Discussion on “Field Test Performance of Noncontact Ultrasonic Rail Inspection System”

In general, the development of novel technology for rail inspection is very welcome indeed. The paper under discussion was well written by the authors. The field investigation results at the Rail Defect Test Facility of the Transportation Technology Center in Pueblo, Colorado are critical for rail inspection management in practice. The discussion paper highlighted previous field experience and findings of rail surface defects. The field experience and some practical findings in this discussion would be useful and should encourage the authors to extend their future research and development with respect to the classification and quantification of rail surface defects in practice.