You know how pet gold fish only ever grow as big as the vessel that holds them will allow, some uncanny equation that always retains a natural proportion. Downtown, as a living organism, is very similar.
The highways around downtown Dallas create border vaccuums ringing the perimeter. Highways are about long distance connections. Downtowns are built upon millions of local connections: between it and adjacent neighborhoods, between offices and auxiliary/complementary uses, between residents and their work or their play, for workers to other offices, amongst friends, to restaurants, etc. etc.
We mistakenly think Downtown Dallas needs those highways to get people downtown. We have it backwards. The suburbs need those highways. They are a subsidy that tips the balance of choice in home buying towards cheap land and away from amenity. And you can be sure there is a tipping point in there.
Furthermore, as I said to a city councilperson the other night, a place can and should be judged on the quotient of people in a place above and beyond those that have to be there. Suburbanites coming into Dallas HAVE to be there. They work there. They bought tickets to a show or a game at American Airlines. They don't WANT to be there. Nobody WANTS to be near a highway.
Think of all of those connections like your fingers are locked together. Now have someone judo chop those hands apart. That is what highways do to local connections. Being antithetical to local connections, and incongruent to humane, people/pedestrian-friendly spaces/neighborhoods, they create borders, boundaries, if you will.
The little living, beating heart of downtown Dallas is the three block stretch of Main Street between Field and Ervay. Last night during Game 1 of the World Series, cheers resonated out of bars, restaurants, hotels, and residences up and down the street (along with groans later in the evening). It was real. It felt real, authentic. A real urban neighborhood.
Can it get bigger? Definitely, but we will see how much. Roads like Griffin, Elm, and Commerce create a cell within the cell as not quite highways, but effectively operating as such. They are the invisible hand preventing the gold fish from reaching the size of the entire tank.
Follow the lead of Milwaukee, San Francisco, and the many other cities planning to remove freeways like OKC, NOLA, Baltimore, etc. and create places that people WANT to be by tearing out the freeways.