Synchronized Traffic Lights

Is it just me, or is the traffic jam at the Highway 74 and Highway 54 intersection in Peachtree City just about as bad as it has ever been - in spite of all of the investment in additional traffic lanes and new "synchronized" traffic signals?

1. Traveling eastbound on Highway 54 and trying to turn onto northbound Highway 74 it seems the left turn arrows never stay green long enough to allow the left turn lanes to clear. Sometimes I wait two (sometimes three) cycles of the turn arrows to make a left turn.

2. Traveling westbound on Highway 74, there are times that traffic still backs up almost as far back as the Peachtree City Library.

3. Vehicles turning west onto Highway 54 from Highway 74 northbound still often block southbound traffic on Highway 74 because of the backup on westbound 54 from the trafic signals at The Avenue.

4. And I have to say that I don't think traffic entering Highway 54 eastbound from the drive between the Starbucks and Eckerds Pharmacy at The Avenue should be allowed to cross all the eastbound lanes of Highway 54 to enter into the northbound turn lanes for Highway 74. What a mess that creates!

I grew up in a city that had "synchronized" traffic lights. For me, that meant if I drove at the speed limit, I was mostly guaranteed to have a flow of green traffic signals all the way through town. So, it begs of the question, exactly what IS "synchronized" on the Highway 54 corridor? After all the investment in expensive traffic signal controls that were supposed to communicate with one another to improve the flow of traffic it seems as bad as ever! Does anyone know what the Georgia DOT means when they use the word "synchronized"?

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bad_ptc's picture
Submitted by bad_ptc on Sun, 03/01/2009 - 10:33am.

Contrary to popular belief on the part of three council members, the process of “Synchronizing” a collection of traffic lights is a tremendously difficult and costly thing to do.

Without having sensors or some other means of determining the current traffic pattern/volume along a given stretch of road-way in combination with all of the ancillary/feeder roads there is NO way to “synchronize” anything.

Basically the traffic light system has no way of knowing if there are three or three hundred vehicles waiting to go.

PTC OK's new 54W light on 3-2 vote

“Several conditions were attached to the approval, including a requirement that the developer have the traffic lights in the corridor resynchronized, and the installation of a "loop" for traffic coming off Planterra Way and turning right onto Ga. Highway 54.”

The condition, “developer have the traffic lights in the corridor resynchronized”, was made by councilwoman Plunkett.

I openly challenge Mrs. Plunkett to tell us that she has any idea what it means or what it will cost.

Below is a brief explanation of ‘synchronization’ from the Smithsonian/NASA Astrophysics Data System.

Synchronized flow and wide moving jams from balanced vehicular traffic

Siebel, Florian; Mauser, Wolfram

Physical Review E, vol. 73, Issue 6, id. 066108

Recently we proposed an extension to the traffic model of Aw, Rascle, and Greenberg. The extended traffic model can be written as a hyperbolic system of balance laws and numerically reproduces the reverse- ? shape of the fundamental diagram of traffic flow. In the current work we analyze the steady-state solutions of the model and their stability properties. In addition to the equilibrium flow curve the trivial steady-state solutions form two additional branches in the flow-density diagram. We show that the characteristic structure excludes parts of these branches, resulting in the reverse- ? shape of the flow-density relation. The upper branch is metastable against the formation of synchronized flow for intermediate densities and unstable for high densities, whereas the lower branch is unstable for intermediate densities and metastable for high densities. Moreover, the model can reproduce the typical speed of the downstream front of wide moving jams. It further reproduces a constant outflow from wide moving jams, which is far below the maximum free flow. Applying the model to simulate traffic flow at a bottleneck we observe a general pattern with wide moving jams traveling through the bottleneck.

DOI: 10.1103/PhysRevE.73.066108

City of Santa Clarita Traffic Signal Synchronization

Traffic signal synchronization is a method of timing groups of traffic signals along an arterial to provide for the smooth movement of traffic with minimal stops. The quality of the resulting progression is a function of the spacing of the signals, the prevailing speed, the amount of traffic coming in and out of driveways between traffic signals, the uniformity of intersection sizes, and the cycle length. The traffic volume and the proportion of the green time given to the preferred movements are also important.

