“When we add capacity, we induce more driving. So there’s sort of a vicious cycle: We widen roads, people drive more; we widen roads, people drive more.”

As one component of this blog's enduring commitment to public service, here's another of our periodic efforts to help readers understand induced demand.

Yes, we know it's impossible to stockpile campaign contributions by not awarding engineering, paving and road construction projects.

Right, Ed Jolliffe?

Here I go again.

Study calls for curbing congestion by building fewer roads, by Eric Hamilton (University of Wisconsin-Madison)

Cities clamor for new development, with its promise of new housing or economic opportunities. Then comes the unwelcome side effect: congestion.

Popular new attractions or dozens of new apartments mean more travel in the neighborhood. To cope, cities typically require developers to add highway capacity for many new car trips, plus the parking those cars need, or pay a fee so the city can make those improvements in their stead.

The catch is, all those new roads might make things worse.

“When we add capacity, we induce more driving,” says Eric Sundquist, managing director of the State Smart Transportation Initiative (SSTI), a transportation think tank housed at the University of Wisconsin–Madison. “So there’s sort of a vicious cycle: We widen roads, people drive more; we widen roads, people drive more.”

SSTI and the UW–Madison-based Mayors Innovation Project recently released a new report arguing for a different approach that incentivizes diverse ways to travel to and from new developments. By funding public transportation, limiting parking and preserving the walkability of neighborhoods, Sundquist’s team argues, cities and states can reduce congestion better than if they only plan for cars.

The same solutions can help cities meet their policy goals, such as reduced emissions or more equitable access to services for residents.

“We look at the gap between policy goals on the one hand and the way decisions are being made that actually make things happen in the real world,” says Sundquist. “Often you have great policy goals, and then you have a bunch of rules of thumb that are still basically what was set in the ’50s during the interstate era.”

The report is designed to help cities set requirements for developers on managing the transportation impacts of their projects, using a menu of measures designed to minimize the need for driving. The goal is to promote sound development, reduce regulatory burdens, keep cities livable and avoid gridlock. SSTI calls its approach “modern mitigation.”

“The idea is, let’s first try to reduce the amount of driving that we’re going to generate in the first place before we add supply, and only add supply if we absolutely need to,” says Sundquist.

For example, adding housing as part of a new hospital development could mean fewer car trips by staff, who might choose to live close to work. Another system might subsidize bus passes for employees of a new office park, so those living along bus lines skip the car more often.

Employers have long adopted such demand-reduction methods to ease rush hour. In recent years, some cities have begun codifying similar mitigation rules to promote fewer and shorter car trips, especially those taken by a solo driver.

The SSTI report takes as examples demand mitigation endeavors in cities like Cambridge, Massachusetts, where fewer than 40 percent of employees drive to work alone in certain areas. Cambridge promotes systems like subsidized transit passes and shuttle services.

The core of SSTI’s proposal has developers propose a set of measures to reduce the demand for solo car trips depending on the size and other characteristics of their planned project. Cities then agree to the set of measures, make sure they work as intended and, if need be, enforce any penalties for noncompliance.

Shifting from conventional mitigation to modern mitigation may not require changes to laws in many municipalities, says Sundquist, who served on the Madison Plan Commission for seven years. The guidance given by such committees to developers is often a codified set of policies, rather than laws, with considerable flexibility.

Perhaps harder, Sundquist says, is shifting the focus away from adding roads toward reducing the need for those roads. Car-centric policies have been in place for a half-century or more and have in many cases made alternative policies harder to implement. The first step, he says, is to change course.

“We’re dealing with problems set in motion decades ago. “When you’re in a hole, quit digging.

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

Carmageddon in Atlanta -- or maybe not, because "predictions of terrible traffic in the wake of even major disruptions to the road system are almost never realized."

To hell with facts -- we need more traffic lanes!

Carmaggedon stalks Atlanta, by Joe Cortright (City Observatory)

Why predicted gridlock almost never happens and what this teaches us about travel demand

It had all the trappings of a great disaster film: A spectacular blaze last week destroyed a several hundred foot-long section of Interstate 85 in Atlanta. In a city that consistently has some of the worst traffic congestion in the country, losing a key link its freeway system could only mean one thing: Carmageddon ...

 ... The prospect of gridlock makes for great headlines and local TV news stories, but as it turns out, predictions of terrible traffic in the wake of even major disruptions to the road system are almost never realized.

One of the most famous instances of this phenomena was in Los Angeles. In 2011 and 2012, the state highway department closed a 10 mile stretch of Interstate 405 on several weekends to rebuild overpasses. The media was awash in predictions of Carmaggedon. But surprisingly, nothing of the kind happened. As Brian Taylor and Martin Wachs explain in an article in Access, people mostly avoided taking trips in the area, or chose alternate routes, with the effect that traffic was actually much lighter than normal. They report that “Rather than creating chaos, the first closure greatly reduced traffic congestion.” Taylor and Wachs explain that “crying wolf” about likely gridlock depressed trip-taking in the affected area, but that effect faded as travelers realized things were nowhere as bad as predicted ...

Here, there, everywhere: "Creating real transportation options" for all residents.

Specifically in this case, Denver, but the implications for Louisville metro are fairly clear.

Is the ORBP boondoggle finished yet?

Locantore: It's not about congestion; it's about freedom, by Jill Locantore (Denver Post)

... ultimately, congestion isn't the problem we should be trying to solve. The bigger problem is that many Denver residents don't have any options other than driving to their daily destinations. Automobiles have long symbolized freedom in the American imagination. Yet in our devotion to building communities oriented around driving, we've engineered the ability to walk, bike, or take transit out of many of our neighborhoods. Now here we are enslaved to our automobiles, obsessed with fueling them, parking them, and making sure they don't get too crowded on the roadways.

Traffic congestion, traffic safety, and how NOT to be confused about them.

As you consider the considerable merits of a two way street grid in New Albany, and find it hard to wrap yourself around some of the things we've been saying, read the two paragraphs below.

Jeff Speck provides pertinent answers for you, and just because Bob Caesar can't grasp them, it does not mean you can't.

Jeff Speck: Walkable City / Slideshow (Thinking In Practice)

You mention that building more roads in fact leads to more congestion. An interesting notion – could you elaborate on that?

In constrained road systems, the principle constraint to driving is congestion. If you allay congestion by building more roadway, people drive more, and quickly fill up the new space. This is identified as the Fundamental Law of Traffic Congestion, and not disputed among thoughtful planners.

What are some of the major challenges in the advocacy of walkability and pedestrian-friendly environments? What do you usually come up against in your work?

The principal challenge is overcoming the confusion, in fact, that surrounds traffic congestion, as well as traffic safety. Convincing populations that new roads will not solve their traffic woes is possible, but convincing the municipal engineers, who were educated differently (and wrongly) can be harder. They were also taught, in the US at least, that the way to make roads safer is to make them wider, with fewer obstacles like trees. Recent studies show that this, too, is wrong. Wider, simpler, clearer roads cause people to drive faster, and dramatically increase the likelihood of death by automobile.