Cool new (for me) Google Maps feature: Traffic conditions on Surface Streets

[SDGuy]

I've gotten used to using Google Maps to check highway traffic conditions. It looks like in the past day or so, they've also added surface street traffic (at least for San Diego-YMMV), something Caltrans doesn't even show. In the below screen capture, the thin lines are all surface streets around the San Diego region. I have no idea what they're using for data sources, but I won't complain (as long as it's accurate).

Edit - looks like they've been at work on adding this since August. They must have just recently got to San Diego.