Road Assessment Vehicle (RAV)

W.D.M. Limited has been using Road Assessment Vehicles (RAVs) to undertaking high speed data acquisition surveys since the late 1980’s. These vehicles have been the primary provider of SCANNER survey data throughout the US and UK.

The RAVs, which have included automatic measurement of cracking since 2000, provide performance indicators to enable maintenance work to be prioritized, while the surface defects measured and recorded define the latest National Indicators for principal and classified roads.  

The RAV is independently accredited annually by TRL and its geometric system is certified to have a minimum operational speed of 0.3mph, which is particularly significant when operating in an urban environment. The vehicles are designed to survey at speeds up to 60mph while measuring and recording:

  • roughness in the left-hand wheel-path
  • texture in the left-hand wheel-path center of lane and right hand wheel-path;
  • individual wheel-path rut depths measured under a 6.5 feet straight edge with 20 sensors over a 10.5 feet width;
  • transverse profile edge defects;
  • video record of the view ahead providing images at 16.4 feet intervals;
  • longitudinal gradient, horizontal radius of curvature, lane crossfall;
  • differentially corrected GPS co-ordinates corrected to OSGR’s.

The addition of automatic crack recognition enables the RAVs to completely replace manual visual surveys with objective and more repeatable measurements, obtained in greater safety from a vehicle travelling at normal road speeds.

The measurements of alignment together with the video record provide an ideal way of defining site categories for use with surveys of skid resistance.

RAV has added two new measures to its output, identified from the SCANNER research. These measure edge deterioration and transverse roughness, which it is expected will provide further indicators of conditions on narrow, particularly lower category roads where conventional ruts do not develop but the road surface becomes deformed.

This process of continuous improvement and enhancement of the WDM® survey fleet is an integral part of the WDM® quality management process.

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