Memorial Dr could get CID to pay for improvements (Atlanta: zoning, moving)
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What would the timing be for a Single Point Urban Interchange? https://en.wikipedia.org/wiki/Single...an_interchange
A SPUI could work in this area, if pedestrians are given enough time to cross. As it stands now with the 1/2 cloverleaf, drivers on the ramps are not looking for pedestrians, but instead merging traffic. I have almost been rear-ended because I stopped for a pedestrian crossing the EB ramp to NB Moreland.
With Spui, it is still a 3 way timing. The advantage is it removes conflicts caused by having two lights.
I don't know if I am good at describing this, but the advantage is typically when there is a heavier amount of cars getting on/off the freeway. The full diamond interchange is just as affective as a SPUI -if- the amount of time the turn lights need remain green doesn't need to be any longer than filling up the lane capacity on the bridge after/before a car turns.
SPUI's efficiency kicks in by letting you leave the turns lights green for longer periods of time. With a Diamond as traffic demands more turns on/off the interstates the 2 lights actually with up to a 7-way sequence as needed, which I didn't get into earlier. It gets confusing because the 4 additional sequences (when cars turn onto the freeway still allows for partial movement for cars going straight on Moreland, ie... a green light for cars going north on Moreland and turning onto I-20E at the same time is one of the additional 4) and they are not always all needed. With SPUI it is always 3. If they modeled this properly to test it (I can't easily tell if this is better or not), they will be concerned if too much of the traffic on/off the freeway is coming from just one direction (ie. if it is just heavier in/out of Atlanta the turn lights from the opposite direction might not need to remain green as long).
it would be a more expensive bridge widening project. The Intersection itself would be bigger.
If the problem here is mainly the freeflow and weaving caused by the two clovers and pedestrian safety just "straighten" up all the on/off ramps where it hits Moreland. Well not completely straight, but the turn radius doesn't have to be so big. It will have to remain wide so a semi could turn, though.
Particularly with the off ramp clover (I-20E to Moreland north) could become two right lanes and have a stop light. Cars can turn right as cars on Moreland South get a left turn light onto I-20 East and while the light allows cars and while cars from I-20E get a green light to turn onto Moreland North.
There would be a little bit of operational efficiency loss, though. The traffic numbers on the southern Cloverleaf, particularly in the afternoon, are bound to be heavier. During the light sequence, you'd have to add a moment where the light turns green going Moreland North (at the north light), so cars can continue to flow from the off ramp. Cars from the south going north on Moreland would have to wait for a green light a bit longer than presently.
The reason I like this is you can make Moreland Southbound green just as long. One key goal is to take cars away from Memorial/Moreland's intersection as quickly as possible, because of the proximity. The Memorial/Moreland intersection would remain the bottleneck that it is now, but not made worse.
Then for the existing shared right turn lane into the clover leafs, I would extend it just south of the southern traffic light. There wouldn't be anymore weaving from the two clovers and there would not be an empty lane cars can always yield onto.
For pedestrians this would stop the movements on the southern clover. For the Northern clover, no cars would be using it when the light sequence has the green light for the Southern Clover. This would still take due diligence on pedestrians to verify no cars are getting off the freeway only to get right back on going the opposite way, but that would be more rare and it would be easy for pedestrians to watch for.
It would also be possible on this same alignment to bring the onramp clover with a more perpendicular turn near the northern traffic light and make right turning cars stop when it is red when that I-20E cars turning onto Moreland South have a green light. It wouldn't slow traffic down, because in theory the Southern clover would have a green light at that time and no cars need to use that onramp.
This would still be an overall efficiency loss for car movements, but it is better than a diamond and keeps Moreland Southbound flowing longer.
One major point:
All of this needs to be put into the hands of the GDOT for a traffic engineering study and not an LCI study before anything happens. The LCI study doesn't do this, yet it recommends a pretty big change. The reason is they need to research traffic counts at each time of the day and computer model any changes. In the idea above, I'm making an assumption that flows are heavier to/from Atlanta and from Morelend on the north side and I'm making it a key goal to trying not to back up cars traveling south on Moreland. It needs to be tested at each time of the day too.
All of this needs to be put into the hands of the GDOT for a traffic engineering study and not an LCI study before anything happens. The LCI study doesn't do this, yet it recommends a pretty big change. The reason is they need to research traffic counts at each time of the day and computer model any changes. In the idea above, I'm making an assumption that flows are heavier to/from Atlanta and from Morelend on the north side and I'm making it a key goal to trying not to back up cars traveling south on Moreland. It needs to be tested at each time of the day too.
The neighborhoods have had enough of decades of GDOT ramming through projects based off traffic forecasts and little else. Commuters no longer get to trump residents.
This area was doing just fine before I-20 split it all apart. Today all the traffic counts peak the closer you get to I-20 in the area. It is a perfect example of how induced demand will just create more problems than you solve.
The neighborhoods have had enough of decades of GDOT ramming through projects based off traffic forecasts and little else. Commuters no longer get to trump residents.
This area was doing just fine before I-20 split it all apart. Today all the traffic counts peak the closer you get to I-20 in the area. It is a perfect example of how induced demand will just create more problems than you solve.
This is exactly a perfect example of anything other than short-sightedness on your part.
It seems rather important to actually model the changes appropriately, so we know what the effects -actually- are.
But "trump", "ramming"... geez give me a break. You sound like the tea party.
