Efforts in the 3-Year Plan for Improving Safety
Development and introduction of new inspection technology
NEXCO CENTRAL is developing new inspection technologies in cooperation with various companies and universities in order to provide safe and comfortable Expressway space with top priority on safety. We are promoting the introduction of a “road surface measurement vehicle” that can measure rutting and cracks on pavements at a high speed while traveling at 100 km / h, and the development of a “high-speed movement inspection system” that can detect deterioration in tunnel equipment at an early stage. , Improving the reliability and efficiency of Expressway maintenance.
Specific Initiatives for Development of New Inspection Technology 1
Developed to quickly and accurately grasp road surface irregularities
Road surface measurement vehicle "Road Tiger"
What is road surface property?
Road surface properties are deterioration or damage to the road surface caused by the running load of the vehicle over time. If left untreated, the handle may be removed, which may lead to an accident. In particular, rutting, cracking, and poor flatness, which are said to be three major properties, require high frequency inspection and repair.
■ Inspection work while traveling at 100 km / h
Until about 30 years ago, the inspection of the road surface of Expressway was performed manually, such as measuring the unevenness of the road surface with a surveying instrument or sketching the road surface condition by hand. During inspections, traffic was congested due to restrictions on the lanes of Expressway, which caused inconvenience to customers. In addition, there was also a problem that working on the road was dangerous.
Therefore, the road surface property measurement vehicle was developed in 1984 by the current Central Japan Highway Engineering Tokyo. You can check while traveling at 100 km / h, eliminating the need for lane regulation. In addition, inspections that previously could only be performed a few kilometers a day due to human power can now be performed 300 to 400 km a day, so labor is greatly reduced and without inconvenience to customers , Making your work more secure and efficient.
● Rutting measurement
Road surface where rutting occurred
Rutting is the process of driving a large vehicle, causing a dent on the road or raising the right and left sides of the road in reverse. When rutting occurs, puddles are formed and handles are removed, so repair is necessary.
Road surface where rutting occurred
The road tiger measures the rutting by irradiating a laser from the front of the vehicle and shooting with a line sensing camera. For example, if you are recessed from a normal road surface, there will be a back and forth shift at the position where the laser hits. By detecting this, the depth of rutting can be measured.
Diagonal laser irradiation causes roadway depression
When measuring the rutting road surface as shown in the above figure, the irradiated laser will shift back and forth, as shown in the figure below
Road surface with cracks
Road surface after repair by seal method
Cracks may occur on roads due to deterioration of asphalt due to vehicle load or long-term use. If cracks are formed, water will penetrate from the road surface and the road will deteriorate, so it is necessary to repair it while the number of cracks is small.
The Road Tiger measures cracks by photographing the road surface with an electronic streak camera attached to the rear of the vehicle while illuminating the road surface uniformly with halogen lights. It is a mechanism to determine cracks from the shadow of the road surface that was taken. It is accurate enough to detect cracks as small as 1mm while traveling at 100km / h.
Road surface cracks taken by Road Tiger
* The cracked part is colored for easy viewing.
Road surface with poor flatness
Due to changes in vehicle load and aging, settlement and steps may occur on the road surface, and flatness may be impaired. Flatness greatly affects ride comfort and may cause vehicle running to be unstable, so repairs are performed as necessary.
The laser displacement meter attached to the left side of the vehicle measures the settlement and steps of the road surface, but errors occur because the vehicle shakes when traveling. Therefore, by detecting the shaking with an accelerometer and correcting the error, the flatness of the road surface is correctly measured. Based on these measured data, repairs are made before the road surface becomes flat.
Laser displacement and accelerometer mounted on the left side of the vehicle
■ Smooth repair plans and more comfortable driving for customers
The Road Tiger, which was introduced in 2003, has further advanced measurement technology. Equipped with GPS (Global Positioning Network) and IMU (Inertial Measurement Device), it can instantly grasp the position and inclination of the vehicle even in places where GPS signals do not reach, such as in tunnels, You can now measure complex swells on roads. By converting this into a 3D drawing, road surface properties can be accurately grasped, making it easier to prioritize repairs and helping to speed up repair planning.
Create 3D drawings that can check the condition of the road surface from various angles based on the measurement data
History of Road Tiger, a road surface property measurement vehicle
- ■ Car 1 (1984-1996)
The speed at the time of inspection is 50-60km. Initially, we used mini-halogen bulbs instead of lasers for rutting measurements. 
- ■ Car 2 (1989-2002)
The speed at the time of inspection is 50-60km. Lasers are now used for rutting measurements. 
- ■ Car 3 (1993-2007)
The speed at the time of inspection is 100km. Speed has improved remarkably. 
