**4.3 Technical inspection**

Under German as well as most other regulations, it is common to execute a visual inspection together with the brake test. When automating the wagon subsystem and assisting in brake tests, it is important for economic viability to automate or reduce these inspection steps as well.

The approach of W40 is not able to detect


Such failure modes typically evolve slowly since they are related to the wear of the equipment. These failure modes, as well as other slowly developing deteriorations, such as the inappropriate state of the brake blocks, should be addressed by additional technical inspection as opposed to a brake test. In this way, ensuring the brake functionality for the next mission is separated from determining the technical condition of the wagons. Wagon condition monitoring may be automated without large investments into the individual wagons by providing a wayside train monitoring system (WTMS).

In the current state of development, WTMS uses visible light imaging to estimate brake block thickness, and this may easily be extended to detect further visible failures, enabling WTMS to replace most visual checks by human operators [19]. The remaining inspection items such as the closing of hatches, which need to be checked prior to departure, can be automated using cheap and reliable sensors on the rolling stock. The overall system combining an extended network of wayside monitoring with sensible and economical equipment on the wagons is capable of yielding improved safety of the freight rail system at a reduced cost.
