MickeysMonsterMom -
When you start to get closer to the DC area, you should tune the car radio to 630 AM and/or 1500 AM. These are the two major news/talk radio stations in Washington. If there's any bad traffic or accidents ahead, they'll let you know plus they have regular weather/traffic reports.
I agree with caitycaity that I-81 probably takes you out of your way.
It's a shame that everyone, except the driver, will probably sleep through the US15 section of your trip...that part can be really pretty, *especially* if you kept on 15 south of I-70 crossing the Potomac at Point of Rocks(?) passing close to Balls Bluff National Cemetery (the smallest National Cemetery in the country) down to US50 or to I-66...I think sometimes that those farms on 15 are many horses' ideas of Heaven.
I have lived in the DC area for 20+ years, in Northern Virginia for most of that time. If you're coming through on Saturday, your plan to start out around 4am/5am from Gettysburg sounds good. Saturday traffic getting through the "Mixing Bowl", aka the fabled Springfield I-95/495/395 Interchange, can be a b*tch, even on the weekends (though as another poster said, since one of the flyovers has been installed the traffic doesn't seem as consistently bad as it used to be). At least we have three lanes between DC and Richmond now...I remember when it was two....ack. Even so, most folks coming through here are mostly concerned about the traffic around the Beltway, when the traffic south of DC, from about Woodbridge(Route 1 Interchange) to Fredericksburg can be equally a pain.
Have a good time - you're goin' to DISNEY!!!!
agnes!
Just remember...
'All I Needed to Know About Travelling I Learned from My Time at WDW'.
In other words -
"What have we learned from our time at WDW, Class?"
"We have learned to get up early to take in as much of the parks as we can, to avoid the WDW visitors who get there at 11am and wonder why it's crowded."
[The above can just as easily be applied to Interstate roadtrips through & around the nation's capital.

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