You can learn a lot about people from the gadgets on their person, history has taught us, and that includes their movements. In a paper published on the preprint server Arxiv.org Wi-Fi has a number of advantages over commonly used modality classification schemes, the researchers point out. It's ubiquitous, for one, and it works reliably indoors even in "challenging" environments like urban highrises. "Due to their … pervasive nature, Wi-Fi networks have the potential to collect large-scale, low-cost, and disaggregate data on multimodal transportation," the paper's authors explained. "In this study, we develop a … framework to utilize Wi-Fi communications obtained from smartphones for the purpose of transportation mode detection."