A Guide to Track Movement in Rail
Safety
Impact of Infrastructure Failures
Infrastructure failures, such as track defects, signalling errors, or structural issues, can lead to accidents with severe consequences. For instance, in 2007, the Grayrigg derailment in Cumbria resulted from a faulty set of points, leading to the death of one passenger an injuries to several others.
Weather-Related Risks
According to the Federal Railroad Administration (FRA), weather-related incidents accounted for approximately 9% of all train accidents in the United States in 2020.
Importance of Maintenance
Regular maintenance of infrastructure is essential for ensuring safe operations. According to Network Rail's Infrastructure Management Statement, published in 2020, the organisation invested £4.1 billion in maintaining and renewing railway infrastructure across the UK, reflecting its commitment to safety and reliability.
Aging Infrastructure
Aging Infrastructure
Over 40% of Australia's rail infrastructure is more than 50 years old; for a portion of this infrastructure, the assets have surpassed their intended lifespans (Infrastructure Australia).
Maintenance Backlog
Years of underinvestment and deferred maintenance have led to a backlog of maintenance and renewal tracks across the railway network. Network Rail's own data indicates that as of 2021, there was a backlog of 31.5 billion in track renewals alone, highlighting the scale of the challenge.
Disruption Impacts
In 2020, delays on Class I freight railroads alone resulted in an estimated economic cost of over $2.5 billion. This includes costs associated with lost productivity, additional fuel consumption, and missed delivery deadlines for goods transported by rail (Federal Railroad Administration, USA).
Functionality of Service
Performance Targets
Network Rail sets performance targets to measure the punctuality and reliability of train services. In the UK, punctuality is typically measured by the Public Performance Measure (PPM), which assesses the percentage of trains arriving at their destination within a specified time window. According to the Office of Rail and Road (ORR), the punctuality target for passenger trains in 2020-2021 was 92.6%
Infrastructure Failures
Infrastructure failures, such as track defects, signalling failures, or overhead line faults, are mong the leading causes of train delay. According to Network rail's own performance data, infrastructure-related incidents accounted for approximately 60% of all delay minutes in 2020-2021.
Cost of Delays
Rail delays can cost the Australian economy an estimated AUD 1.4 billion annually in lost productivity and additional expenses (Australasian Railway Association).
Satellite Remote Sensing
Radar Imaging
Satellites equipped with synthetic aperture radar systems emit microwave pulses towards the Earth's surface. These pulses penetrate through clouds, vegetation, and other surface obstacles, allowing the radar to capture images of the ground regardless of weather conditions or time of day.
Interferometry
InSAR relies on a technique called interferometry, which involves comparing radar images of the same area acquired at different times. When two radar images are acquired, the slight differences in phase between the radar waves reflected from the ground are measured.
Phase Differences
Ground movement, such as subsidence, uplift, or lateral displacement, alters the distance travelled by radar waves during the time between image acquisitions. This results in phase differences between the radar images that can be measured and used to calculate the extent and direction of ground movement.
Early Detection of Ground Movement
InSAR technology enables continuous monitoring of ground movement along railway lines. By detecting even subtle changes in terrain elevation or displacement, it can provide early warning of potential hazards such as landslides, subsidence, or ground instability. This early detection capability allows railway authorities to take proactive measure to mitigate risks, such as reinforcing embankments or implementing speed restrictions in affected areas, thus reducing the likelihood of accidents and ensuring passenger safety.
Identification of Defects
InSAR analysis can detect deformations or settlements in railway infrastructure, such as tracks, bridges, and embankments, which may results from aging or structural deterioration. By identifying these defects early on, maintenance crews can prioritise repairs and upgrades to address critical uses before they escalate into safety hazards or cause service disruptions. his proactive approach helps to maintain the integrity of the railway network and minimise the risk of accidents due to infrastructure failures.
Optimisation of Maintenance Activities
InSAR data provides valuable insights into the condition of railway assets, allowing infrastructure managers to optimise maintenance activities and allocate resources more effectively. By identifying areas of high risk or deterioration, maintenance schedules can be adjusted to focus on critical sectors of the network, reducing the likelihood of unplanned downtime and minimising service disruptions. This proactive maintenance approach helps rail infrastructure to meet performance targets by improving asset reliability and ensuring punctual service for passengers and freight operators.
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