Keywords: rutting, roughness, pavement management system, flexible pavements, close range photogrammetry.

The cost of data collection is often the largest single component for any pavement management system (PMS). Rutting is one of the important items collected for PMS. It develops under the wheel paths as a result of permanent deformation in any of the pavement layers or the subgrade. It is generally caused by the consolidation or lateral movement of the materials due to the cumulative axle loads over the life of the pavement. Rutting is a safety consideration related to the potential of hydroplaning as well as a maintenance problem [1,2].

Over the past decades, new automated techniques which utilize laser, sonar, or ultrasonic technologies were developed in Europe and America to measure rut depth [3,4,5]. The automated rut depth measurement techniques have a number of valuable benefits such as convenience; require fewer personnel; safety of the personnel in charged of collecting the data and the travelling public; and also monetary and time savings. Unfortunately, the cost of such techniques is beyond the funds allocated for such a purpose by most of the transportation agencies in the developing countries. Therefore, they use the traditional methods which are slow, disrupt the flow of traffic, and risk the safety of the personnel involved, to measure rut depth.

This paper investigates the potential accuracy and limitations of using a reasonably priced technique which uses locally available tools to measure rut depth in the developing countries. The proposed technique utilizes close range photogrammetry. Such a technique has the potential to substitute the traditional technique which is presently used by transportation agencies with limited resources. To carry out this investigation, four highway sites were selected and videotaped by stereo-pair cameras mounted on the back of a vehicle moving at a speed of 20 km/hr. The rut depth for each section was determined by using the photogrammetric, the straight edge, and the levelling techniques.

The absolute mean of the difference between the point elevations obtained by using the photogrammetric and the levelling methods were 0.308, 0.280, 0.348, and 0.365, for sites 1 to 4, respectively. The similar difference between the point elevations obtained by using the photogrammetric and the traditional methods were 0.418, 0.441, 0.501, and 0.452 for sites 1 to 4, respectively. It can be concluded that the close range photogrammetric method has the potential to produce acceptable results compared to that obtained by using the traditional method.

1

Banks J.H., "Introduction to Transportation Engineering", Second International Edition, McGraw-Hill, New York, 2004.

2

Huang Y.H., "Pavement Analysis and Design", Prentice Hall, Englewood Cliffs, New Jersey, 1993.

3

Kandhal P.P., Cooley L.A. Jr., "Accelerated Laboratory Rutting Tests: Evaluation of the Asphalt Pavement Analyzer", NCHRP Report 508, TRB, National Academy Press, Washington D.C., 2003.

4

McGhee K., "Automated Pavement Distress Collection Techniques", Synthesis 334, Transportation Research Board, Washington D.C., 2003.

5

Bennett C.R., Wang H., "Harmonic Automated Rut Depth Measurements", Transfund New Zealand Research Report, 2002.

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