## 5 Conclusions  
This study has applied a surface deformation investigation using PSI in six UK study sites to determine the impact that different soils have on the LOS deformation of roads and railways. Sentinel 1 has been shown to be effective at measuring surface deformation of these thin, linear infrastructure assets across a range of environmental settings, thus demonstrating PSI with Sentinel 1's potential for wide scale infrastructure monitoring. By combining PSI outputs with the 1:250,000 scale National Soil Map, this study has identified, in these areas, four major soil groups which pose a ground movement risk to infrastructure networks (Brown soils, Ground-water Gley soils, Pelosols, and Surface-water Gley soils). These soils are characterised by seasonal waterlogging. The change in soil moisture is associated with volume change in clay soils. Minor and major roads showed a similar response to soil movement, whilst railways appeared to act independently, particularly when over Peat soils. Podozolic soils remained stable in this stud--for all infrastructure classes investigated--due to the permeable nature of these soils over freely draining bedrock. Further investigations are required to determine the response of Lithomorphic soils, as the results were inconclusive due to the broad taxonomic nature of this group. Major soil groups in this study can contain numerous soil series, with many different soil textures and properties. This can lead to differential ground movement even within a classified major soil group. The use of higher resolution soils data will help better explain observed deformation trends. Re-running the PSI analysis with a higher resolution soil map would allow better characterization of the observed movements to individual soil series. Furthermore, inclusion of a higher resolution DEM (such as Shuttle Radar Topography Mission (SRTM) 1 Arc-Second Global) would also help achieve better correction in the geocoding stage. The inclusion of new Sentinel 1 data to increase the length of time series would also be highly beneficial to reveal long term trends soil-related infrastructure deformation. Furthermore, a comparison between PSInSAR and other techniques such as the Small BAseline Subset (SBAS) [30] and Intermittent SBAS (SBAS) [31] would help to further establish the suitability of these techniques for wide scale monitoring of infrastructure deformation. SBAS and ISBAS generate near continuous coverage of ground deformation measurements, even over vegetated areas. This could help to better identify surface deformation phenomena occurring adjacent to linear infrastructure assets, which have the potential to cause a long-term risk or embankment failure. In the absence of In-Situ levelling data, a validation site was established within a disused quarry in Dartmoor National Park, England. The results from this exercise returned the expected result of an associated error of \(\pm\)1.5 mm, which suggests a good performance of the Persistent Scatterers Interferometry technique investigating soil impacts on infrastructure. This work contributes to an increased understanding of the risks posed by soil movement to infrastructure networks in the UK. It has helped to quantify relationships between infrastructure movement and major soil groups. This is critical for the planning and monitoring of large-scale infrastructure projects such as the UK's planned High Speed Rail 2, for which an understanding of the soil-related risk is key to the success of the project. This paper has demonstrated the potential of PSI and Sentinel 1 to be used as a tool for remotely monitoring environmental risks to transport infrastructure networks. This work was supported by the UK Natural Environment Research Council [NERC Ref: NE/M009009/1]. Costs for open access publication are provided through Cranfield University via the RCUK block grant. The authors would also like to acknowledge the Centre for Ecology and Hydrology (NERC) for providing meteorological data. All authors made significant contributions to this work.