> Then both in terms of any arbitrary area in the US or any arbitrary city in the US, it's unusually dense (much more dense than the mean density.)

I haven’t visited DC so I’ll have to take your word for it. But it should be noted that I can’t find anything online that supports yours assessment of DC being unusually dense.

And even if it is, that just makes a stronger case for the need of better public transport services.

> Many places in the US have these and both DC and the suburbs around it are full of them.

I’m sure they are but having a park and ride scheme is only of benefit if you invest in public transport, which, by your own admission, DC doesn’t.