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 the deflection of roads while travelling at normal traffic speed - up to 80 km/h.

TSD data provides continuous pavement deflection profiles, from which bearing capacity indicies can be derived and pavement fatique / residual life can be estimated. The hign accuracy and resolution makes TSD perfect to pin point location with bearing capacity deviations.

ProfilographLaserProfTraffic Speed DeflectometerRight-of-Way ImagingSurface Imaging

Traffic Speed Deflectometer - Measuring Principle

The Traffic Speed Deflectometer measures the velocity of deflection rather than displacement. The measuring of the pavement response is based on advanced Doppler laser technique. Each mounted Doppler laser measures the vertical movement of the road surface. This happens approximately 1000 times per second for each sensor.

Besides Doppler lasers the TSD is equipped with an inertial unit (consisting of gyros and accelerometers), an odometer/encoder, load accelerometer, temperature gauges and a GPS system. The data makes it possible to report deflection characteristics continuously. The collected data are treated in the post processing software program, TSD for windows.

The operator can add events to the data using a keyboard. A photocell is also available for accurate referencing.

An illustration of the TSD, which shows that it is a standard container on a special trailer pulled by a standard truck. The measurement equipment and the data acquisition electronics are located in the container. A controlling computer is located in the driver's cabin.
 

The Container

The measurement equipment and the data acquisition electronics are located in the container on top of the trailer. A controlling computer is located in the driver’s cabin. The data acquisition software saves data from the various measurement systems in a single file during measuring runs. The file is in binary format and contains raw, time related data. The collected data are subsequently treated in the post processing software to obtain bearing capacity results, see results.
The wheel-hubs are constructed in a special way allowing measurments to be made as close as 100 mm in front of the load.
To obtain optimal measuring conditions at all times servo systems and inertial units continuously monitor and control the position of the Doppler sensors.
To measures the pavement response to an applied load of ex. a 10 tons axle a special designed load is mounted below the trailer. The load can be removed.
The driving distance and the driving speed are determined with an odometer, which is mounted below the container.

The Doppler Lasers

The Doppler lasers are mounted on a rigid beam in the container on top of the trailer. One sensor (the one farthest from the load) is used as a reference sensor. This sensor is used in the post processing to compensate for different disturbances while driving. The TSD is designed to be able to contain up to 8 Doppler lasers. A minimum of 4 Doppler lasers is recommend. The more lasers the more accurate revision of the results.
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Traffic Speed Deflectometer
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Traffic Speed Deflectometer
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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.