Design Solutions

Gloucestershire County Council (GCC) has started surveying proposed highway maintenance schemes with Deflectograph to help develop and refine design proposals.

Since the National Indicators switched from Deflectograph to SCANNER in 2006 many local authorities stopped undertaking routine Deflectograph surveys.

SCANNER is an excellent survey technique to identify pavement deterioration, but it does not always provide information on the cause or extent of deterioration.

Faced with the need for disruptive road closures for maintenance work, Gloucestershire County Council (GCC) recognised that getting the design and specification correct can minimise the need to later return visits to address premature failures. The Council subsequently commissioned surveys for seven jobs in November 2017.

When planning maintenance schemes, the use of Deflectograph data can assist in understanding the extent and severity of deterioration, and allow optimum solutions to be identified, that balance cost against the desire to achieve a specified design life.

W.D.M. Limited offered support in interpreting associated coring and traffic data, processing the survey results and training. This provided detailed outputs showing overlay requirements to achieve a two-year life for the schemes, allowing GCC to develop and finalise their scheme designs.

The benefits to GCC were that in ensuring the most appropriate treatments are designed, their contractors know and understand the scope of work at time of starting, minimising over-runs if unforeseen conditions occur.The typical cost of Deflectograph survey for 1km of carriageway is less than 1% of typical surfacing costs for the same scheme.

Gloucestershire County Council (GCC) are so satisfied with the results from the first set of surveys that they are planning more than 30 additional sites for survey in Spring 2018.

Highway Authorities have used Deflectograph Surveys for more than 30 years to indicate the strength of their asphalt roads.

The structural condition of pavements is assessed by measuring the transient deflection of the road surface under the action of a rolling wheel at standard loading conditions.

The maximum deflection of the road surface is measured at about 4m intervals, simultaneously in each wheel path, while the Deflectograph travels at a constant speed of 2.5 km/h. The close spacing of the measurements enables short lengths of weakness to be identified.

W.D.M. Limited manufacture the British version of the Deflectograph, which is a fully self-contained vehicle-mounted system of standard configuration, consisting of a deflection measuring assembly and data recording electronics. Standard rear axle loading (6 – 10 tonne) is achieved using ballast fitted to the vehicle chassis.

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