Depending on where exactly in RTP you are heading, and where in Youngsville you are driving from, you should be able to make it to RTP in 40-45 minutes, even accounting for rush hour.
One option is to take US-1 South to Hwy 98 West. From Hwy 98 West, you have several choices:
- Hwy 98 West to: right on Creedmoor Rd.; right on I-540
- Hwy 98 West to: left on Old Creedmoor Rd (it will turn into Carpenters Pond eventually); right on Leesville Rd; left on I-70; right on Page Rd.; left on TW Alexandar Dr.
- Hwy 98 West to: left on Sherron Rd. (turns into Miami Blvd). You will eventually cross over I-70, and Miami Blvd. will intersect TW Alexander Dr.
From what I've read, the first two seem to be more popular with folks who commute from Wake Forest as some have stated that Miami Blvd. can get rather congested during rush hour.