Highways and Rapid Transit: Should They Go Together?

Today on the Streetsblog Network, we've got a something of a debate going on the subject of putting new transit routes alongside highways in American cities.

Last Friday, Yonah Freemark at The Transport Politic noted the opening of Portland's Green Line with a post titled "Portland's New Rail Line Is Welcome News, but It's Not Routed as It Should Be." The line's location on the highway right-of-way, argues Freemark, will discourage transit-oriented development:

Transit and freeways side by side in the upscale Charlottenberg neighborhood of Berlin.

But that's not how Jarrett Walker over at Human Transit sees it. Walker pulls out some pictures from a recent trip to Berlin to make his point. There, he notes, thriving upscale neighborhoods like Charlottenberg can be found on precisely this type of transit/freeway corridor:

When a New World city builds a rail line alongside a freeway, or
even in its median, nobody expects the result to look like Berlin any
time soon.  But it's not obvious that these can't be dense
transit-oriented districts in their own style a few decades from now,
if that's what local government wants.  Yes, it's always better to have
the transit stop right inside the dense commercial core of a
neighborhood.  But if we make that an absolute requirement in our
thinking, we end up having to choose between either

1. underground lines in places where we can't afford undergrounding, or
2. elevated lines in places where community impacts just won't allow it or
3. lines at grade on arterial streets, even if in exclusive lanes,
   that can't deliver a reasonable travel time given the long regional
   trips the line is intended to serve. 

And on most of the American rapid transit projects that I've been close to over the last two decades, any of those outcomes would have killed the project.

The Overhead Wire takes up the topic in a post called "When Road Engineers Do LRT":

And one more post on transit routing from the blog Say Yes to the Honolulu Rail System, which is written by a communications consultant to the City of Honolulu on their proposed rail line. He objects to a new proposal that would not be fully elevated and -- it seems to me on first inspection -- would run closer to some downtown destinations by diverging from the freeway right-of-way. Anyone know more about the relative merits of these proposals?