Private-hire cars have little stickers in their windows - not as obvious as black cabs of course, but there if you look, so they're distinguishable from ordinary private cars. If you mean how to distinguish between Uber and other private-hire cars (since that's what Uber are), I wasn't making the point about mini-cab dangerousness only about Uber specifically. However, the vast increase in danger (as I perceive it) caused by "mini-cabs"/private-hire in recent years has gone along with the increased use of phone apps by mini-cab users, and Uber make up a large proportion of the increase in private hire related to phone apps. Also, car markings, and passenger behaviour at the roadside, helps to distinguish between more traditionally booked mini-caps and app-based ones. Any reference I've made to Ubers specifically might be read as also applying to any similar examples of the apps-driven increase in the number of mini-cabs in London driven by inexperienced drivers.