Pavement plays an important role in providing safe, secure, and comfortable expressway spaces. Pavements are road structures that are most familiar to customers who use expressways.
Since pavement deteriorate due to traffic loads and the surrounding environment, it is necessary to accurately grasp the condition at all times and perform appropriate maintenance.
We have developed a “Road Surface Condition Measuring Vehicle” that can grasp the condition of the road surfaces while driving at high speed, and have been conducting road surface surveys on expressways for over 30 years.

Road Surface Condition Measuring Vehicle

Our independently developed high-speed road surface condition measuring vehicle “Road Tiger”
In addition to being able to measure ruts, cracks and flatness (σ3m, IRI) at any speed up to 100km/h, it can also take longitudinal and transverse measurements of the road surface using GPS and gyro technology.
Previously, inspections could only be done manually for a few kilometers per day, but this vehicle allows inspections to be performed over 300 to 400 kilometers per day, enabling smooth and safe measurements without having to follow the lane regulations even when customers are driving on the road.

Measurement of Rutting

The road surface is irradiated with 54 lasers from the laser projector in front of the vehicle, and rutting is measured by photographing it from above with a line sensor camera.
For example, an area of the road that is indented more than the normal road surface will cause a deviation in the position of the laser beam. Using the principle of triangulation, the rutting depth is measured by detecting this deviation.

Rutted road surface

Measurement principle

Crack Measurement

Uniformly illuminating the road surface with halogen light creates shadows on the cracks, which are measured by photographing the road surface with a digital streak camera at the vehicle’s rear.
The Road Tiger does not miss cracks even as small as 1 mm while running at 100 km/h.

Cracked Road Surfaces

Photographed road surface cracks
* Cracks are colored to make them easier to see.

Flatness (σ3m/IRI) Measurement

A laser displacement meter attached to the left side of the vehicle measures road subsidence and unevenness. However, since the vehicle shakes during measurement, the accelerometer detects and compensates for the shake while measuring the flatness of the road surface.
*IRI (International Roughness Index): A flatness evaluation index that has a strong correlation with ride comfort, proposed by the World Bank in 1986

Road surface with reduced flatness

Accelerometers and laser displacement meters

Longitudinal and Transverse Shape Measurement

Using the GPS (Global Positioning System) and the electronic reference points installed by the Geospatial Information Authority of Japan, the longitudinal and cross-sectional shape of the road surface is measured in 3D. The IMU (Inertial Measurement Unit) technology used in aircraft, etc., can instantly determine the position and inclination of the vehicle and measure the complex undulations of the road surface even in places where GPS signals cannot be received, such as in tunnels.

Illustration of vertical and horizontal measurement

Road surface with complex undulations

GPS receiver

3D evaluation of road surface

IMU (Inertial Measurement Unit)

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