I want to know if this account's for 1/3 of the map, that is the sea?

I'm convinced this is a psychological thing. The map feels small because there's so much in it. In Fallout 3 and New Vegas it takes time to travel between significant places and there's significant empty wasteland between those places: this creates a feeling of space. In FO4, in large parts of the map, each location blends into the next because there's no significant empty space between them. With no break, these all feel like one rather small town rather than separate places.

It doesn't help when you can clearly see that locations are close together. Again, in the older games the terrain in many cases helped by preventing the player from seeing just how close some of the locations were to one another. FO4 is so chock-full of stuff that one can usually see that the next significant place is just a few yards away.

The way that Bethesda created the city of Washington D.C. in Fallout 3 also helped in creating a sense of a world far larger than it actually is. By making the player travel through tunnels and metros, the designers created a mental disconnect between the outside city and the inner worldspaces, so that the fact that those worldspaces together actually occupy a greater space than the city isn't at all obvious (just as the cell loading creates a disconnect that allows the interior of a building to be larger than the exterior without it being immediately apparent to the player). Boston removes the metro travel, but as a consequence we now see the city in terms of its real scale, i.e. not very big at all and certainly not remotely the size of an actual city.

In other words, the FO4 map isn't small in absolute terms (for a game), but it's too small for the amount of content. I used to think that Bethesda had been very clever in the way that they designed the Fallout 3 map, but now I'm starting to think it just worked out well through good fortune.

Fallout 4 playable footprint is a little smaller than Skyrim, but a good bit larger than Fallout 3.

It's particularly more dense in downtown Boston.

It's big enough.

Agree. 14 minutes to edge to edge (Vault 111 to the far end of the glowing sea) on foot.

Small or bad desing i don't know... F3 or Skyrimi felt endless walking on varied terrain, with "hidden" treasures (cabins, monuments).

Fast travel is useless because you can arrive to your destinatin within 5 mins. It's just ridiculous.

of course not. if the PC can enter the cell at all it is considered playable.

it also doesn't take vertical play space or larger than normal child world spaces into account either.

http://imgur.com/FppoznP

Based on my observations, fast traveling is actually a lot slower than traveling on the map. Round about 50 or 75 hours of play, on my 2nd or 3rd character I did some comparisons between real time travel (with limited use of sprinting) and fast travel. If memory serves I compared trips between a half dozen locations. It was consistently 2 or 3 times longer on the PipBoy clock to fast travel than it was to jog between the actual locations.

Finally made it to the Glowing Sea last night. Pretty cool. One of the more inhospitable places in a game.

Question: is there a major military base on that edge of Boston in real life? Trying to imagine if they had some reason to think that that side of the city would have been nuked to oblivion or if they just decided they wanted a massive radioactive desert on the edge of the map.

Good point. Lots less having to spend an hour trying to remember how to get up and around on cliff trails. More going where you want and gettin' er done.