I'm generally a supporter of urban development, and probably the most Lefty of all posters here, and *I* have some issues with New Urbanist thought concerning freeway removal. I understand the ideal of communities wanting to remove what they see as eyesores and blocks to local development, but I'm not so sure that pushing 60-80+K of traffic onto local surface streets will solve the issue, either.
My (possibly unfair) general impression of your posts is that you are somewhat to the right of me.
This said, in this thread I have noticed the advocates of I-345 removal have cited the CityMAP study almost as if it were scriptural authority. I have looked it up and I note that the I-345 removal scenario assumes (1) mode shift to transit, served by bus-only lanes, and (2) completion of the Trinity Parkway (when will
that ever begin construction?).
I appreciate that even with I-345 removed, there will still be alternatives for both downtown access and through trips. However, removing it breaks the downtown Dallas freeway box, withdraws network redundancy, and forces three-legs-for-one-leg routings for certain itineraries, such as approaching downtown from the south on I-45 and then using US 75 and US 82 to bypass I-35E north of downtown Dallas. And as Bobby5280 has pointed out upthread, Dallas is fast losing its uncongested informal 100% rural outer-outer bypasses. The rather flip suggestion of using I-635 as a north-south bypass of downtown Dallas ignores the 12-17 miles of added driving on a freeway whose congestion level is comparable to that of I-35E now that suburb-to-suburb commutes are dominant.
The CityMAP study in any case is fairly high-level. The study being called for in the RFQ will be more detailed and should take into account options for mitigating the operational issues and negative externalities associated with current I-345 (congestion, noise, visual obstruction, harborage of the irregularly housed, etc.) while retaining the viaduct configuration, as well as the practicalities of the trench and tunnel alternatives.
I wouldn't want to remove I-345 in expectation of a subway or other transit alternatives that might never materialize. I think a better way of managing the risk of possible collapse in transportation investment is to reconstruct I-345, eliminating to the extent possible the operational issues it currently has, and then look at retrofitting a subway and possibly imposing congestion pricing on I-345 once it is judged that subways are viable in the local travel market.