Interesting traffic times; see the full article for some privacy-related considerations
Here’s how they work: Your GPS-enabled phone automatically transmits bits of data to Waze, Inrix, Google and other traffic app makers that show where you are and how fast you’re moving. Some apps also allow users to report accidents, closed roads or construction (when parked or in standstill traffic, of course). Each company then combines the information to get an idea of traffic conditions and distributes that across its network.
Call it crowd-sourcing from your car.