the earthquake, obtained byanalyzing probe data. It accurately reproduced andevaluated the state of congestion for the entire networkand for each section, and will help clarify thecondition of road networks spanning adjacentmanagement regions when a disaster strikes, and canbe used to prepare countermeasures.
(Million vehicle-kilometers
traveled/24 h)(1 million people, 1 million units)
Vehicle-kilometers traveled
Total population
Automobile fleet

’80

’82

’84

’86 ’88

’90

’92

’94

’96

’98

’00

’02

’04 ’06’08‘10Figure 1. Changing population, automobile fleet,vehicle-kilometers traveled●Messages from Departments and Centers of NILIM

LegendNo data

Analysis of average traveling speed based on probe data
Declined sharply from 21.3 km/hr before the earthquake to 6.2
km/hr afterpedestrians, cyclists, and other road users”2). Specificmeasures now required include reallocating andeffectively using limited road space, and placing
priority on pedestrian and bicycle traffic alongcommunity roads.
Under such circumstances, while the number oftraffic accidents is falling, bicycle related accidents
have increased in the past 10 years, so it is necessary
to prepare bicycle network plans and establish
comprehensive rules for the design and use of safe andconvenient bicycle spaces. The Ministry of Land,
Infrastructure, Transport and Tourism and National
Police Agency plan to draw up a guideline for thesepolicies, which the NILIM is supporting by organizing
network planning studies and gathering detailed
technological knowledge on the structure of normal
road sections and intersections.
Sidewalk

Vehicle lanes
Street sidetrees

Four lanes

Figure 2. Reproduction of state of congestion in theTokyo region after the Great East Japan Earthquake
3. Conservation of a resilient national land
infrastructure and road assets
The interim report on the review of the Priority
Project for Public Asset Improvement (November2011) includes discussions of strategic maintenanceand refurbishment management to deal with thedeterioration of public assets under limited budget,and the development of technologies which willcontinue to function and withstand damage during
disasters.
The NILIM is actively analyzing and surveying thedamage to road structures following the earthquake,and has used the results to review the standards forroad bridges, road earthworks, and other roadstructures. In addition to clarifying the mechanisms ofdamage to road structures by tsunami, the NILIM isalso considering the need for design standardsspecifically considering the impacts of tsunami, and isdefining earthquake resistance performance required
for earthwork structures, which are part of the roadnetwork, to ensure that the roads can still be used after
an earthquake, and intends to reflect the findings intechnological standards. As the quantity of aged roadassets increases, many cases of serious damage andaccidents to bridges have been reported both insideand outside of Japan. Considering the declining
population, falling birth rate, aging of society, andharsh financial conditions, the NILIM is now
researching ways to maintain the functions of existingroad structure assets as economically as possible, andcreating new road structures with superior durability
and reliability to minimize the burden of maintenance.
4. Reallocation of road space (creatingenvironments for cyclists)
In Japan, as the trunk road network has been
established, there have been discussions on changing
the objective of road policy from “dealing with thegrowth in automobile traffic” to “coexistence ofVehicle lanes

Sidewalk

Guard rail

Street sidetrees

Bicycle pathThree lanes

Bicycles travel on thebicycle path

Guard rail

SidewalkVehicle lanes

Figure 3. Model of bicycle traveling environment(Nagoya)3)
References
1) Ministry of Land, Infrastructure, Transport and Tourism, RoadBureau: Interim Report of the Committee on Formation andOperation of Expressways, December 23, 2011.
2) Ministry of Land, Infrastructure, Transport and Tourism, Road
Bureau: Interim report of the Council of Social Infrastructure,
Road Committee, Basic Policy Subcommittee (Draft), February
7, 2012.
3) Document from the Chubu Regional Development Bureau ofthe Ministry of Land, Infrastructure, Transport and Tourism.