I have been looking at the wait times on the Dulles web site:

http://www.flydulles.com/iad/security-information

I shows security wait times like 5 minutes for the East Checkpoint and 1 minute for the West Checkpoint. At 4:00 PM on a weekday.

Is this site accurate?

I rarely use IAD but from personal experience at other major US airports, security wait times are never that short on a weekday afternoon at 4:00 PM