Ground Penetrating Radar and Specialised Road Surveys

Whilst the different applications of Ground Penetrating Radar are numerous, the traffic speed approach is predominantly applied to subsurface investigations on transport networks and structures, such as Roads, Runways, Bridges and Tunnels.

For the above applications, a traffic speed GPR survey can accurately establish the 
construction and condition information up to 2 metres beneath the surface. The survey is non-destructive and non-disruptive, as 
data is collected at traffic speed and requires no traffic management.

More specifically, the following information can be gained from carrying out Traffic Speed Survey's:

• Construction changes in pavement Materials and Layers
• Changes in Material and Layer Types
• Changes in Layer Types
• Moisture Profiles
• De-lamination and De-bonding
• Subsurface Consolidation
• Voiding.

By using a 4K Digital Video System calibrated to the human eye instead of using retroreflectivity meters, actual sign performance can be measured in terms of the true sign interaction with the driver where other factors, such as sign orientation and obstructions, can be taken into consideration.

As always with video systems, they allow a greater degree of quality assurance rather than relying on discrete measures, which in this case are taken from retroreflectivity meters.

The sign images are stored and archived. With more and more traffic on the UK’s roads and Hardshoulder running it is no longer possible to carry out the traditional methods due to safety concerns.

​Not only is Traffic Speed Retroreflectivity cost effective it is inherently safe and produces consistent results to allow comparisons year on year.

Our non-intrusive survey methods minimise disruption while delivering accurate and detailed information about underground structures and road surface conditions.

Using 4K imagery captured at night combined with specifically calibrated lighting we are able to obtain the retroreflectivity of line markings. The value of retroreflectivity determines the visibility of the line markings at night. Our research programme has produced algorithms to convert grey-scale intensity to Retroreflectivity Luminance (mcd.m-2.lx-1) 

​The system operates at traffic speed and the lines are illuminated by a high intensity LED source. The receiving CCDs are calibrated to reproduce comparable grey-scale outputs. The system collects left and right edge line marking retroreflectivity simultaneously from the digital video. Analysis is automated and outputs are a measurement of retroreflectivity averaged over 2 meters in Geo-Referenced form.

Line These results can be statistically analysed along with street lighting information to produce green, amber and red traffic light style output to highlight the areas requiring improvement. Outputs are in CSV, Shapefiles or as per the client’s specific requirements.

Using the same methodology as we use to detect line marking retroreflectivity we are also able to automatically locate road studs and measure their Retroreflectivity Luminance (mcd.m-2.lx-1).

The system operates at traffic speed and the studs are illuminated by a specifically calibrated LED source. The receiving CCD's are then calibrated to reproduce comparable grey-scale outputs. The grey-scale values are converted to retroreflectivity luminance using Impulse Geophysics proprietary algorithms. Along with the automatic detection of the Roadstuds colour we can then determine whether the stud is working and reflecting as intended.