Ponder the happiness of our State Street corridor while reading about "The Causes of Traffic and Congestion."

File under:

"Attempting to address congestion with solutions that make it easier to drive can make the problem worse by continuing to make the car the preferred way to get around."

Alternatives, anyone?

The Causes of Traffic and Congestion, by Andrew Price (Strong Towns)

There are many misconceptions in my local conversation about what does or does not induce motor traffic. Some of these misconceptions are:

• Single family homes do not increase traffic. If all we build are single-family homes, this will forever stay a quiet neighborhood.
• Commercial development does not increase traffic, because it does not add more residents.
• Congestion is bad, and we should treat avoiding it as a priority.

Let's dive into it: traffic, what causes it, and what we can do about it.

The Role of the Street Network
The largest contributor to congestion is the hierarchical road network. This is where you have local streets feed into collectors that feed into arterials that feed into highways.

The Strong Towns article on Dealing with Congestion explains why this is bad. We are funneling all traffic through a small number of streets, giving us a lower vehicle capacity as well as fewer redundancies for when things go wrong (creating a fragile road network where one clog can grind traffic to a halt), and artificially spaces things out by reducing what you can reach in a given distance (sometimes stupidly so as in the case where two houses share a backyard despite their front doors being 7 miles apart).

A highly connected street network (this can mean a grid, but can also take non-geometric forms such as the street network of a medieval city) is better because there are a ton of redundancies (a street closure does not matter if you have countless alternative routes from A to B) and distances are shorter as you can take a more direct route from A to B. Because the load is distributed over the many redundancies, we are no longer funneling all of the traffic over a small handful of collectors or arterials, so you are going to encounter less traffic along your way, even if all else (population density, amount of travel) remains equal.

Designating a main thoroughfare, with higher speed and greater capacity, to funnel traffic through is bad, even if it is part of a street grid. This thoroughfare will attract all of the traffic until it is so congested that it no longer offers a speed advantage over alternative routes (such as parallel side streets), and all people will do is complain how congested it is. This holds true any time we deal with funneling a flow: getting all cars to take the same road, asking all spectators to leave through the same stadium door after a sports game, making all travelers at the airport to go through a single security line, pushing all commuters onto a single transit line, getting all permit approvals to flow through a single queue, and so on. It does not take many people for it to feel crowded when everyone is concentrated in one place.

Snipping through to the conclusion.

Is congestion really a problem?
At the end of the day, we should not worry too much about congestion or traffic. Congestion is part of the solution, not the problem. Congestion is feedback that we have built a place people want to be. The response to congestion should be to allow that Mexican restaurant to open up 3 blocks away rather than 2 miles away. To create bus lines and bike lanes that give people alternative ways to get around. The incorrect response to congestion is to build faster and wider streets, because that just reinforces car dependency and all of the negative consequences that come with it.

To summarize:

Development can add traffic. However, development that brings amenities and people closer together and reduces the need to travel so far can actually reduce traffic. With a mixture of uses, you can achieve a high population density with very little motor traffic.

A highly-connected street network (either a street grid or organic) with many redundancies better distributes the load of traffic and is more resilient to disruptions.

Designated thoroughfares and bypasses create an illusion of traffic because they funnel the traffic through a single point (and with this comes the fragility of a single point of failure that can bring down the system).

Attempting to address congestion with solutions that make it easier to drive can make the problem worse by continuing to make the car the preferred way to get around.

We should not worry too much about congestion, because it creates demand for other modes of transportation and for amenities to be closer.

Stuck in traffic? Pay close attention: "Here’s how 'induced demand' works."

Graph courtesy of Vox.

They're calling it CityLab University for a reason. The linked article isn't a meme, and it probably can't be read in the time it takes to skim a News and Tribune article.

However, your diligence will be rewarded.

Along with the daily output at Strong Towns, CityLab is essential reading for those seeking to understand how these things work. All our public officials should be reading these essays and others like them.

Are they?

CityLab University: Induced Demand, by Benjamin Schneider (CityLab)

It’s time again for “CityLab University,” a resource for understanding some of the most important concepts related to cities and urban policy. If you like this feature, have constructive feedback, or would like to see a similar explainer on other topics, drop us a line at editors@citylab.com.

When traffic-clogged highways are expanded, new drivers quickly materialize to fill them. What gives? Here’s how “induced demand” works.

With 26 lanes at its widest point, the Katy Freeway in the Houston metro is the Mississippi River of car infrastructure. Its current girth, which by some measures makes it the widest freeway in North America, was the result of an expansion project that took place between 2008 and 2011 at a cost of $2.8 billion. The primary reason for this mega-project was to alleviate severe traffic congestion.

And yet, after the freeway was widened, congestion got worse. An analysis by Joe Cortright of City Observatory used data from Houston’s official traffic monitoring agency to find that travel times increased by 30 percent during the morning commute and 55 percent during the evening commute between 2011 and 2014. A local TV station found similar increases.

