The miles of highways defining Collin County—including Highway 121—originally made for commuter cities. But as the county's powerhouse cities of Plano, McKinney, Frisco and Allen come into their own apart from their identity as suburbs of Dallas, they've got a few kinks to work out. We sat down with Cencor Realty Services EVP David Palmer, Hines managing director Drew Steffen and Granite Properties development director David Cunningham to hear their thoughts. Hear more from the Davids and Drew—and many others—at our 121 Corridor Expansion event Aug. 25.

The four biggest cities in Collin County—Plano, Frisco, McKinney and Allen—have seen 6% to 8% year-over-year growth. Last spring, the Dallas Observer famously reported that Collin County might be bigger than Dallas in the next 35 years. With that kind of growth, you'd expect growing pains to be especially—well, painful. The area has managed to thrive under the added demands of a growing population, but there are pressure points.

First, developers find that many don't have a clear understanding of the area. Perceptions haven't quite caught up with reality—many people would say that if you're not developing around Frisco Square or Legacy West or Watters Creek, you're nowhere, Drew tells us. Drew finds himself having to explain the necessity of other projects in proximity to 121, but also sees that it is within the inevitable path of growth, it's only a matter of time before the cities build out.

David Palmer (above, pointing to map) sees a similar disconnect with the realization of residents' spending power. From the northeast end to the southwest end of 121, there's a lot of dollars waiting to be spent. Palmer says the perception of the west end of 121 having lighter spending power is empirically untrue in Cencor and Weitzman's experience.

But all can agree on the future issue of traffic. How the area handles the need for better roads, more schools and more healthcare options is the biggest question today, Parker tells us. With tons of corporate relocations creating jobs, and thousands of forthcoming multifamily units and buzzworthy retail and restaurants (Dean & Deluca, Hash House A Go Go and Hurts Donuts, to name a few), traffic isn't getting any better.

And public transit may not really help. Some—including David Cunningham (right, at a past Bisnow event)—think that Collin County is, by definition, a driving city. He thinks mass transit won't ever happen because all the tollways (Dallas North, Sam Rayburn and George Bush) won't want to compete. "Long term, that's the Achilles heel of this area," Cunningham says.

Drew says many play to the hope that residents will stop desiring to commute back and forth to Dallas, therefore eliminating the need for public transit. "We want to be a destination within ourselves," he says.

And with the seemingly endless live/work/play options, residents could theoretically exist unattached to Dallas. But first these cities must fine-tune their own identities. They're still evolving and have room to define their personalities, especially amongst themselves.

Hear more from David, David and Drew (and lots of other guys whose names start with the letter D) at our 121 Corridor Expansion event on Aug. 25. Register here.