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

TSD production versions available (photo)

The Danish Road Directorate owns a production version with 4 Doppler sensors, the yellow on the photo. The other TSD in the photo (the white) is owned by TRL/Highways Agencies in the UK. It is possible to add more than 4 Doppler sensors, that the existing devices operate with.

TSD network measurements in Denmark

The Danish TSD operated by the Danish Road Directorate has measured the Danish state road network - approx. 3300 km - since 2005. The graph below shows an example of the Structural Curvature Index 300 as a function of chainage (33 km) of the same road section measured in 2005 (blue), 2006 (green) and 2007 (red). The road section between km 6 and km 7.5 has been repaired between the measurements in 2005 and 2006.

Also wearing course has been 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.

Bearing Capacity

The bearing capacity of roads or rails can be judged by the deflection pattern from a heavy load. To measure deflections on roads and rails while driving at normal traffic speeds has proven to be a difficult task. Greenwood Engineering has patented a new measuring concept using Doppler laser sensors in an effort to solve the problem. The device for measuring deflection of roads at high speed are developed in co-operation with Delft Technical University (Netherlands) and the Danish Road Institute.

Traffic Speed Deflectometer Concept

The basic idea of the Traffic Speed Deflectometer concept is to measure the velocity of deflection rather than displacement, see measuring principle. As the velocity of deflection is the derivative of displacement it is possible to calculate the displacement subsequently, see results.

Cost-benefit analysis

Because the TSD measures at traffic speed it is possible to measure several hundred kilometers of road per day. This is a high production capacity compared with other stationary or slow moving bearing capacity equipments. Furthermore, the TSD data are continuous and there is no need for road closure when measuring.

Change of name from HSD to TSD

Greenwood Engineering has August 2006 decided to change the name of the High Speed Deflectograph (HSD) to a Traffic Speed Deflectometer (TSD), see the product information to the right.

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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.