Investigation on the combined effect of lateral offset and transverse profile shape on rut depth measurement accuracy

Rutting is one of the dominant pavement distresses, and the accuracy of rut depth measurements can substantially impact on the maintenance and rehabilitation (M&R) strategies and on funding allocation. A 13-point-based laser sensor is commonly used in China for rut depth measurements; nevertheless, errors are inevitable if the vehicle on which the lasers are mounted wanders during the measurement process. Therefore, there is an urgent need to assess the impact of this factor on the accuracy of rut depth measurements. In this paper, three representative rut shapes with high and medium severity levels were obtained from a database of 3,710 field transverse profiles which were collected using a laser bar. Based on the reconstruction of real transverse profiles, the impact of different offset magnitude on the accuracy is evaluated. Results show that there is a combined effect of offset magnitude and profile shape on rutting depth measurement accuracy, and, as expected, the errors increase for larger vehicle wandering. These findings suggest that vehicle wandering should be minimized, especially on the roadways with severe rutting. Therefore, the maximum acceptable offset within which reliable M&R decision can be taken is 300mm. In addition, statistical analysis results show that the upheaval on the right side is a dominant shape factor which affects the rutting depth measurement accuracy. Such a shape characteristic indices, in most of the cases, smaller offset error on the left than on the right, and an overall increase of the overestimation error.