Advanced Transportation Management System Elemental Cost Benefit Assessment
Authors: Perrin, Joseph, Rodrigo Disegni, and Bhargava Rama

Summary Information

The Utah CommuterLink Advanced Transportation Management System (ATMS) was developed so that operators in the Utah DOT Traffic Operations Center (TOC) could monitor and manage freeway and arterial traffic flow in the Salt Lake Valley. The ATMS consists of numerous components: a signal system, incident management team (IMT), variable message signs (VMS), ramp metering stations, highway advisory radio (HAR) system, closed-circuit television (CCTV) cameras, traffic monitoring stations (TMS), and road weather information systems (RWIS). The TOC is connected to a Salt Lake City and Salt Lake County traffic control center. The field devices and centers are connected via a fiber optic network which was installed as part of the ATMS deployment.

System Cost
Capital cost: $106 million
Annual maintenance cost: $377,800
Annual operational cost: $2.3 million

Submitted by Spyglass on Sun, 03/01/2009 - 5:57pm.

before or after the fact (the vote)?

bad_ptc's picture
Submitted by bad_ptc on Sun, 03/01/2009 - 6:38pm.

This is something that’s been taught in middle school math and high school calculus and physics classes for decades. Don't you remember the old, "If train A leaves the satiation heading west at 20 mph" word problem?

If I’m not mistaken each member of the council must take and pass several university courses on urban planning which includes among other things ‘traffic management’ and budgeting.

Besides, doesn’t the city pay for an engineer and an entire planning department staff?

The thought of me trying to explain something akin to fluid dynamics to those three is enough to make me sick.

FYI, this is the same principle behind how the internet works; something my 13 year old studied in middle school last year.

Submitted by Spyglass on Mon, 03/02/2009 - 11:16am.

And until we fix the bottleneck going to and from Coweta/Fayette, we will continue to have trouble at this intersection. It's not nearly as bad as many areas of Metro ATL, but it could be better. We MUST have more access from Coweta/Fayette. Until we get it, folks will continue to bitch and moan about traffic at limited times at this intersection in question.

bad_ptc's picture
Submitted by bad_ptc on Mon, 03/02/2009 - 8:45pm.

“It's not nearly as bad as many areas of Metro ATL, but it could be better.”

Mass Transit Grows as Commuters’ Trip of Choice
NYT, Published: September 2, 2006

“Washington and the surrounding suburbs in Maryland and Virginia rival New York for long commutes, with a few counties in that region showing average trips to work taking more than 40 minutes. But, if the census figures are to be believed, there is one place in America that is the capital of hard-core commuting: Coweta County in Georgia.”

“Residents of Coweta County, a fast-developing slice of suburbia south of Atlanta, spent an average of more than 51 minutes getting to work last year, almost 10 minutes longer than the typical commute in any other county in the country, according to the survey results released this week.”

Please remember Coweta County has three, count-um, three interstate interchanges. Fayette County has NONE.

"We MUST have more access from Coweta/Fayette."

You are 110% correct; we do need additional east/west access between Coweta and Fayette but NOT through the middle of PTC.

To you statement, I wrote this back on Nov. 2006.

“How about widening GA 85 from 16? How about building a road say from the 74/Senioa Rd to Fisher or I-85. The cows might not like it but it will have far less impact on the people.”

The only problem with doing what I suggested is that the Hwy. 74 interchange doesn’t belong to Fayette County. That interchange isn’t slated to be ‘improved’ for another ten years as per the GADoT. By that time Fulton County will have planted all the furrows of town houses and cross-dock facilities the ground can hold.

The land along Hwy. 74 on both sides of I-85 has seen and will continue to see massive apartment and townhouse development as time goes by.