- ■ Car 4 (2003-)
GPS (Global Positioning Network) and IMU (Inertial Measurement Device) are installed. "Road Tiger" was named after this 4th car. 
- ■ Car 5 (2010-)
The change from a film camera to an electronic streak camera has increased the measurable distance for each measurement to 2.5 times that of the previous model, enabling more efficient measurement. 
- ■ Car 6 (under development)
Halogen light for irradiating cracks is used for LED. In addition, the power generator installed inside the vehicle is downsized, and the vehicle is also lighter. Reborn as an eco-friendly road tiger. 
Road Tigers continue to run day and night to ensure road safety.
Central Nippon Highway Engineering Tokyo Company Limited
Civil Engineering Department Paving Technology Division
Manager Tatsuya Koizumi
Responsible for overall management of inspection work using road surface property measurement vehicles. A chief engineer with 11 years of road surface measurement history.
Pre-ride inspection work
The Road Tiger simultaneously and precisely measures the three major properties of the road surface: rutting, cracking, and flatness while traveling at 100 km / h. The accuracy of this measurement technology has been confirmed and guaranteed by a performance verification test conducted annually by the Civil Engineering Research Center. This test is performed on the test track of Ministry of Land, Infrastructure, Transport and Tourism National Institute for Land and Infrastructure Management, and the measurement performance of three major road surface properties and the distance measurement performance are confirmed. In addition, every year, regular inspections by measuring equipment manufacturers inspect all measuring equipment. In-house inspections are conducted once every one to two months depending on the frequency of operation, and the performance of three major road surface property measurements is checked. Of course, every time before boarding, you should check the operation before starting work.
Kilopost mark
The measurement is performed by a work leader, a worker, and a driver. Work leaders need to be able to manage the measurement schedule, be mindful of weather changes, the effects of traffic regulations and accidents, and have the ability to judge the plan accordingly. While driving, enter the position data of the kilopost mark (sign indicating the location on Expressway) every 1 km in the passenger seat. All records of Expressway are based on this kilopost mark, so this record is also needed when making repair plans based on the inspection results.
Worker measuring in back seat
Workers are in the rear seats and constantly monitor the condition of the measuring equipment on the monitor. At first glance, it looks like a bus, but it is actually a modified medium-sized truck, so it is not designed to be comfortable. As a result, the rear seats are particularly shaky, and some workers may experience motion sickness until they get used to it. As a custom-built vehicle, the staff is working to improve their skills so that they can respond to unexpected problems such as incorrect operation of measurement equipment.
Warning sign at the rear of the vehicle
During measurement, we always consider the safety of customers who use the Expressway. At the rear of the vehicle, an indicator is illuminated to notify the following vehicle that the vehicle is undergoing inspections, and we try to keep the driving speed and lanes constant. The distance between vehicles is kept at least 100m away from the vehicle in front of the vehicle in order to avoid an emergency, and the vehicle is not run alongside the vehicle next to the vehicle so that the following vehicle can pass.
Based on the data measured by Road Tiger, we have a repair plan. To ensure that customers can drive safely, safely and comfortably, we prioritize construction sites so that repairs can be made before road damage exceeds standard values, and we are proceeding smoothly with repair plans. Thirty years after the development of the road surface quality measurement vehicle, our job is to work behind the scenes with little direct contact with customers. However, we are proud to play an important role in supporting the safety of Expressway, and will continue to provide Expressway that are easy for customers to drive.
Specific Initiatives for New Inspection Technology Development 2
Detects anomalies in the tunnel while traveling.
High-speed moving inspection system
The University of Tokyo and NEXCO CENTRAL are jointly developing a "high-speed mobile inspection system". This is an inspection technology that utilizes `` high-speed image processing technology '' researched and developed by Professor Masatoshi Ishikawa of the Graduate School of Information Science and Technology of the University of Tokyo, and it is possible to shoot objects such as cracks in the tunnel ceiling while driving at 100 km / h. It is possible to capture an image that keeps the image at the center of the frame and minimizes blurring. From the images taken, you can check if there is any abnormality in the fixing hardware of the jet fan at the top of the tunnel. The installed camera aims to monitor the displacement of equipment with a width of 10 mm or more and the progress of cracks with a width of 0.2 mm or more. We are also developing a system that automatically detects positional shifts of fixtures and the like and the progress of cracks in concrete compared to images taken in the past.
Shooting inside the tunnel (image)
Image of mounting on vehicle
While driving at high speed at 100 km / h
Picture taken
(Fittings for jet fan)
Developer Interview
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To improve safety,
What kind of technology development we are doing
The technical development staff speaks.
List of activities
