The STROADs of North Fulton

This is a cross-post from my monthly column, Community Design Matters, with The Current.

Roads are inherently meant to connect places.  Ideally, they are higher speed with very few intersections, entrances and distractions.  They have wider lanes and more forgiving curves to provide added safety.  They differ significantly from streets which are meant to create places and capture and build upon the value in those places.  Well designed streets are typically straight and have many intersections.  They have narrower lanes and have sidewalks and sometimes bike lanes.  Turn lanes and acceleration lanes shouldn’t be present.  Traffic on properly designed streets is slower and it mixes with other modes such as pedestrians, bicyclists and pubic transportation.

Examples of properly functioning streets and roads in North Fulton are few and far between.  One street that comes to mind is Canton Street between Magnolia St and Woodstock Rd.  It functions very well as a street by taking multiple modes safely through an environment that defines a place. It is a destination point which is usually where streets are present.  A well functioning road (although not named a road) is actually Marietta Hwy from Roswell to East Cobb.  This road provides a high speed and efficient route from one destination to another with minimal interruptions from intersections, incoming/exiting traffic and shopping centers.  You can safely drive 50+ mph until you near the Avenue East Cobb or the Historic Square.  There are others that function well but most of our streets and roads are actually a dangerous and economically handicapped combination of the two.  

Chuck Marohn of StrongTowns.org has coined the term STROAD to describe a “street-road hybrid” which performs poorly at both functions.  Chuck calls a STROAD “the futon of transportation alternatives. Where a futon is an uncomfortable couch that also serves as an uncomfortable bed, a STROAD is an auto corridor that does not move cars efficiently while simultaneously providing little in the way of value capture.”  You can find STROADs all over North Fulton.  Any time you are driving between 30 and 50 mph, you are likely on a STROAD.  

Some of the more prominent STROADs here in N Fulton are Old Milton Parkway, Mansell Rd, Alpharetta Hwy (especially between Historic Roswell and Hembree Rd) and the grand daddy of all N Fulton STROADs, Holcomb Bridge Rd.  The constant barrage of shopping plazas, gas stations, subdivisions and intersections along roads that are supposed to move people from point A to point B eliminates much of the fast, efficient movement that roads should provide.  Couple the transportation issues with the fact that what we find along our STROADs should actually be concentrated along properly designed streets and you have a recipe for complete and utter inefficiency with a side of unnecessary danger.  

We deck our STROADs out with all the infrastructure necessary for a highly productive street but the revenue generated from the uses lining the STROAD in many cases does not support the maintenance of the infrastructure past one life cycle.  The combination of highway road geometries like wide lanes, turning lanes, merging and deceleration lanes and frequent traffic signals creates an environment ripe for crashes.  Any traffic engineer will tell you that one of the biggest culprits for collisions is speed differential.  When cars are traveling in the same space at differing speeds, you get crashes.  The STROAD is the Mecca for these types of scenarios.  All traffic is forced onto the STROAD from our subdivisions and shopping centers.  All traffic must leave the STROAD to get to it’s destination.  There is no common departure and arrival.  Everyone has a different departure and arrival point along the way.   

Mix a STROAD and pedestrians together and look out.  One of the most infamous stretches of STROAD in the nation is Buford Hwy south of I-285 where there is an intense mix of auto and pedestrian traffic.  Between 2000 and 2009, at least 22 pedestrians died along that stretch of Buford Hwy.  Here's a very interesting video on that road:

Fortunately, North Fulton does not have a location of that nature.  However, there is one very concerning spot that does come to mind.  That is Holcomb Bridge Rd just west of GA 400.  With the amount of illegal pedestrian activity at that intersection, we are one misstep away from a fatal collision.  That area needs a design makeover yesterday and these signs in the median aren't going to cut it.

In order to build stronger towns, safer places and more desirable environments, we need to begin to focus more on points A and B and less on getting people to what’s between them (usually strip malls, gas stations, car dealers).  We need to build more productive streets, like Canton St, and more efficient roads, like Marietta Hwy that will capture value where it should be captured and get people between destinations efficiently and safely.

This month’s column borrowed heavily from the ideas of Chuck Marohn with StrongTowns.org.  If you are interested in hearing more from Chuck, he will be speaking on April 25th at Town Hall | Roswell.  For more info on that event or to register for it, click here.

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Quote of the Week: Grids vs Arterials

Overall, a gridded street network of two-lane roadways can accommodate both pedestrians in addition to much higher volumes of vehicles as compared to the large arterial/collector single intersection.  The superiority in capacity even holds when the grid system is compared against the arterial/collector without any pedestrian  accommodations whatsoever.  This research presented results in terms of vehicle delay and vehicle level of service; while not ideal in terms of truly understanding the impact of these large intersections in a complete urban environment, these results should instead be used to clarify many of the misconceptions that conventional traffic engineers have with regard to such large arterials/collectors intersections.   

Additional benefits of the grid system include real-time route decisions, increased levels of walking and biking, reduced vehicle speeds, and  as some recent research is showing, safer roadways for all users.  Critics may point out that the grid system increases overall vehicle delays for through traffic.  The analysis done as part of this study agrees with this assertion; however, the analysis is limited in that it assumes all trips begin outside the grid, travel through the grid, and then exit the grid.

From Supersized Intersections vs Gridded Street Networks: Comparing Capacities & Pedestrian Accommodation

Each week we feature a quote or an excerpt that clearly illustrates the benefits of new urbanist thought. 

Traffic Misconceptions

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