I had the great pleasure of having to go on Oakly Industrial Blvd. just this afternoon and couldn’t help but notice the rows upon rows of townhouses. They reminded me of a farmer’s field because of how neat the rows were planted. There must be thousands of townhouses and apartments back there along with a never ending stream of 18-wheelers.

Don Haddix's picture
Submitted by Don Haddix on Mon, 03/02/2009 - 10:21am.

Yes, we have courses we take that are very important to running the city. Takes two to three years to complete the recommended levels. One is mandatory by State Law.

Problem this year is our funding was heavily cut. The majority already completed theirs while Sturbaum and I only have one year's worth completed.

With probable new Members coming on next year that funding will have to be restored. No option.

Yes, we have an engineering and planning Dept. But, in specialty areas such as relates to GDOT, specialists are brought in.

Problem there is PTC allows the developer to pick and hire the specialists, as happened here on this traffic and light issues.

Sturbuam and I both brought up the issue, when first on Council, that PTC should be hiring all the specialists to do the traffic, economic and environmental impact studies, at developer cost. Not the developers. We went unheeded.

The impact studies are required by the Comprehensive Plan. Common sense tells you the specialists are going to be hired to, and will, represent the client, not PTC. And that they should be complete studies by current standards.

Syncing these lights will not fix 54. I believe you were there and heard all my challenges, including the scope of the area being looked at being far too limited, how the lights would have to sequence to provide turn opportunities from such as Planterra Way onto 54, impacts all the way back to Wyndham during periods of the day, causing more delays on connecting roads, including 74 and so on.

Sturbaum also challenged the vehicle spacing used as not the norm for GDOT and using the true spacing numbers would greatly increase delay times.

This is indeed flow dynamics and adding that light supposedly only adding about 12 seconds delay is astounding to me. Anyone able to create and read a flow chart can see what is going on here.

Flows change over time, so, as you said, syncing would have to be repeated and/or maintained over time.

Even the simplest way, as purposed, is about $45,000 a time. That gets expensive.

Bottom line here was the goal. The goal was to allow the SUP development, not making 54 better.

Don Haddix
PTC Councilman
Post 1

Submitted by Spyglass on Mon, 03/02/2009 - 11:19am.

lack of access from Coweta/Fayette. How far south and north is it to the next access points? 4+ or so miles in either direction is a good educated guess. A good majority of autos trying to get West on 54 in the evening are Coweta tags. It's not their fault that the two counties can't work together for better access. I've seen the same thing happen at Cobb/Fulton around the River.

Until we address it, we will continue to have problems at times.

Don Haddix's picture
Submitted by Don Haddix on Mon, 03/02/2009 - 12:34pm.

I backed the addition of a north/south in Coweta, with spaced connector roads, around 15 years ago, I believe it was, because it was obvious too much traffic was having to use 74 for both Fayette and Coweta. Also obvious it was a problem that would do nothing but grow, which it has. That got shot down by people in both Fayette and Coweta.

That would have had a major impact on how traffic and other issues would have developed over time. Instead of everything coming our way I think it would have kept more of it over there.

Problem with TDK was that it would add to the problems, not reduce them, for PTC.

Did you see ALL the housing plans Coweta had signed off on that would have dumped north bound traffic right onto 74 from TDK? I have and I am not talking just the McIntosh Village, but a whole series of housing developments with roadways that would have fed to TDK.

We would have been buried in cars. There would then have been two major accesses feeding traffic north on 74 instead of one.

The widening in Coweta of Fishers will help. It needs to extend south to 85.

We need some serious traffic studies to see how to add by-passes to the 74/54 intersection. Just funneling more traffic into PTC via TDK or any other current road will not help. We need a way to get it around PTC for both north and south bound traffic.

Straight through traffic on 54 isn't going to change for those immediately off of 54. TDK would have had no impact on that trafic. We have to bleed off the traffic that has no other way of heading north or south but to use 74.

The problem is now a regional one, meaning a radius of X miles from 54/74 and what alternatives can be created. Adding a second traffic region from Fishers Crossing will be a plus.

