Traffic Misconceptions
Thursday, March 10, 2011 at 10:57PM 
I was reading a local blog recently and came across a tongue in cheek post about traffic in Alpharetta. The premise was that Alpharetta is doing all these nasty things that will actually make traffic worse. There were a number of misconceptions in the post and it concerned me that there might be some confusion on these points down here in Roswell as well.
As a member of the Roswell Historic Gateway Community Advisory Group, I am aware of the challenges of balancing traffic capacity needs with livability and aesthetic needs. So, I decided to compile a number of common traffic misconceptions together and elaborate on them for the benefit of my readers.
Many assumptions that would seem to be logical at first glance actually end up being mostly incorrect when put to the test. One of the biggest is the assumption that density brings traffic. Residential or commercial density with no where to go and nothing to do creates traffic as everyone has to leave their home by car to do even the most mundane of tasks. That's just one misconception of many that we will address below.
Making Roads Narrower Creates Congestion - The conventional wisdom is that narrower roads bad for traffic like narrower arteries are bad for your heart. This is moderately true. First, let's look at a little info on lane widths. The authority on highway and road designs, the AASHTO Green Book, recommends that local roads be between 9' and 12' in width, collectors be between 10' and 12' and that arterials be between 10' and 12' with 11' being the minimum in rural areas.
Now, those are some really wide lanes if we decided to go to 12' in all areas. That would mean that a four laner with no shoulder and no median would be over 48' in width. That's quite a bit of real estate. Now, let's say we narrow that down a bit to 10' and think about what it will do to the flow of traffic. Well, not much according to several studies. The worst of which shows a 6.66% decrease in flow while the best shows no meaningful change.
Narrowing lanes also makes the driver more vigilant and in turn causes the driver to drive more slowly which flies in the face of the next myth.
Narrow Lanes Cause More Accidents - Believe it or not, this isn't actually true in all cases. Studies show that narrowing a lane from 12 feet to 10 feet has no noticeable impact on the number of accidents that occur on the street. So, the concern of increasing crashes when lanes are narrowed is not actually a concern at all. However, if you take lane widths down below 10 feet on a non-residential road, you will likely experience an increase in collisions.
The historic district currently has narrow lanes in many areas and they work just fine for both capacity and safety. They also work pretty well contextually helping to create a sense of place. We have character and capacity with relatively narrow lanes. What we really need to do is kill the reversible lanes (which is a stated objective of the historic gateway project).
Mixing Pedestrians with Cars Creates Congestion - Putting pedestrians ON the road with cars would definitely wreak havok on traffic and local ERs. The assumption is that making roads pedestrian accessible increases traffic. Mixing pedestrians with cars doesn't impact traffic either way unless there are other factors at play. However, if properly designed, a highly walkable environment encourages people to get out of their cars and walk. There is less of a reason for cars to be present. Thus, we could make the assumption that there would be fewer drivers. Generally, if there is high pedestrian traffic and high automobile congestion, it is because the location is a desirable location. It is not because the pedestrians are there. Building a road that accommodates pedestrians will not in itself create traffic. However, if you build a place that people want to be, you might see some traffic.
Roswell already has one area where pedestrians are very active. That is Canton Street near the Atlanta Street/Alpharetta Hwy intersection. The traffic there isn't due to the pedestrians, sidewalks, crosswalks or narrow road widths. The traffic there is due to the demand of the location. If we wanted to widen the lanes and add more lanes and take away the sidewalks, we'd be losing something very special that many other cities envy. Build places that people want to be and you're going to get some traffic.
High Density Development Creates Traffic - This one is legitimate under the assumption that you pack people into condos and create a dense SINGLE USE environment. Single use environments are a sure fire way to create traffic. Mixed use development can induce traffic as well but it doesn't have to. It really depends on whether the street network is set up to provide multiple routes and whether there are enough destinations within the mixed use area to encourage people to walk significantly more than they would in a less dense environment. Perimeter Center is a bad example. Atlantic station is an excellent example. This study by the the Transportation Research Board concludes that a doubling of residential density coupled with an increase in nearby employment, transit and mixed use can decrease vehicle miles traveled by 25%.
No one is calling for Atlantic Station in Historic Roswell. However, working on gridding the street network to provide more connectivity and driving, biking, walking options should be a strong focus of any redevelopment that occurs in the area.
Lowering the Speed Limit Creates Congestion - This one actually is true.. but not as much as you might think. The reduction from 45 mph to 35 mph is only about 3% of capacity. To go from 45 to 30, you're going to cut capacity by slightly more than 5%. So, you're really looking at trading capacity for safety. A collision at 30mph is significantly less damaging (especially to a pedestrian) than one at 45 mph. I've included a telling chart on pedestrian death by speed.
If we want a safe environment for everyone, we should design the street from the river to the square for 30mph and enforce a 30mph limit on that stretch. It's 1 mile of road and 30mph isn't going to kill any commute. You go slower than that on 400 sometimes.