The Sisyphean saga of the Katy Freeway is a textbook example of a counterintuitive urban transportation phenomenon that has vexed drivers, planners, and politicians since the dawn of the automobile age: induced demand.

KEY POINTS

• In urbanism, “induced demand” refers to the idea that increasing roadway capacity encourages more people to drive, thus failing to improve congestion.
• Since the concept was introduced in the 1960s, numerous academic studies have demonstrated the existence of ID.
• But some economists argue that the effects of ID are overstated, or outweighed by the benefits of greater automobility.
• Few federal, state, and local departments of transportation are thought to adequately account for ID in their long-term planning.

SUMMARY

Nearly all freeway expansions and new highways are sold to the public as a means of reducing traffic congestion. It’s a logical enough proposition, one that certainly makes plenty of sense to anyone who’s stuck in traffic: Small communities served by small roads grow bigger, and their highways need to grow with them. More lanes creates more capacity, meaning cars should be able to pass through faster. But that’s not what always happens once these projects are completed.

Just as with the Katy Freeway expansion, adding new roadway capacity also creates new demand for those lanes or roads, maintaining a similar rate of congestion, if not worsening it. Economists call this phenomenon induced demand: When you provide more of something, or provide it for a cheaper price, people are more likely to use it. Rather than thinking of traffic as a liquid, which requires a certain volume of space to pass through at a given rate, induced demand demonstrates that traffic is more like a gas, expanding to fill up all the space it is allowed.

Transportation researchers have been observing induced demand since at least the 1960s, when the economist Anthony Downs coined his Law of Peak Hour Traffic Congestion, which states that “on urban commuter expressways, peak-hour traffic congestion rises to meet maximum capacity.”

This list is helpful, too.

Further Reading

“Highway Boondoggles 3”

“The Fundamental Law of Road Congestion”

“Increasing Highway Capacity Unlikely to Relieve Congestion”

“online.trb.org/doi/abs/10.3141/2653-02?journalCode=trr" style="box-sizing: inherit; color: black;">Closing the Induced Vehicle Travel Gap Between Research and Practice”

“Generated Traffic and Induced Travel: Implications for Transport Planning”

Stuck in Traffic: Coping With Peak Hour Traffic Congestion

David Duggins answers: "The scope of work is the entire downtown street grid."

Yesterday, in the wake of the city's announcement of a street study consultancy with Jeff Speck, the Courier-Journal's Grace Schneider wrote about the pivotal Board of Public Works meeting Tuesday, highlighting comments made by David Duggins during the session. One in particular was significant.

"Duggins said the city would not implement any recommendations that would reduce traffic capacity."

Using this as a jumping-off point, I asked four questions of Duggins, e-mailing them to him. He responded promptly yesterday afternoon. The questions were:

1. If "the city would not implement any recommendations that would reduce traffic capacity," what's the point of bringing Speck in?

2. Grace Schneider wrote, "Speck tweeted Tuesday morning that he’s excited to work in New Albany and that his work “won’t be a ‘traffic study.’ But traffic will be studied.” Didn't the mayor insist there had to be a traffic study before considering any modifications?

3. Customarily we'd be hearing John Rosenbarger comment publicly on these matters. Who is riding point for city government when it comes to the Speck study?

4. Most of us have known about it for a while, but was Grace's article the first mention of the $2.5 million in federal money available to implement the recommendations (assuming the aforementioned and disturbing disclaimer that they don't reduce traffic capacity)?

Here are Duggins's answers. It strikes me as curious that John Rosenbarger's name isn't explicitly mentioned; perhaps now that he's achieved the culmination of his planning career by implementing a Main Street project designed to increase the value of his Main Street home at the piddling expense of reducing the value of mine and others on the Interstate Thru Highways otherwise known as Spring and Elm, he'll step graciously (read: the fuck) out of the way and let progress come to other areas of the city north of his mailbox, absent his malignant backroom influence.

A boy can dream. In New Albany, it's often all we have.

---

Roger,

I am happy to answer questions you have, and I am glad to clarify Grace's understanding of my comments. Also please ask me to clarify any item that you may be unclear about before posting.

Grace did not quote me accurately or ask a follow-up question to clarify her understanding of the plan. I said that Speck would not make recommendations that reduce the total current capacity of the grid. His recommendations will re-direct traffic flow and patterns throughout the entire grid. So to be more clear traffic may be reduced on a certain street but increased on a less used street. The scope of work is the entire downtown street grid.

The Comprehensive Traffic Corridor Plan is a combination of Speck's planning and recommendations for the corridor, with information provided by the study portion completed by Nelson/Nygaard Consulting Associates (Engineering Firm). The Mayor is looking at forming a local advisory group to help coordinate and gather information that will be used in the plan. The Mayor has stayed consistent in the message that the corridor will be affected, and that we need expert analysis and recommendations to make any changes and how to proceed.

Mayor Gahan is the obvious leader of this project, but will be helped by myself and the rest of the Redevelopment Staff.

The Federal Aid project is the 2.5 million that was mentioned, and can be used for corridor improvements including traffic calming, striping, medians, turn lanes, and traffic signals.