Map out the route you'll be taking to your destination, using an atlas or an online mapping and directions tool like Google Maps or MapQuest. Write down or print out all the highways and streets you will be taking on your trip.
Find the Department of Transportation website for the states where you will be traveling. Most DOTs have a "trip checker" that allows you to check on the road construction projects happening on state highways and interstates. For example, Oregon's "TripCheck" web page includes a map with any road construction projects highlighted, as well as a live camera feed from several traffic hotspots around the state. Note the state road construction sites and determine whether they're on your desired route.
Call "511." This is a Department of Transportation service that allows you call for updates on road construction and delays for various parts of the state from which you're calling. This information can sometimes be more up to date than the DOT interactive maps, because it also accounts for accident and weather delays.
Search the city websites of the places you'll be traveling to find if the local traffic office has any information about area construction. Since the DOT does not manage city streets, it will not have this information listed on its interactive maps. Portland, Oregon's "Keep Portland Moving" site, for example, gives information about delays for inner city drivers.
Change your route if you determine that the roads you chose are either closed or likely to have serious delays.
