Articles in Taxonomy

FPP – Measurement of the longitudinal evenness of cycle tracks

The Belgian Road Research Centre has a footway profilometer to measure the longitudinal evenness of cycle tracks and other surfaces. A scooter with a trailer travels at a constant speed of 20 km/h on the surface to be surveyed. Using a laser and an accelerometer, the distance between the trailer and the road surface is recorded every 3 cm. The GPS coordinates and the distance travelled are recorded as well. From the measured longitudinal profile is possible to calculate the coefficient of evenness (for wavelengths of 0.5 m and 2.5 m) or other indicators of evenness.

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Falling weight deflectometer (FWD) – Measurement of structural road characteristics

The Belgian Road Research Centre has a falling weight deflectometer to measure the temporary deflection of roads under heavy traffic loads. A falling weight is dropped from a standing vehicle onto a metal disc laid on the road surface. A rubber interface on top of the metal disc damps the impact so as to simulate the passage of a heavily loaded wheel axle of a lorry. Nine sensors in the vicinity of the impact zone record the temporary deflection of the road surface. A deflection bowl can be determined from the measured data. The FWD is suitable for measurements on all types of pavement (from flexible to rigid) and for use on road networks. Usually one measurement is performed every 100 m. A single measurement takes less than two minutes.

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Workshop on the Curviameter: Interpretation and Exploitation of Measurements

On January 28 and 29 2015, the Belgian Road Research Centre hosted a workshop on the Curviameter. The objective of the workshop was to bring together specialists and users of Curviameter measurement data: current and former end-users of Curviameter data, road managers and road engineers, scientists who published articles about the interpretation of Curviameter data, and persons interested in the measurement device and in the data it provides.

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Structural analysis

A road is more than just a trafficked surface; there is a whole structure underneath. A road structure is usually composed of a subgrade soil, a subbase, a base, and a surfacing. Each course has a specific function: frost resistance, drainage, bearing capacity, etc.

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Longitudinal profile analyser (“Analyseur de profil en long”, or APL) – measurement of the longitudinal evenness of roads

The Belgian Road Research Centre has a longitudinal profile analyser for continuous measurements of the road profile. The measured data can be used to quantify the longitudinal evenness of a road and to calculate inticators such as the coefficient of evenness (CP, which stands for coefficient de planéité in French) and the international roughness index (IRI). Longitudinal evenness is an important factor for the safety and comfort of road users. The high accuracy of measurement makes the APL also suitable for research purposes. The measuring wheel bumps up and down with the relief of the road. This movement causes a change in the angle formed by the wheel-bearing arm in its hinge point. An inert pendulum in the bearing arm transforms the road profile into an electric signal. The angle between the bearing arm and the pendulum is recorded every 5 cm. This allows a graphic representation of the “pseudo-profile” of the road surface. A constant survey speed of 21.6 km/h, 54 km/h or 72 km/h is required.

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