The multi-speed deflectometer: New technology developed for traffic-speed non-destructive structural testing of pavements

The Traffic Speed Deflectometer has transformed pavement structural data collection on highways, where network testing was formerly carried out with Falling Weight Deflectometer, Deflectograph or Beam. However, the Multi-Speed Deflectometer (MSD) is now also available, which can test highways but more significantly, fills a gap for an efficient device for structural testing of urban roads. In these locations, issues that are often overlooked include the frequent slowing or stopping at intersections, cornering, access, the extreme variability of structural stiffness due to pavement subservices and the collection of quality structural data over a wide range of speeds while still ensuring the unimpeded flow of traffic at all times. The Multi-Speed Deflectometer is an economical non-destructive traffic speed pavement testing device used to benchmark the structural capacity of large networks of roads. Data are collected at 1m intervals, usually in both wheelpaths and averaged to 10 or 20m intervals in each lane. MSD structural data have been collected over the last 4 years in multiple regions throughout New Zealand and Italy. When paired with traditional surface profiling from the high-speed data (HSD), reliable traffic records and maintenance history, a comprehensive understanding of the mechanisms of pavement performance can be achieved including both the surfacing and the structural layers. Examples are provided to demonstrate application. Pavements with a poor surface condition can be cross checked against the structural condition to verify whether there is an underlying structural issue. If so, these sites can then be flagged for project level testing and renewal. Sites with poor surfacing condition and no structural issues can be flagged for maintenance or re-surfacing treatment. The right solution for the right problem at the right time and over the right extents can now be economically identified, providing authorities with the capability of assessing the optimum Net Present Value expenditure for any large roading network.