Google Maps offers a lot of crowdsourced information. Some of it is based on user input and some other info is calculated automatically by Google's algorithm, such as the crowdedness of an attraction, difficulty to find parking, and more. While it's relatively easy for an algorithm to tell if you'll face traffic on your drive — and with decent accuracy — it's much more difficult for it to know if your underground subway will be crowded or not. You need a reliable source for that info, and Google seems to be working on that.

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