So, what are real solutions to traffic?
First, remember that traffic isn't necessarily a bad thing. Most of the time, it means that you are somewhere that people want to be. However, Americans collectively spent almost 500,000 years stuck in traffic in 2007. That is more than double the 14 hours the average person spent in traffic in 1982. This was not because America was narrowing roads, building bike lanes and walking more. It was actually because we were spreading out, widening roads and trying to run every errand in our car. Food for thought when thinking about how we want to move forward. Below are some of the best tools out there for traffic mitigation. There are too many small tools to list so I'm sticking to the big ones.
Zone for Mixed Use Development - The objective here is to reduce the nubmer of trips that residents, workers and visitors need to make while allowing the flexibility to drive if needed. Atlantic Station is a phenomenal example of MU development. A study of AS residents showed that after moving into the neighborhood, residents experienced a remarkable 73.5% reduction in daily vehicle miles traveled. If you have visited AS, you would notice that there is a quality public realm that encourages walking and pedestrians and cyclists are able to safely cross roads and cars can still freely move though the networked street pattern.
We need both vertical and horizontal mixed use in the historic district. This will create the interesting and walkable environment that the vast majority of the residents here are looking for. When I say vertical, I'm thinking of a maximum of 4 stories with retail or office on the ground floor.
Network your Streets - Connectivity is a key to reducing traffic congestion. The problem with the suburban land development pattern and the amount of traffic we experience is that in far too many cases, there is only one reasonable way to get from point A to point B. In an environment where the road is networked, there are many different routes to get to the same destination.
As previously mentioned, we need a better more connected network
Find Reasons for People to Use Their Cars Less - This could be any number of things not the least of which is $3.60 gas. Create meaningful neighborhoods. If more neighborhoods had shopping, jobs, parks and entertainment closer to the actual residents, those residents would drive less. This takes us back to the Atlantic Station example above.
You'll notice that I don't have transit on this list. A large misconception about transit is that it should relieve congestion. It actually has very little to do with congestion. Rather, it creates modal diversity and offers redundancy and flexibility within the system. It also allows the underserved 30% of the population that can't or shouldn't drive to function in society without being a drain or a risk.
I hope I've made some sense here and I'll be happy to provide studies that affirm the statement above upon request. Additionally, if you are ever curious about the hidden causes of traffic, please pick up the book Traffic by Tom Vanderbilt. It should be required reading for new drivers. His blog is www.howwedrive.com and is very interesting.
images: HelloAtlanta.com, SafeRoutesInfo.org, CNU
roads, traffic, walkability in Misconceptions, Sprawl, Transportation
Reader Comments (6)
I'm glad I could provide you with some good blog fodder! Figured that might happen. I appreciate your reply, yet I think you made as many of my points as you argued with.
For what it's worth, I didn't mention accidents in my article. The lane narrowing and pedestrian projects I referred to where along highway 9 in Alpharetta connecting into Milton. Unlike Roswell, I don't think people are using this to get to a destination along the road itself. They are using it to commute. Milton's plans call for lowering speed limits. This will most certainly increase traffic in the area.
As far as the mixed use... I don't think Alphareta's planned MU's are as interconnected or have the roads planned that you speak of. I don't think it will have the traffic reducing effect you speak of.
-Lee
Alpharetta's planned MUs are not interconnected and to think that a large percentage of shopping and employment is going to take place within the MU is a pipe dream. Furthermore, the businesses within the MU will need traffic from the outside to sustain themselves.
Michael,
One thing we can agree on is downtown Roswell's charm. I love the way it is offset from Hwy 9. The sereneness of the big old trees and the character of the renovated houses lures one out of the car and invites one to linger all day. With a little creative thinking, we could have had that in Alpharetta too. Many of my neighbors fought for it. ...But the planners knew better.
Think about the way Canton Street (between Mayfield and Academy) used to look before all the old houses were demolished and the big old trees cleared out. We should have renovated those old homes and made that our central shopping district. We could have provided bricked and landscaped meandering alleyways to the back entrances of those businesses fronting Hwy 9.
This plan would have blended beautifully with the few remaining private homes on Canton who chose not to sell out, including everyone's favorite old tin-roofed yellow house with the gorgeous old ginko out front.
Instead, local residents filling the public hearing til well into the night could not convince our City Council, who, at the end of the night, told us we would "thank them in 10 years" for the high density townhomes and condos they were foisting upon us. It has been 5 years and we're still down for the count, but instead of old homes and trees, we have two adjacent PVC farms, one in a mud pit, surrounded by rickety, half-painted "beauty fences" with pickets falling out. (Oh, nevermind, the pickets have been "fixed." The fallen pickets have been nailed back up but this time with visible muddy fingerprints on them. They must not have been able to find one of the pickets so they replaced it, but left that lone picket unpainted on the otherwise white-washed fence.) It's very lovely.
