Simply pick a day of the week and a time, and Google will color the map to show typical traffic conditions on that day/time. There are a few oddities I found in it, but it’s a neat idea. For example, here it Atlanta at 5am on Sunday:
What’s up with the heavy traffic on 400? While there might always be an accident somewhere in town, the predicted traffic for that time of day should be all green.
All in all, it’s a neat idea. Here are a few pictures that walk through a Monday morning rush hour (5am-8am):
It shows conditions slowly getting worse, which is exactly how things go at that time of day.
My main concern lately with Google Maps traffic is the sporadic coverage. One day they’ll have almost everything covered, and the next day there will be gray sections everywhere. I’m not sure where they get their data from (and it may not be their fault), but the lack of consistency makes the service far less useful.
That being said, after e-mail and web browsing, Google Maps traffic is the killer app on my cellphone. I use it a lot. This new feature isn’t on the mobile version yet, but I don’t care if it makes it there or not. When I’m checking from my phone, all I need are live conditions. If I want to look at predicted traffic for another day, I can do that from my PC.