SOUTH AFRICA: Underwater sonar has been adapted for remote rail defect detection by South Africa's Council for Scientific & Industrial Research and the Institute for Maritime Technology.

A transducer bolted to the rail creates ultrasonic vibrations which propagate up to 1·5 km, and an electronic sensor sends alerts to the control room if the signal is not detected.

It warned of two rail breaks and thus prevented potentially costly derailments during a year-long trial on South African freight operator's Transnet's Sishen - Saldanha heavy-haul ore line where temperatures range from -10C to 50C. It has also been tested in Canada, on the New York subway, in Hong Kong and in Japan.