No easy answers on this big problem.

You are correct on the lack of cooperation between Coweta and PTC on these issues. Being right on the Coweta County line is not a plus for us. Coweta has more of a Gwinett or Cobb mindset on development and vision. So they are more than willing to build a mini city full of their standards right against our border, which is not good for us.

Don Haddix
PTC Councilman
Post 1

Submitted by Full Time Observer on Mon, 03/02/2009 - 1:17pm.

Yes, there are probably a lot of things that could have been or should have been done in the past. There are probably lots of things that probably can be done or should be done in the future. But is there anything that can be done right now to improve the traffic flow in the Highway 74 and Highway 54 corridors?

Don Haddix's picture
Submitted by Don Haddix on Mon, 03/02/2009 - 1:35pm.

The soonest possible, I think, would be GDOT rejecting the traffic light application. That is a possible outcome of all of this. That would not be an improvement, but stopping a deterioration.

The next would be the completion of McDuff, whenever that will actually be, which will provide a by-pass to and from 74 North. That will give some significant relief on 74 and 54. but I can hear the complaints from Centennial and that area already.

After that would be completion of the widening of Fischers Road, which should bleed a fair amount of traffic north bound to 85 from 74.

Distant future would be the split grade intersection of 74/54. That will eliminate the stop time of the through light for 74 and help on 54.

Unless I am forgetting something, that is about it.

Not real inspiring, I know.

Don Haddix
PTC Councilman
Post 1

Submitted by Full Time Observer on Tue, 03/03/2009 - 6:37pm.

I wanted to follow up on the idea of starting with just one accomplishment - the importance of getting one thing done. Then one more after that, and so on. Since The Avenue is private property and its streets are presumably not controlled by the GDOT, is it possible the PTC traffic department could erect a sign at the exit onto eastbound Highway 54 between the Starbucks and the Eckerds Pharmacy that said: RIGHT TURN ONLY. NO ENTRANCE TO LEFT TURN LANES. That would eliminate a bottleneck.

Pleased to see the PTCPD intend to start enforcing intersection blocking. That happens frequently along Highway 54 from Robinson Road to Westpark where cars making left turns pull half way across Highway 54 and stop - blocking the vehicular travel lanes. It is worst at Petrol Point, the McDonalds, and at Westpark.

Don Haddix's picture
Submitted by Don Haddix on Tue, 03/03/2009 - 10:06pm.

No, PTC PD cannot do that.

The driveways, meaning what connects the private property to 54, are on GDOT right of way. GDOT has to approve all driveways, which they already did in this case.

Once the traffic hits the driveway it is GDOT who sets the rules.

A request would have to be sent to GDOT. That requires it meets their warrants to be granted. Part of such a warrant procedure is the number of accidents, normally.

We have had some go rounds on certain areas that need something but gets refused because the accident warrant isn't met, yet.

Don Haddix
PTC Councilman
Post 1

Submitted by Full Time Observer on Wed, 03/04/2009 - 12:48pm.

Perhaps we've reached a point where there's so much government, so much regulation, and so much bureaucracy that it impedes simple, easy, common sense things that need to be done? Do you have any idea when the GDOT is going to install the traffic signal at Highway 74 and Wisdom Road? I have to believe it's been more than a year since that project was approved and there's been nothing but poles lying in the grass for several months.

Don Haddix's picture
Submitted by Don Haddix on Wed, 03/04/2009 - 2:45pm.

Is a struggle to find many times. It bogs things down way to much way too often.

Really gets old trying to get something down when you get told months, or years, before you will get an answer to a permit, etc, from State or Federal.

As for the current status of the traffic light, and some other issues, it is in the Retreat packet found here.

You may want to saved it to desk top since that link will not be there for long after the Retreat.

Firm dates on lights and other road projects are anything but firm anymore in this economy.

Don Haddix
PTC Councilman
Post 1

Submitted by Spyglass on Mon, 03/02/2009 - 1:29pm.

