Germany’s Federal Highway Research Institute (BASt) is using a specialized semi-truck to analyze and map road surfaces. The research vehicle uses GNSS, scanner and camera equipment to record the condition of road surfaces and the substance of the asphalt surface, providing the basis for optimum maintenance planning.

The truck is part of the BASt’s MESAS program, which began in 2018. The unique measuring vehicle is a multi-functional assessment tool for fast-moving substance detection, such as for structural evaluation and design of pavements.

For the MESAS program, innovative measurement technology was installed on a single-axle semi-trailer, with all measurement systems synchronized and georeferenced using a GNSS system.

The MESAS measuring vehicle is 14.5 meters long and weighs 22 tons. At speeds of up to 80 km/h, MESAS records road condition parameters with high precision. (Photo: BASt)

The vehicle includes:

• the Pavement Profile Scanner PPS-Plus from Fraunhofer IPM
• a laser-based Traffic Speed Deflectometer (TSD) that measures short-term reversible deformations of the road surface
• a georadar that detects layer thicknesses and inhomogeneity of the road superstructure
• ambient cameras that provide images for interpreting the georadar measurements

During test runs, the vehicle system successfully measured more than 11,000 kilometers of the country’s trunk-road network. Now it begins regular operation.

“MESAS is a globally innovative measuring system,” said Dirk Jansen, department head, BASt. “Here we have a really powerful tool at our disposal with which we can make an innovative and significant contribution to the further development of conservation planning.”

Laser-based measuring systems record the road surface without contact. The measurement data are synchronized and georeferenced with the help of a GNSS system. Software tailored to the application manages the data and supports route planning and quality assurance during operation. (Diagram: Greenwood Engineering A/S All Rights Reserved (modified).)

Millimeter precision. The Pavement Profile Scanner PPS-Plus records the transverse evenness of the road surface with high precision. The scanner, the size of a shoe box, is mounted on measuring vehicles and scans the road surface with an eye-safe laser beam over a width of about 4 meters. The distance to the road surface is determined with sub-millimeter accuracy using phase-shift technology.

The laser scans the surface with the aid of a rotating polygon mirror perpendicular to the forward movement of the vehicle and generates 800 profiles per second. Each profile consists of up to 900 measuring points, depending on the selected measuring frequency. In this way, the PPS generates a detailed 3D height profile of the road surface.

At traveling speeds of 80 km/h, the measuring point distance in the longitudinal direction is approximately 28 millimeters; in the transverse direction it is 4.5 millimeters. It also provides photorealistic grey-scale images of the road surface that show millimeter-thin structures, such as small repairs and patches.