Why would they do this ,you ask? We wonder too. I think it has something to do with being "green" but not "green" in the way you might think. They could have even had their coveted townhomes, but placed them in back of the shops, sort of like Roswell has done with their new Providence development. Nope. They wanted a tunnel of townhomes on either side of the road right up next to the road where no vegetation could possibly see sunlight.
The only other reason I can think is that at the time they were working on their now-killed "City Center" plan. Perhaps someone's ego wanted the City Hall to be the crown jewel of the shopping district? Don't know, just guessing. Roswell has separated their City Hall away from the shopping district and I think the concept works well.
My neighbors now affectionately call Canton Street "Eyesore Corridor." Thank goodness the owners of everyone's favorite yellow home chose not to sell out or that one little bit of history would have been torn out too. I'm sure it will succumb one day too. We'll never have a Bulloch Hall in Alpharetta but it would have been nice to preserve what little we do/did have.
Lee, I'm moderately familiar with the Hwy 9 section. I think the added lane capacity in the areas where it is currently 1 lane will reduce enough bottlenecks to meet the traffic demands for some time even with the shrinking lane widths. Also, we might not have as many people driving on the road in 5-10 years if gas continues to stay expensive. (that goes back to some of our previous discussions)
Kim, you're absolutely right that Alpharetta has made a lot of mistakes. The downtown area has soo much potential. But, you have to remember the mindset of (virtually) everyone in public office and in the community at large in the mid-late 90's and early 2000's when many of the decisions that were to shape the heart of Alpharetta's current form. The general mindset was not one of real placemaking but rather unbridled development for the "green" minded. Simple projects were given the greenlight without much concern for what they would do to the context of the area. There was not a lot of responsibility nor was there any real type of community involvement.
The atmosphere today in most communities is much different. There is an almost overwhelming attention to public opinion. Now, does that mean that everyone gets what they want? Absolutely not but everyone does generally get an opportunity to be heard. The best and most sensible ideas are beginning to rise to the top and developers don't have much choice but to listen. They won't have jobs if they don't. Mistakes will be made but the post 2010 development will be much more community minded and austere than the pre 2007 development. (is that a generalization about a generalization?)
I'm talking macro trends rather than specific projects btw.
Ha! I can tell by your comments that you don't live in Alpharetta.
First, these decisions about Canton Street were not made in the 90's and early 2000's. These decisions were made in 2006! There was <b>much</b> community involvement, so much so that it filled City Hall and comments lasted well into the night.
Secondly, there was significant community input on the 2003 Downtown Plan. Ironically, in the dark of the night, the City and Community Development saw fit to override the citizens and came up with a "Historic Downtown Incentive Zoning" overlay in 2005. No fanfare. No one knew. This is the vehicle that enabled the decisions that were made that night in 2006 and why the community was so outraged. The great irony, of course, lies in the naming of the overlay... "Historic Downtown..." while they were, in fact, tearing down historic old homes! They were into "placemaking" alright. They just had their own vision that was going to trump the community, <i>no matter what!</i>
<i>"There is an almost overwhelming attention to public opinion. Now, does that mean that everyone gets what they want? Absolutely not but everyone does generally get an opportunity to be heard."</>
This made me spew coffee. As I said, you obviously don't live in Alpharetta. I don't recall if it was this 2006 hearing or a later one that was well-attended, but it was the catalyst for the "3 minute rule." Rumor has it that one of the councilwomen didn't like getting home late, so they began limiting each citizen to only 3 minutes.
You may tend to think that this 3 minutes is a guideline, but I can assure you that it is a rule that is enforced. Citizens are routinely reminded of it. On another issue, I and another neighbor went to comment on a matter at the end of a Council meeting. It was a short meeting that night and I think the meeting was ready to end at 8pm. When citizen comments were opened up, my neighbor was reading her prepared remarks. It was obvious that she only had 2 sheets of paper so it wasn't going to last long into the night. When that buzzer went off, the mayor had heard enough, and in fact cut her off in mid-sentence. This is status quo, not an anamoly, at least in my experience. Or maybe it happens only when it is something they don't want to hear.
One peek at the state's Zoning Procedure Laws shows that the spirit of the law is to allow equality between developer and the public, but this isn't how it is done in these here parts. In 2011!!!!
You make the argument that citizen input is highly regarded these days but the experience of the old-timers in Alpharetta begs to differ. They claim that "it didn't used to be like this." Many people have verbally commented to me that it is a waste of their time to speak up at City Hall. The people in my community are really jaded about how they've been treated as of late.
What I have seen is regard for so-called "public input" when it can be used nebulously to support a forgone conclusion. But when it comes to true public input, especially when it goes against the flow, they want to shut it down.
I hope your experience improves. It certainly has in other parts of the country and county. I definitely wouldn't be happy with what's happened with the downtown center of Alpharetta but I can assure you that the current outcome was influenced by policies set in place long before 2006.