Chris Leinberger, urban developer and Brookings Institution wonk, is the latest guy with a suitcase (the latest expert, in other words) to visit Raleigh and tell us to get with it transit-wise or else be left in the 21 Century-Knowledge Economy dust. He added one new note not heard so clearly before, at least in my recollection: Rail transit, yes; bus transit, no, because nobody will ride a bus in America unless they have no other choice. “I’ve never seen a dollar of real estate investment generated by a bus stop,” he added.

I blogged the other day about Leinberger’s formulation for “walkable urban” places (the antithesis of our vastly overbuilt “drivable suburban” developments) and how many a metro-area can expect to have. The Triangle region is expected to have a population of about 1.7 million in 20 years, he noted; based on his calculation that 1 million people should generate 4-6 such places — but no more — he said we should be thinking of the 10-11 places we’d like to see be “walkable urban” in the region.

Right now, he said, only Downtown Raleigh, from what he saw on a daylong tour with Raleigh Planning Director Mitch Silver, even potentially fits that description, and it still has a long way to go to fulfill it. Downtown Durham is stirring, he added. Otherwise, we’re nowhere, walkable-urbanwise.

I asked Leinberger, since Raleigh’s population is almost 400,000 and projected to be about 600,000 in 20 years, whether we in Raleigh should reasonably anticipate having 4-6 such places within the city? (I was being generous with my math.) But we’re looking, I added, at a comprehensive plan — draft version — that designates at least 8 “growth opportunity” zones, and maybe more depending on how you read it, some of which are on the proposed rail-transit corridor, some on highways. Have you ever seen a “walkable urban” place on a highway? I asked.

He laughed.

And if we designate too many places for urban densities in our plan, I went on, are we not running the risk of undermining the prospects for the 2-3 rail-station locations (in addition to the one in Downtown Raleigh) that we’d really like to see become “walkable urban” places — and that actually have a chance of becoming same?

I don’t think Leinberger ever answered that question. Mitch Silver first wanted to “clarify” that, if by highway locations I was talking about Crabtree Valley and Brier Creek, they are potential stops on a future light-rail route down Glenwood Avenue that won’t be built in the next 20 years, perhaps, but could materialize some day. I think Silver also mentioned a Wake Med-New Bern Avenue location off I-440. (I don’t have a recording of what everybody said, but the session will be televised by the City of Raleigh’s Public Access TV system.)

I don’t put the New Bern Avenue site in the same category as the first two, but yes, I was thinking of Crabtree and Brier Creek and also of North Hills and Triangle Town Center, “places” on I-440 and 540 that will never, in my mind, be walkable or urban or even walkable suburban. Not unless you tear them down and start over.

Leinberger did answer, if I heard him right, by underscoring his point that rail stations shape development by attracting upscale users and the real estate investors who love them, whereas bus stops– in part because bus routes are flexible and impermanent — don’t.

His study of metro Washington, metro Atlanta and others, he said, shows that “walkable urban” communities come in five forms: (1) downtowns; (2) downtown adjacents; (3) new town centers in suburban places; (4) old suburban malls torn down and replaced by faux town centers; and (5) “lifestyle centers” built in greenfield locations and made to look like old-timey downtowns.

What the five types have in common is a street grid pattern, he said, and fine-grained planning and design to make high(er)-density development fit comfortably on the grid, so that it’s approachable by transit, car, bicycle or on foot. But once you’re there, you’re there, and you can walk comfortably without dodging the traffic. That’s why people like being there, and living there.

Of course, achieving that mix of density and walkable space, and cars and people, ain’t easy. Piece of cake to stick a big building on a cornfield somewhere, Leinberger said. “Walkable urban places are far more complex” to build and manage.

And 90 percent of the “walkable urbans” that Leinberger’s found out there, whether in downtown or suburban locations, are located at rail-station stops. That allows the people who live there to get by with one car in a two-adult family or perhaps even no car — and every car you don’t own and drive 15,000 miles a year is $7,200 a year of after-tax savings, so figure an additional $10-15,000 in income.

“Rail,” of course, can mean streetcars powered by overhead electric lines as well as big ol’ transit trains. The point is, they run on tracks, and the tracks go from one “walkable urban” place you like (and maybe live) to the other “walkable urban places” you also like.

So in 20 years, where are the 2-3 “walkable urban” locations in Raleigh that we hope to see come to fruition on rail-station stops connected to the one downtown locations that’s already coming together sort of?

And how are we doing to make that happen? To me, that’s the number one question the comprehensive plan should answer. If it doesn’t, all the other answers it tries to give can’t possibly be right.