Field test performance of noncontact ultrasonic rail inspection system

This paper presents the latest results from a noncontact ultrasonic rail inspection system developed at the University of California, San Diego (UCSD) under the auspices of the Federal Railroad Administration. Noncontact rail probing is an attractive feature that could potentially allow for new possibilities. The UCSD system utilizes a focused air-coupled transmitter, symmetrically placed air-coupled receivers, and a real-time statistical algorithm to maximize true outliers (defects) and minimize false positives. Two field tests were conducted at the Rail Defect Test Facility of the Transportation Technology Center in Pueblo, Colorado, at test speeds from 1.6 to 24 km/h (1 to 15 mi/h). The results of these tests, evaluated in terms of probability of detection versus probability of false alarms (receiver operating characteristic curves) indicate a good detection performance at the speeds of 1.6 and 8 km/h, with a much poorer performance at the speeds of 16 and 24 km/h. Possible reasons for the performance degradation at the higher speeds are discussed, and future work aimed at mitigating these issues is proposed. (C) 2017 American Society of Civil Engineers.