eli5 How does google maps show traffic congestion in real time? (and other related questions)

Question

1. Do they use satellite images?
2. are there other services that do the same thing?
3. How do they get the data about public transits?

In: Technology

Answer 1

From other devices. That’s why there was a guy (might have been here in Australia but can’t remember) who altered traffic conditions by riding a bike with a hundred phones in a basket. Google saw it as congestion, started advising people to avoid the area.

Edit: it was in Germany and he was walking, but the point stands. He was an artist, and walked it past the Google headquarters over there.