The following thread will be how to access Tatsumi parking area in eastern Tokyo.
Directions will be from Yokosuka (via Daikoku Futo) followed by directions from Yokota AFB.
Yokosuka (via Daikoku) to Tatsumi parking.
There are two routes to Tokyo from Daikoku Futo parking. The Yokohane and the Bayshore Route.
The Bayshore route is the one that runs closest to the eastern coast of Japan from Yokohama to Tokyo. It's the easiest way as it's the most direct. You'll want to take that route. On the above map, it's the bottom most route highlighted.
Make sure you follow the signs when leaving from (if from Daikoku) and take the route for HANEDA AIRPORT.
Once on the Bayshore route, follow it all the way to and past Haneda Airport.
In the above picture, you'll notice that there is a junction (in light blue) to go from the Yokohane to the Bayshore route. If you must come via the Yokohane, DO NOT miss this junction or you'll not be able to easily get to Tatsumi parking area.
There will be a toll gate about 5k past Haneda airport on the Bayshore, and about 2k or so from the junction from the Yokohane to Bayshore. Shortly after the toll gate, you'll go into a fairly long tunnel. When you come out of the tunnel, you'll be in the Odaiba area.
NOTE:There is an active speed camera right in front of the Fuji TV building just before the Rainbow bridge exit. Watch your speed here. There is also one after the Rainbow Bridge junction, but not sure if it's active or not.
You'll continue past the junctions for Rainbow Bridge (Expressway 11) and Toyosu (Expressway 10). Once past those two, quickly get into the far left lane. This lane is an exit lane for the junction you want (Expressway 9).
Once on the inclining ramp, you'll notice Tatsumi parking on the right.
You've arrived!
Yokota to Tatsumi Parking area
From Yokota base, you'll want to head to the Chuo Expressway (Highway 4) via Hachioji and head towards Tokyo.
From Hachioji junctions, it's pretty straight forward to Tokyo.
Once you get close to the C1, you'll see a sign that will tell you which lane you'll need. You're going to want the right lane. You can see the sign for Rainbow Bridge.
You'll enter a tunnel before the actual split, which is where the Chuo ends and you are now on the C1.
NOTE: Be sure to follow the signs to stay on the C1 as there are a few points you need to pay attention so as not to accidentally exit.
You now want to take the C1 to Rainbow Bridge.
When you take the exit for the Rainbow bridge route, stay in the left lane. You'll exit right with a slight incline and then a long sweeping right bend that straightens out. You'll be coming up to a very weird junction. The two left lanes are for rainbow bridge, the two right lanes will be for the Yokohane expressway towards Yokohama. STAY LEFT!!!
After you cross Rainbow Bridge, it's a downward left bend followed by a long sweeping right bend.
After the long sweeping right, you can be in either lane as the two lanes will actually exit to the left at the Bayshore route. The two lanes will merge into one and that lane will be the lane you want to stay in.
You'll pass the junction for Toyosu (Expressway 10) and take the next exit for Expressway 9. You'll see Tatsumi parking area on the right.
You've arrived!
Entering Tatsumi is pretty easy. The entrance is on the right of the exit ramp from the Bayshore route. You come in and there will be about 20 or so parking spaces on the front side or you can swing around the back side for more parking. Notice the layout of the arrows on the map.
I hope this helps.