I need to make a 730pm flight on a thursday from BWI.
I work in bethesda and thought it would be nice to just drive....what time should i leave?
or is is better to go back to DC via metro and get to BWI using public transp.?

I'd say hit the road by about 5:00 if you want to drive. Otherwise, public transportation is the way to go, though that's not simple, either.

You're taking a big risk on traffic. If all goes well, you should be in the airport parking lots within an hour or so. But heavy rush-hour traffic (which is the norm) will add 3045 minutes to the ride.

You seem amenable to public transit. The cheapest way is taking Metro to Greenbelt and then the B30 Metrobus. That avoids the Beltway traffic jams, but you are still susceptible to traffic issues on I-95.

Best way is take Metro to Union Station, and then the Marc train to the BWI station. Shuttle bus than takes you from the BWI rail station to the airport terminal. Amtrak trains cover the same route, but costs about 3 times as much as Marc commuter train. Either way, you still need to allow time for the bus-train-bus - but you shouldn't encounter any traffic problems this way.

thanks
i just moved to the dc area and have no idea what the rush is like....so I didnt know what sort of driving times are normal
is the shuttle from the station (amtrak/marc) to the terminal pretty regular?

A' that makes close to 2 hrs. i think over an hour and a half.
B. I think the M30 runs BW parkway. no better. still an hour and a half. maybe more, because metro to dc from bethesda and back out is not a 10 min ride.
c. i have never timed this, but i would bet on over 1.5 hrs.

i would recommend drive the beltway. plan to start north on I95, but cross cross over to BW pky if it is screwed up real bad. you can cross at md 32 and i195, or just continue to beltway to bw pky.

this is not a nice rush hour trip. i have only back commuted this trip. the backup starts by 330pm.

the beltway could be a disaster...it's all hit or miss. and public transportation isn't really that hard. metro to union station, and pop in $6 for a marc ticket to bwi station. i find it the easiest way to get to BWI from DC.

Yes, the shuttle runs on a regular basis. I don't have the exact number (check the bwi website), but it's probably every 10 minutes during peak times.

Here's a link to the Marc train schedule serving Union Station to BWI:
http://www.mtamaryland.com/services/...N_HTML_New.cfm

There are a few "choke points" where I-95 slows down a bit, but as a daily commuter on that route, it's more frustrating than anything else and even during rush hour you can drive from Bethesda to BWI in just over an hour depending on where you're coming from exactly. Sure there "could" be an accident, the same possibility as on any other road...

Leave at 4:30, you'll be at BWI by 5:45, plenty of time.

Even though ColumbiaPete is correct and theoretically I should be able to leave my project at Tyson's at 4PM to make a 730 at BWI, it certainly is not guaranteed and I have gotten religion and now avoid the stress, no matter how cheap the fare.

But then again, I am on the wrong side of one of ColumbiaPete's "choke points," the 270 split, and although it should only be an hour an a half for me, it once was an hour more than that.

Since the car rental drop for BWI is now in Delaware (well anyway, it seems to be), it just does not compute for me to drive up there after work.

Just be aware that a Metro trip from Bethesda to Greenbelt (with a transfer from Red to Green Line at Gallery Place) on a rush hour schedule takes at least 50 minutes on its own.

Go Greenbelt to B30 if you want to be really cheap, but MARC train there probably makes the most sense.

If you drive, the BWI buses from the outer lots can be slow. Daily and Express lots are a bit faster.

I do this commute in reverese, but even if you are checking bags and parking far out, you should have plenty of time if you leave at 4:30.

The MARC train that stops at Greenbelt is on the Camden line and doesn't go to BWI at all. You would need to get to Union Station in Washington and catch the Penn line MARC to get to BWI.

madecon is referring to the B30 express MetroBus that goes from Greenbelt Metro to BWI. It's a great option during non-peak hours, but I would take MARC from Union Station since you don't have to deal with traffic issues.

Then I would leave it to madecon to say why "the MARC train from there probably makes the most sense.". madecon, are you suggesting a drive from Bethesda to Greenbelt, then a MARC train to Washington to transfer to another MARC train to BWI??