Must increase the cost of the projects, surely. Immensely.
If you aren't familiar with the huge cost and the mega cost over-runs on the Boston underground highway called the BIG-DIG just do a search.
These kinds of projects are like a perpetual motion machine fueled by taxpayer dollars.
Labor Unions and contractors make financial contributions to politicians.
Politicians reward them with projects like this.
How often do we see crews making roadways wider to add more lanes on ground level highways?
What happens when these underground highways need to be widened?
What happens when these underground highways need to be widened?To expand Woodall Rogers, one would need to extend it under the frontage roads and then cantilever the frontage roads over the new construction. Re-doing the deck park probably wouldn't add 1% to the cost of a project like that.
But that wouldn't do much for congestion, as the expressways at either end of Woodall Rogers are already well above capacity at rush hour. Adding lanes isn't going to increase throughput.