Thank you for sharing this. As @emvee pointed out and as listed in the documentation, GraphHopper was used to match the TomTom GPS traces to the road network. I can imagine some of the false positives stem from this process, especially given unorthodox movements some carriers of TomTom GPS logging devices may exhibit (e.g. movement against driving direction). A huge step would be if TomTom open sourced (part of) these anonymised GPS traces to the (research) community, such that we could run our own map matching algorithms and routers against the data and come up with even more valuable insights into the quality of the OSM road network (I would personally be very interested in this since I have done map matching experiments against the OSM road network in a research setting in the past). Perhaps it would even be possible to launch a Kaggle challenge with a subset of the TomTom GPS traces, divided into a test and train set, in order for the larger community outside TomTom to come up with the best possible way of using this data to find potential improvements in OSM. Would love to hear your thoughts on this!