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RAV / Scanner Surveys

Road Assessment Vehicles (RAVs) carry out high speed data acquisition and recording of road surface conditions, including automatic recognition of surface cracking. This gives performance indicators to enable maintenance work to be prioritised and National Indicators to be calculated.

W.D.M. Limited has been undertaking high speed data acquisition surveys since the late 1980s and has been using RAVs, which include the automatic measurement of road cracking, since 2000. Over that period the Company has developed expert knowledge and skills to undertake the surveys quickly, but safely, and to process and deliver the data accurately to agreed timescales.

These vehicles have been the primary provider of SCANNER survey data throughout the United Kingdom. The vehicles are designed to survey at speeds up to 100 km/hr while measuring and recording:

  • roughness in the left-hand wheel path
  • texture in the left-hand wheel path centre of lane and right hand wheel-path
  • individual wheel path rut depths measured under a 2m straight edge with 20 sensors over a 3.2 metre width
  • transverse profile edge defects
  • video record of the view ahead providing images at 5m intervals
  • longitudinal gradient, horizontal radius of curvature, lane crossfall
  • differentially corrected GPS co-ordinates corrected to OSGRs

The addition of automatic road 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 pavement road and highway surface defects measured and recorded define the latest UK National Indicators for principal and classified roads.

When input into a PMS they can be used to define maintenance schemes and place the work in priority order.

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

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

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

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