CTS’s Falling Weight Deflectometer (FWD) gains accreditation for another year

Having recently attended the annual DPT accreditation trials operated by TRL, CTS’s Falling Weight Deflectometer has successfully passed, one of just 19 FWD machines in the UK.


Each year the trials are held on the twin straights of MIRA proving ground, to assess the performance of all FWD machines that intend to operate on the National Highways Road network. Only machines that are found to perform satisfactorily may subsequently be used on the strategic road network. The trial is conducted over three days where machines are inspected prior to undertaking a number of test runs to ensure the reproducibility and accuracy of the deflection measurements.

Following successful attendance of the trial, ongoing data is submitted to TRL throughout the following year to ensure machines remain fit for purpose when producing data used in assessment of road pavement performance.

We asked Phil Church, Project Manager for CTS to explain exactly what a Falling Weight Deflectometer is, and what is it used for.

“A Falling Weight Deflectometer (FWD) applies a dynamic load to the surface of the pavement as a simulation of the loading caused by a moving wheel, this load is created by a mass dropped from varying heights onto a plate in contact with the pavement. The response of the pavement is measured by a series of geophones at various prescribed spacings in contact with the pavement surface and the information is recorded electronically for analysis of the deflections induced. Close up of FWD

The data generated by the FWD is used to assess the structural condition of the pavement. The measured deflections caused by the application of the load can be post-analysed to determine an estimate of the elastic modulus, stresses and strains of the analysed layers; also, when used over joints the load transfer efficiency of the joint can be determined.

FWD testing on highways is carried out in accordance with Design Manual for Roads and Bridges, CS229. For use on the highway and in accordance with CS229 all FWD machines are required to attend an annual accreditation and correlation trial, something that I am pleased to say that we have attended and passed again this year and look forward to receiving our updated certificate.”

To enquire about FWD tests, get in touch with a member of the team today.

CTS’s structures and pavements team also offer an extensive range of complementary testing solutions, allowing us to investigate the construction and condition of the country’s roads and pavements.

Construction Testing
01302 352 652