Google Maps finally rolled out its upgraded traffic features to Toronto earlier this spring, which means those cruising across the city in cars can see estimates of how long their journeys will take based on current traffic conditions. How does it work? Turns out all those drivers using Google Maps on their phones (with the GPS enabled) are automatically sending anonymous data back to Google showing how fast they’re moving. Compiling that data from thousands of users, the company gets an idea of live traffic conditions. When you search for directions, Google Maps will tell you how long it will likely take to get to your destination—and whether it would be faster to take the subway instead.