 Mitigating the effect of linear transport infrastructure (LTI) on fauna is a crucial issue in road ecology. Wildlife crossing structures (tunnels or overpasses) are one solution that has been implemented to restore habitat connectivity and reduce wildlife mortality. Evaluating how these crossings function for small wildlife has often been recommended but, mainly due to technical limitations, is not often conducted in practice or only as short-term monitoring (less than 1 year). In this study, we developed and tested an automated device that records the detailed behaviour of animals when using wildlife tunnels. The method is based on marking and detecting individuals with RFID (radio-frequency identification) tags and allows small animals to be tracked. Composed of four antennas (detectors) placed at roughly 2 m intervals, the system was tested in a tunnel in northern France in the summer of 2017. One species of amphibian (the toad Bufo spinosus, n = 13) and two carabids (the ground beetles Carabus coriaceus and Carabus nemoralis, respectively, n = 3 and n = 4), marked beforehand with PIT (passive integrated transponder) tags, were recorded when they crossed these detectors. This allowed individual trajectories, including crossing speed, to be estimated.