UK: In response to a request from infrastructure manager Network Rail, Product Innovation has developed a void meter designed to measure the movement of a rail or sleeper in real time, enabling maintenance crews to attend only when needed.

The Void Meter is physically and electronically simple to install, with all mechanical and electronic components contained in a robust metal casting. A moveable stainless steel rod is sprung downwards towards the sleeper or rail, and moves as a train passes. The vertical position is measured using a Hall Effect microchip within the casting, meaning there is no physical connection between the mechanics that move the vertical rod and the electronics. This makes the product immune to the effects of weather and vibration. A 4 to 20 mA signal is output to a data logger and remote monitoring equipment in real time. The Void Meter has a measurement range of 100 mm, and resolution of 0·5 mm.

Network Rail is using the prototypes to assess how best to use the devices, whether standalone or in combinations at turnouts and crossovers.