The Maps app packed into Mavericks isn't exactly overwhelming with features, but that doesn't mean it's not useful. OS X Daily points out that it includes a traffic indicator that you might have missed.
In the top left corner is an icon with a little car on it. Turns out that icon turns on the traffic indicators that show road congestion, incidents and other causes of slow moving traffic. It will also show you were construction is, where roads are closed and more.
If you've never noticed it before, try it out the next time you open Maps on your Mavericks machine.