And for the record... most residents in that area are commuters and many of them are the commuters on Moreland using the interchange, so this is hardly such a white & black commuter vs. residents issue.
But seriously...
You didn't even live here when I-20 was made.
In 1950 Metro Atlanta had 726k people. The other 5 million of us would have had to go somewhere. Prior to the interstates' construction, many of the arterial roads were clogged up. Most people at the time loved the interstates traffic relief at the time, but there was a strong NIMBY sentiment in some areas that stopped a second wave of development in some areas. The reality is there were some pros and cons to what happened next and you're conveniently forgetting the pros.
Had the freeways not been made and somehow magically we still grew by 5,000,000 those neighborhoods would have -had to have been- completely rebuilt and we couldn't have many historic protection throughout the city in residential neighborhoods. Space would be far too valuable
All of the arterial roads would have to be bigger and probably more of them, even with the biggest utopian visions of simply relying on transit.
The zoning, housing, arterial roads, and most other infrastructure of this city never would have allowed for 5,000,000 additional people. Even now, with the freeways, it doesn't. That is why so many suburban areas have so many jobs and activity centers.
Of course the harsh reality is Atlanta probably wouldn't have grown so big and successful had we not built the interstates and other areas around us did.
So did the interstate help destroy or preserve all of these low-density intown neighborhoods? The quick answer is yes.
There are pros and cons of every decision in history you're refusing to acknowledge.
cwkimbro, the "more & wider" road crowd has had their day (60+ years really) and that philosophy has shown itself to be unsustainable. The real short-sightedness is trying to widen roads to fix traffic. It's like putting a band-aid on a gunshot wound.
I fully acknowledge that highways have helped suburbs grow, but that is not in a vacuum. Those freeways just funneled development away from cities to the suburbs. The city center still a fraction of the population it was before the freeways, a lack of "room" is not a problem here in Atlanta.
cwkimbro, the "more & wider" road crowd has had their day (60+ years really) and that philosophy has shown itself to be unsustainable. The real short-sightedness is trying to widen roads to fix traffic. It's like putting a band-aid on a gunshot wound.
I fully acknowledge that highways have helped suburbs grow, but that is not in a vacuum. Those freeways just funneled development away from cities to the suburbs. The city center still a fraction of the population it was before the freeways, a lack of "room" is not a problem here in Atlanta.
This isn't even a more and wider discussion. That is what is so short-sighted about this.
A lack of room for 5 million additional people + historical protections of low density 'urban' neighborhoods would have been an issue had freeways not been built in the first place.
A lack of room for 5 million additional people + historical protections of low density 'urban' neighborhoods would have been an issue had freeways not been built in the first place.
Yes, people's need for housing would have trumped "historical protection" of 30 year old single family homes. Even today most intown neighborhoods choose not to have "historical protection", including my neighborhood near this interchange. We don't want everything to stay unchanged, we just want the right sort of development. Not speedways widend through our neighborhood.
Anyway, is it me or are SPUIs not as popular as a potential replacement for busy freeway interchanges? Seems like the DDIs are now being talked up. With all the busy freeway exits we have I can't think of a SPUI in use except for PIB and Jimmy Carter. Well, and one on Sugarloaf Pkwy but that's far from busy.
Yes, people's need for housing would have trumped "historical protection" of 30 year old single family homes. Even today most intown neighborhoods choose not to have "historical protection", including my neighborhood near this interchange. We don't want everything to stay unchanged, we just want the right sort of development. Not speedways widend through our neighborhood.
Yes, I am aware of that. What is your point?
My point was, when I originally brought it up was you were doing the typical accusing freeways of being evil and destroying neighborhoods, yet they ironically have also created a model that lets them exist much closer to how they were originally built in the first place. Without them, they wouldn't be anything near what they are now. Without them, there is a high likeliness you wouldn't have moved here present-day. Atlanta would have never taken off this much and be this big.
Residents are stakeholder's in their neighborhoods, but the holier than though and the buck stops with them attitude isn't very productive either. There are tens of thousands of people in adjacent neighborhoods beyond this one area. There are millions in the region beyond that.
We all depend on some type of common system we must share. It is absolutely unrealistic to ignore that. That is why there are different types of roads with differences in mobility vs. access. That is why some roads are designated Arterial roads, some are federal/state routes, some are quiet city streets, some are collectors.
Anyway, is it me or are SPUIs not as popular as a potential replacement for busy freeway interchanges? Seems like the DDIs are now being talked up. With all the busy freeway exits we have I can't think of a SPUI in use except for PIB and Jimmy Carter. Well, and one on Sugarloaf Pkwy but that's far from busy.
Yea, I do that alot.
There are a few more SPUIs along Peacthree Industrial. They were popular when they constructed that stretch I guess.
SPUI is perfect for a road like Lenox at GA400. It's design can maximize the use of the on-off ramps by altering the traffic light timings. Lenox Rd on that northern stretch was really designed to be nothing more than a collector of traffic to and from GA400 and because of zoning and lack of residential road connectivity going north that northern part won't have too much demand for pedestrian traffic.
A DDI is perfect when there is a healthy mix of cars moving in all directions and is cheaper given that it fits on a narrower bridge. It makes it a 2-way light sequence, but the traffic that exits and moves straight is always mixed. So if there is ever a time when it is much more lop-sided to one or the other, it isn't the best design.
Another thing is we are trending towards using collector distributor systems more often these days it seems.
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