Improving the precision of Light Weight Deflectometers through annual correlation trials

The Light Weight Deflectometer (LWD) is a portable and cost effective device that plays a vital role in checking the quality of highway foundations and base installations for sports facilities, such as football pitches and athletic tracks. As the device is accepted for use as part of compliance testing it is essential that the results produced are reliable. This paper summarises the results of two UK-wide correlation trials carried out in 2021 and 2022. Machines and operators from 42 organisations attended the trials, where the performance of 175 LWD devices was assessed against the larger Falling Weight Deflectometer (FWD). This paper provides some background to the use of LWDs and the design of the trial, including the collection and analysis of data. The relationship between the LWD and the FWD, including data variability and the influence of different testing regimes was examined. The main findings of the trials are summarised and recommendations are made to maintain the precision of LWD devices.