Apologies if this has been covered before, but, what's the voice (?) or any other command to show XM traffic?

 

It has to be available for your city. But if you have it, say, "Display traffic incidents". This will show real time traffic (if you have it in your city). You can also say, "Display traffic speeds", which will show traffic in red, yellow, green (like a traffic light). Green is free flowing traffic. Yellow is fairly conjested traffic and red is bumper to bumper.