The use of spatial and temporal analysis in the maintenance of road mortality mitigation measures for wildlife in Ireland

Abstract: Urbanisation and a growing global population have caused our road networks to expand rapidly in the past decades. The consequences of transport infrastructure for wildlife include traffic mortality, habitat loss and habitat degradation and the negative impact of a road extends far beyond the road itself. In Ireland, there are mitigation measures for wildlife mortality in place on all major roads. Mitigation measures can help reduce wildlife-vehicle collisions and increase habitat connectivity but need to be properly monitored and maintained following implementation. This study was carried out in collaboration with the Environmental Policy & Compliance department at Transport Infrastructure Ireland (TII), a state agency in Ireland responsible for national road and public transport infrastructure. It applied various spatial and temporal analyses methods in order to ascertain how best to prioritise critical road sections and times for maintenance. The significance of the study is that recent site visits carried out in Ireland found that 66% of mitigation measures were of inadequate standard. The methods were applied to roadkill data taken over an eight year period on the M3 motorway in county Meath, Ireland. This case study was chosen as mitigation measures, such as underpasses and mammal underpasses, have been in operation since its’ opening in 2010. It was found that temporal analysis could provide an insight into whether roadkill was increasing or decreasing annually as well as what months were most recommendable to carry out maintenance. The spatial analysis began with using Ripley’s K-statistics to first determine whether or not clustering of roadkill was occurring along the study area. Four different methods of locating hotspots along a road network were then applied and compared; Malo’s method, 2D Hotspot Analysis using Siriema Road Mortality software, kernel density estimation using SANET and finally KDE+. The findings showed that, despite mitigation measures being in place, hotspots were still occurring indicating road sections experiencing higher numbers of roadkill than expected in a random situation. These sections could then be prioritised for maintenance. It was found that the KDE+ software in conjunction with the use of a roadkill data app was the most recommendable approach. It was also noted that that the app should be expanded to other road classes and rail. It is recommended that this be made a standard protocol, comparable on a national level, for the prioritisation of mitigation measures for maintenance. Finally, it was recommended that more public awareness about wildlife-vehicle collisions and mitigation measures be raised. In the future, the app could also be connected to GPS systems to warn drivers of critical road sections. If these methods and recommendations are applied to the Irish road network, a reduction in roadkill should be observed.