Per chat with @jcsg, I briefly tried the LocalOutlierFactor model. Posting early, will spend some more time for a detailed analysis of both the model and the results.
Per https://stackoverflow.com/a/36869611/3453958
The NearestNeighbors class is unsupervised and can not be used for classification but only for nearest neighbor searches.
Neighbors for an inlier (good highway)

Neighbors for an outlier (harmful highway)
