Where do I find this on my Nex 4000 ?

It says its included/built in.

Partnering with Clear Channel Broadcasting Inc, the built-in traffic tuner provides real-time traffic data for over 90 major cities in North America, including Canada. Check your commute route in advance or re-route to your destination to avoid traffic congestion. There is no subscription cost and no annoying on-screen advertisements. With our traffic tuner, now you are ready to navigate stress-free!

Where do I find this on my Nex 4000 ?

It says its included/built in.

 

Partnering with Clear Channel Broadcasting Inc, the built-in traffic tuner provides real-time traffic data for over 90 major cities in North America, including Canada. Check your commute route in advance or re-route to your destination to avoid traffic congestion. There is no subscription cost and no annoying on-screen advertisements. With our traffic tuner, now you are ready to navigate stress-free!

I suspect it interfaces with Pioneer's external navigation module.

Thought that might be the case, thanks.

the traffic tuner on the 4000nex, is part of the AVIC-U260 nav add-on. It has a separate antenna, I is not a radio station, per say, it is a listing of events in and around the city that may or may not have an influence on your planned route. I was going south on Loop 1, in Austin, and the north lane was closed off with firetrucks and ems. I clicked on the tuner icon, and it was listed on the events list. Traffic was backed up for miles. Glad i was heading south.