Climate change and the increasing use of public transport has put further strain on the UK’s railway network, with over 100,000 trains affected by 938 separate rail issues in 2023 alone. However, by using modern technologies and monitoring, we can help to turn this statistic around. Here, Dave Bradshaw, our Monitoring Manager, explains how monitoring can play a part in this.
Network Rail announced its plans for Control Period 7 (CP7) last year, with a significant proportion of this period’s funds being allocated to maintenance and renewals. We can expect the focus to be on creating new services, as well as maintaining and improving existing tracks. Monitoring will form a large part of this effort, ensuring not only the safety of those carrying out the work, but also the passengers and staff who will be travelling on the lines following project completions.
Network Rail’s ‘Boots off Ballast’ campaign will also be a key influence, focussed on reducing the number of site personnel working on or around live tracks. Traditionally, track monitoring has involved manual surveyors visiting sites in person and working trackside during possessions. As well as putting them at a higher risk, it can also have a high-cost impact to the contractor.
To ensure the safety of the trains, passengers and construction workers, any activities being carried out adjacent to a live track must comply with the Network Rail track monitoring standard NR/L2CIV/177. These standards state that the track geometry must be measured at three metre centres across the zone of influence (work area) and at 30 metres outside of the zone of influence. This track monitoring offers assurance of any changes to track geometry and detects any changes that fall outside the allowable movement criteria, set as part of the monitoring track plan – an essential requirement for contractor’s works.
Measuring track geometry is based on changes to the following parameters: Cant, Twist, Vertical Fault and Alignment Fault. As part of the monitoring track plan, the risk will be assessed in accordance with NR/L2/CIV/177 to determine the frequency of the readings, as well as the type of track monitoring required.
So, what solutions are available that can automate track monitoring, reduce boots off ballast, improve safety and minimise costly rail possessions?
Optical Instruments
The optical method uses Automated Total Stations (ATS) to measure the relative change in track geometry.
Track monitoring prisms must first be installed on both running rails at three metre intervals, in accordance with the NR/L2/CIV/177 standard. The total station will then be mounted in a suitable location with a good line of sight of all the monitoring prisms and programmed to measure 3D movement of the prisms at the required frequency.
The limitations on the frequency of reading will be subject to the quantity of the prisms the instrument needs to measure - at best, the ATS can measure at 30 minute intervals. If there are a large quantity of prisms to measure, then multiple ATS systems can be linked together to form a network.
While similar to the traditional manual surveying, the frequency of readings can be extensively increased with this solution, allowing for changes in track geometry to be measured throughout the day and any issues to be detected far earlier. There is also no need for track access to manually take the readings, improving safety and reducing overall costs.
All generated data can then be uploaded to a web portal, ready for review by the contractor and stakeholders across the duration of the project.
However, there can be some limitations to this type of monitoring technology, with the potential for a total station’s ‘sight’ to be affected during poor weather spells, such as fog or heavy rain, and on tracks that change direction too severely.
A great example of this equipment in use is on the repair works to South Tyne Viaduct in Northumberland, where Mabey Hire’s track monitoring was implemented by main contractor AmcoGiffen to gather information on track displacement and movement. Total stations formed a critical part of this scheme, with the jacking works being carried out under the structure, it was essential that the track geometry was measured constantly throughout the duration of the project.
Wireless Tilt Sensors
Another option is Wireless Tilt Sensors, which can be used to monitor relative track changes for Cant, Twist and Longitudinal Profile. These are installed directly onto the sleeper rails, again at three metre intervals in accordance with the NR/L2/CIV/177 standard.
Not only does this type of monitoring measure every piece of data remotely and regularly, but it does so to an even higher degree of accuracy than total stations. The sensors also aren’t affected by poor weather or track direction.
Story Contracting recently liaised with Mabey Hire’s monitoring team to install such bi-axial tilt sensors onto the sleeper rails adjacent to its work site, when performing repairs to gabion walls around the River Garry in Scotland. With data fed back to the contractor in real-time from Mabey Hire’s Insite portal, they benefitted from an early warning system should their works begin to infringe on pre-agreed deflection tolerances.
While tilt sensors can present a higher upfront cost, with more labour time required to install them, they do provide longer-term cost savings. Once installed, they can be handed over to the lead contractor to independently manage, coordinate and monitor the data they collect.
The sensors are also able to be safely left on the track even after work has finished, continuing to collect data as the network is reopened to trains. Here, the use of monitoring shifts to become an early warning system, should there ever be any future changes in the track geometry that would require remedial works.
It is clear that, through the use of automated track and trackside monitoring systems, those in the rail sector can not only prioritise health and safety but also receive more accurate data on the condition of their assets. With a wealth of experience in assisting construction works across the rail sector, Mabey Hire has a range of monitoring solutions which can be implemented into regular maintenance or improvement projects, ensuring both the rail network and those working on it are protected.
