Crowdsourced Traffic Data

Could they buy data from Lyft/Uber/etc and cross-check it with their cars' paths?

I think TheOtherHobbes is referring to Google Maps and Waze, not Streetview. Google Maps and Waze, by collecting GPS movements from users, absolutely will learn about light timings, which roundabouts are congested and when, etc. with enough of a sample.

This is exactly how Google maps knows traffic conditions.

Not the raw data, but if you've used Google maps for directions or looked at traffic, then yeah you have.

Google maps traffic data is live

Doesn’t google use waze for data?

The whole business may have changed quite much over there years. Back in the days you had your own people driving around, know you can crowd source quite much of the data collection. When you have the location data for millions of people, you can for example figure out where the roads go, make good guesses about speed limits and figure out one way streets. Points of interest can be mined from web. From search logs you can probably see if you are missing some addresses.

Actually, there is: traffic data.

Feels like a feature Google could make by using the same data they use for traffic monitoring. They know where the train shaped mass of people is.

Waze realtime traffic data was entirely crowdsourced, and probably still is largely so.