Thermit (GB) has a lot of experience monitoring different rail characteristics, one example of this is the Hensall project.
The Hensall project was to monitor stress free temperature, rail temperature and longitudinal movement at breather switches on the Wakefield to Goole line. This was as it was noticed that the track bed was dropping causing stress in the rails, due to coal extraction happening below the track.
To help monitor the stresses, temperatures and movement at the expansion switch a multi-step method was used. This was done so that reactive measures could be taken. The first solution was to install a series of vibrating wire strain gauges to the rails. The second solution was to install a series of linear displacement potentiometers across the breather switches.
The series of vibrating wire strain gauges allowed the strain and rail temperature data to be monitored. The data was then transmitted to servers located at a GPRS track-side collection station. With this data collated in a single location, thresholds could be set to trigger, notifying an operator, if these thresholds were reached so that preventative action could be used.
The series of linear displacement potentiometers allowed monitoring of the relative movement at the expansion joints and the supporting sleepers. This meant that that the breather switches could be maintained to operate within the required limits.
This solution fulfilled all customer requirements and is still in current use.