12. System for determining the degree of deterioration of wooden sleepers using images of railway tracks in front of trains

On sections of railway lines constructed mainly of wooden sleepers, there is a risk of “derailment by gauge widening” due　to inadequately fastened rails caused by the decay of wooden sleepers.
For this reason, the number of defective wooden sleepers and the state of individual sleepers needs to be continuously controlled, particularly along curving track. However, visual inspections of huge numbers of sleepers requires enormous labor.
To solve this problem, we developed a system that uses video captured with an off-the-shelf video camera to automatically detect and judge the degree of deterioration of wooden sleepers by applying image processing and deep learning techniques to a simulated under-floor image, which is a projective transformation of images of railway track in front of the train (Fig. 1).
This system can be installed on any train in less than ten minutes, by just setting up a video camera.
It is also less expensive than the under-floor image capture systems currently used by JR companies.

When we applied this system to images of approximately 16,000 wooden sleepers taken from above a train on a commercial line, we confirmed a sleeper detection rate of 99.5% (100% except when the sleeper surface is covered by a significant amount of ballast or other material). A comparison of the degree of deterioration determined by this system and that determined from images (4 levels) by a track maintenance engineer also confirmed that the system is capable of automatically assessing deterioration with an accuracy of 90% or more (Table 1).
In this case, the rate at which bad sleepers (A2, B) were mistaken for good sleepers (C, D) was 7%, but the probability of missing successive defects, which increases the risk of derailment by gauge widening, was considered sufficiently low. With this system, each sleeper is output in a colorcoded format to denote the degree of deterioration, both to a viewer that displays the results and to a tabular inspection record book, making it easy to identify areas where there are successive defects in wooden sleepers.