Screwston Denizen

This is being renovated as "Bell Heights," apparently a sort of colony for single thirtysomethings.

I think I will add that to my list. JJxvi's observation about the I-45 ramps being above trench level at that point is probably the reason for the lack of the Polk crossing, but I think the Polk bridge could be raised somewhat at the middle to potentially accommodate the ramps.

No need.

99% chance the profiles for this schematic were designed to criteria which means super-long sag curve lengths based on 60-70mph design speed. However, AASHTO sag curve calculations are based on headlight sight distance (HLSD). This whole thing is going to be under high mast lighting. Kyser and his minions back in the 70's understood this which is why the existing ramps bottom out quickly, and probably why the current schematic can't replicate all the braided ramp configurations that are out there now.

So: Design Exception for sag length on ramps and DCs, contingent on illumination. Set all your sag K values to 20-35, and BAM. Polk street overpass returns, all your local ramps come back, everyone's happy.

The Brits have a concept called "wide nodes, narrow roads." The idea being, build your intersections big enough to handle traffic loads, and then the individual corridors can be right-sized as needed. This is usually trotted out as an argument in favor of roundabouts, since it's easy to flare out a single-lane road to a double or even triple lane roundabout.

So let's talk for a minute about how adding more lanes is "already proven to not be a solution," a recurring argument alternately called "induced demand," "triple convergence," etc, and represented in this thread by Slick Vik. The way I see it, the Downtown Ring should be thought of as basically a single, really complex intersection. To that end, it should be big enough to handle all the traffic coming in to it. Individual corridors can still be congested, and we may choose to leave them that way due to the diminishing marginal returns of added capacity. But the main intersection shouldn't be the bottleneck.

 

Thoughts?

A lot of the backup on 610 is actually due to capacity constraints on the radial freeways just outside the Loop. You can see this on the 5:30pm Friday traffic image.

On the north side, you have a tight-radius ramp from the North Loop to 45 North, and then a mad scramble to the left as traffic from 610 tries to avoid getting sucked into the Crosstimbers and Airline offramps. That bottleneck jams the North Loop all the way back to 290, at which point the construction zone takes over. It also slows down the North Freeway into the Heights.

On the south side, both directions of 610 merge into 45 and then you lose a lane to the Park Place exit, so there's only four through lanes going past original Kelley's. That backs up the South Loop and 45 as far as Wayside. You have a similar situation on 288 south, where there's only three lanes going over Reed. That stacks up the South Loop as far west as Main/90A. On a bad day, the backup from 45 extends back as far as 288, and you experience the entirety of the South Loop as one continuous traffic jam. But 610 isn't the root cause, the radials are.

Howdy HAIFers. Longtime listener, first time caller.

I disagree that the combined 45-59 trench found in the latest proposal will render the Pierce unneccessary. Rather, I think there are so many additional managed lanes planned for Downtown that we will still need the Pierce - in addition to the combined trench - to convey it all.

http://purple.city/2015/04/30/making-things-worse/

Neither.