As far as 40 goes, you count on most people going to the RTP area for work. I drive in from eastern NC, and by 7:00 traffic is building. Starting about 3:30-4:00 traffic starts backing up as people leave RTP and head east.
Where will you be living and where will you be working? We might be able to give you a better idea of traffic patterns once we know that!
Or you could always check out the traffic cameras posted around town one morning to get a better idea of what you'll be facing
The local WRAL television channel would be a good place to start
http://wral.com/traffic/