70 minutes to connect, and switch airports besides? Not a chance.

traffic is not a simple good/bad, it depends on wx and all kinds of things but in general its crowded on the roads. while you'd be travelling "opposite" rush hour (and yes, rush hour starts just after 3 these days), the thing about this area is that there really isn't any difference between travelling "opposite" rush hour and with rush hour these days.

BTW, the hour to travel using public transportation was a surprise to me. although that will depend on the timing of your arrival and connections (bus to metro), etc but if you could do it in an hour, that's great.

If you could pull that off you could probably win the $1 million prize on the Amazing Race.

I would say next to impossible. Even if you cabbed it, it would take all of your connection time to get to DCA, much less clear security and check-in. No matter how fast you run, it will take you at least 15mins to get to the curb at IAD, another 45mins to speed like a bat out of hell to DCA (and it will take you longer at that time of the day), which will leave you arriving at the gate just as they are closing the doors. And that's assuming perfect travel conditions in the skies and on the roads.

Chances of hitting the Powerball are higher, me thinks

But as an FYI: The cab from IAD-DCA will set you back about $60 when you factor in the tip. You will hit some congestion at the merge of the airport road (VA267) and I66, at the merge of I66 going on to 110, and pretty heavy stuff on Route 1 (may be better to jump on GW Parkway). 45 minutes minimum in ideal conditions.

If it is possible to be more pessimistic than blueDC, I will provide that pessimism. Completing this connection in the 70 minutes required is impossible. There just isn't enough luck in the world for eveything to line up to make this connection, unless your into flight into IAD arrives early, and your flight out of DCA closes the door late.

Everything must be perfect in both airports as well as on the roads. That just isn't going to happen.

Point taken folks. This idea is still-born. I will look at other options

And the taxi drivers just went on their 5th strike. Just like Italy & France.

Looks like I'm going to need to do IAD-DCA in February. In addition to the above options, has anyone tried SuperShuttle? It looks like $23 direct.

SuperShuttle can be a good option. Just hope that they don't decide to do too many drop-offs and pick-ups in between IAD and DCA.

Not a chance... not even by cab. You would need to go from concourse C at IAD to the main terminal (10 minutes) then onto the cab stand. If your lucky you get one of the washington flyer cabs quick. Then it is a 30 mile drive between IAD & DCA (not to mention a $50 cab ride). The timming of your flights is bad as well -- being right in the middle of rush hour. The route to DCA will take you on congested I-66. You'd be extremely lucky to make the connection with a 2 hour window.

the thing about supershuttle that I didn't like and stopped me from using them the one time I was going to was that they had no estimate of any sort as to when the shuttle would leave. If you have enough time to wait 30+ minutes for a departure, then it's a good, reasonably priced option but if your time is shorter, I don't recommend the option unless the shuttle is pretty much pulling out as you come up to the counter.

Thanks. I'll probably take one of the buses to the Metro.

Just an update. I took the Washington Flyer bus to the metro, then took the metro to DCA. Worked great. Thanks for the tips.

that made me burst out laughing