You can only get so many cars through. I'm not advocating TDK, or any one road. But we need more ways to get to Coweta and they need more ways to get here.

Don Haddix's picture
Submitted by Don Haddix on Mon, 03/02/2009 - 3:10pm.

For what purposes does anyone need more ways to get here? Or us to go to Newnan? 54 is the most direct route.

Coweta to east of PTC bound pass traffic, or the reverse isn't going to change on 54.

Most assuredly, though, if Fischers went from GA 85 to US 85 that would bleed off a lot of traffic. It would no longer need to come through PTC at all.

A by-pass between 74 and 54 would also bleed of a ton of traffic for those with other destinations than PTC that must use these two roads.

Yes, there are workers going both directions, but you have to be extremely careful on what roads you add because adding the wrong road in the wrong place encourages the incompatible planning and growth goals of Coweta that is hurting our traffic situation in PTC now.

Coweta has demonstrated they have no problem in building things across the line for which they perceive they will get the benefits and we will get the costs.

So, I don't know what all this traffic is that needs additional access to PTC and Newnan. Please explain.

If you are going to say for shopping, that doesn't fly because Wilksmoor, with all that heavy traffic, has one of the highest vacancy rates, even if you look only at sq', which is currently 8.45% for that area. Probably up to about 25% by store front.

Don Haddix
PTC Councilman
Post 1

Submitted by Spyglass on Mon, 03/02/2009 - 9:18pm.

I'm sure much more needs to be said. We have a 2 land road (hwy 54) over the RR tracks in each direction, same at Line Creek. The McDuff road would help, but I think more access is needed. It doesn't help that Walmart sits right at the choke point, and it is utilized by Fayette and Coweta shoppers, probably about equally.

Both Coweta and Fayette will continue to grow into the future. Fact is, Hwy 54 as it is currently constructed, doesn't have the capacity to properly serve without tieups at certain times.

As to your shopping/vacancy question, and the square footage comment, welcome to the real world. That is the ONLY way to compute occupancy/vacancy rates.

Don Haddix's picture
Submitted by Don Haddix on Mon, 03/02/2009 - 10:34pm.

Total sq' is not the only way to evaluate such. That is the Old Growth way of looking at things. Smart Growth is more complex and proving far more successful in application.

My family didn't move here to go the way of Gwinett, Cobb, Newnan or Riverdale as concerns growth. They are incompatible with the Village Concept.

So, obviously, we are not going to agree on how to proceed.

Don Haddix
PTC Councilman
Post 1

Submitted by Spyglass on Tue, 03/03/2009 - 2:12pm.

This is getting good. How does the City go about collecting on Business/Occupational Licenses? Do they go by employees? Square Footage or the number of Front Doors?

How about setting City Taxes? Does the County set a value by the square footage and value of the building? Or do they just how many DOORS do they have?

You seem to think that I'm for a free for all. You couldn't be more wrong.

Don Haddix's picture
Submitted by Don Haddix on Tue, 03/03/2009 - 2:53pm.

License are a mix of issues, such as footage and employees.

Permits are based on sq', usage and codes.

Business property tax varies. For 20 years I paid it by a combination of sq', inventory and more.

Homes are based on sq' plus land and amenity value.

No evaluation of anything is based on just sq'.

There is a big difference between the impacts of retail boxes and retail Big Boxes in general. Normal retail is local with a higher effective net income tax impact on a city than is Big Box, which is regional in impact.

Even the National Retailers admit there should be about 10.X sq' per consumer. The US averages double that and is about the highest in the world on numbers. Canada, in example, is about 10.2 per consumer.

So, as with the rest, it isn't an issue of just sq'. And current numbers show we are extremely above that 10 number already.

Don Haddix
PTC Councilman
Post 1

Git Real's picture
Submitted by Git Real on Sun, 03/01/2009 - 1:54pm.

You need to run buddy. I've got few hundred for ya to start the kitty.


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