How much more traffic would use surrounding surface streets and freeways if 345 were removed? Those who want 345 torn down better not complain if they find surrounding roads much more congested than before.
If unsigned I-345 were removed it's a sure bet gridlock on surface streets would become a really serious problem in Deep Ellum and the junction between the N Central and Woodall Rodgers freeways. That is unless direct access to the neighborhood is removed by cutting off the thru roadways coming up from I-45 and down from N Central. That would solve any gridlock issues,
but it might be really bad for business in Deep Ellum too.It's also a sure bet that newly completed Horseshoe Project would get jammed up regardless of what's done about Deep Ellum surface street access to I-45 and N Central. The Horseshoe already funnels I-35E & I-30 traffic through downtown. Adding thru I-45/N Central traffic to that is going to put a serious strain on things.
LBJ Freeway isn't all that great an alternative to using I-45 and N Central to get through Dallas. Even with the completed expansion between I-35E and N Central it's still prone to monster traffic jams every bit as bad or even worse than jams that can occur in the downtown area. Routing I-45 along it is a non-starter.
Another alternative would be routing I-45 along the George W Bush Turnpike. But the GWB isn't going to be completed to the South side of Dallas for many years (if ever). The recent political moves to kill toll road projects threatens to grind any superhighway development to a halt.
Also, why should I care what residents in Sherman want? They don't live here. That I should be caring about what some people who live 65 miles north of me want so they can get to Houston 12 minutes faster once or twice a year is misguided.
I have plenty of friends and relatives who live in the Dallas area and none of them spend 100% of their time in their own local neighborhoods. They regularly have to drive to other parts of the metroplex or places out of town. Lots of people who work and play in Downtown Dallas live out in the suburbs and exhurbs of the DFW area. As rapidly as the DFW region is adding population the highway traffic capacity needs are only going to grow. It's already enough of a pain in the ass to get in and out of downtown Dallas. Removing that Southern-most 1.5 miles of N Central Expressway will increase the pain in the ass factor even worse.
I'll certainly agree the existing section of N Central between I-30 and Woodall Rodgers is an eyesore and works to divide downtown and Deep Ellum. I think the best solution, but also most costly, is to replace the elevated freeway with a cut & cover tunnel similar to building Klyde Warren Park over 3 blocks of the Woodall Rodgers Freeway.
San Francisco tore down the Embarcadero Freeway and turned the area into a park, the world didn't end. New York City's economy and infrastructure didn't collapse when they tore down the West Side Highway and turned it into a surface street.
Comparing the West Side Highway/West Street in NYC and the Embarcadero to the first 1.5 miles of North Central Expressway is an apples to oranges comparison. The West Side Highway and Embarcadero were not along major thru traffic corridors. When those two freeways were removed/stubbed their host cities were already pedestrian friendly and had well developed subway and bus systems. The DFW metro is still very much a vehicle-centric region. The Dallas light rail system and regional passenger rail networks aren't yet developed enough to provide an effective alternative to car travel for everyone in that region.