Traffic Speed Deflectometer

Traffic Speed Deflectometer (TSD) is a rolling wheel Deflectometer for network level bearing capacity measurement. TSD uses patented Doppler technology to measure pavement deflection while travelling at normal traffic speed - up to 80 km/h (50 mph)

TSD data provides continuous pavement deflection profiles, from which bearing capacity indices can be derived and pavement fatigue / residual life can be estimated. The high accuracy and resolution makes TSD perfect to pin point locations with bearing capacity deviations. This information allows you to plan exactly from where to where to repair.

TSD can be combined with subsystems collecting functional data simultaneously and synchronized with structural data.

Traffic Speed DeflectometerProfilerLaserProfLaserProf BikeLaneTrailerRight-of-Way ImagingSurface Imaging System


Dedicated software has been developed for post processing of data produced by the Traffic Speed Deflectometer. Measurements from a Greenwood TSD or a Greenwood multifunctional vehicle can be treated with the same post processing software package and synchronized results can be seen and exported.

Using the post processing software for a TSD measurement file the software shows result in 2D and/or 3D. When exporting results the software produces a files in text or excel format that, among other information, contains:

• Chainage
• Temperature (air and road)
• Deflection slopes
• Structural Curvature Index 300, SCI 300
• Maximum Deflection under the load

The result file is based on a binary file created by the data recording software during measuring. Different settings such as the number of columns and the output frequency can be changed by the user. The user can select to operate in imperial units or metric units.

Below some of the different results are discussed:

Deflection Slope

The Doppler sensors measure the velocity of the deflection. The Deflection slope is the slope of the deflection, where the Doppler measure.

Maximum Deflection and Structural Curvature Index 300

Based on the Deflection slopes we can calculate bearing capacity characteristics. The maximum deflection, d(0), is the deflection under the center of the load. The Structural Curvature Index 300, SCI300, is d(0) minus the absolute deflection 300mm in front of the center of the load, d(300), that is SCI300 = d(0)-d(300).

Examples from network measurements

The graph below shows an example of the Structural Curvature Index 300 as a function of chainage (33 km) of the same Danish road section measured in 2005 (blue), 2006 (green) and 2007 (red). The road section between km 6 and km 7.5 was repaired between the measurements in 2005 and 2006.

New wearing course was added around km 20 between 2005 and 2006. The graphs for 2006 and 2007 are almost identical, and no road change has been made between these two measurements.

Examples of results

The figure below shows SCI300 data from app. 100 m of the same section of road measured at 4 different driving speeds.

Product pages
Traffic Speed Deflectometer
PDF: 1.4 mb
Traffic Speed Deflectometer
Display Examples
PDF: 3.9 mb
Traffic Speed Deflectometer
MnRoad Project
PDF: 2.1 mb
Traffic Speed Deflectometer
PDF: 2.1 mb
Traffic Speed Deflectometer
FWD User's Group 2012
PDF: 8.8 mb
Traffic Speed Deflectometer
ARRB 2010
PDF: 508.4 kb
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The Traffic Speed Deflectometer is patented under the following patent numbers: 819196 in Europe, 694347 in Australia, 6119353 in USA and 3850875/3851342 in Japan.