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Opinion Transportation

CNU’s 2018 Transportation Summit: A New Traffic Model for Brent Spence Project

The underlying assumption of the Brent Spence Bridge project is that the level of congestion warrants relief with a new bridge and freeway expansion. The problem of congestion will be solved with new freeway capacity. However, that simple formula does not account for all the costs of the freeway expansion or the benefits not running a freeway through the urban core.

Two important pieces missing from the Brent Spence Bridge project cost/benefit analysis are the value of urban land and induced demand. As noted in a prior article, urban land is valuable. The sustained growth in Over the Rhine is local proof of the national trend that people want to live, work, and play in cities. Proponents of the bridge expansion project assume that the congestion relief is worth the price tag and loss of urban land for the next 50+ years. But what if the congestion relief is ephemeral?

Others in Cincinnati have described induced demand. To reiterate, it is the propensity for freeway lanes to fill to capacity once they are created. New capacity creates new demand. Decreasing the cost of driving with shorter, faster commutes, increases the number of drivers. Road expansions are intended to expand capacity and reduce congestion; however, new freeway capacity quickly fills up and becomes just as congested as before.

There appears to be no upper limit at which enough lanes eliminate capacity. The Katy Freeway in Texas provides the case in point. First constructed in the 1960s, it was six to 8 lanes wide. A $2.8 billion expansion project finished in 2011 that expanded it to one of the widest freeways in North America at 26 lanes: At one segment each direction has 6 lanes of through traffic, 4 feeder lanes, and 3 HOV/toll lanes. Travel times decreased immediately after the expansion, and in 2012 the Katy Freeway was hailed as a success story. However, by 2014, travel times increased 30 percent during the morning commute and 55 percent during the evening commute. $2.8 billion and 18 extra lanes improved traffic for three years, then made it worse than before the project. It achieved congestion relief for less than three years.

The predicted benefits of the Kary Freeway did not last. Cincinnati should learn from that lesson and include the effects of induced demand in the Brent Spence Bridge expansion cost/benefits accounting. The previous design did not adequately analyze induced demand.

Part of the reason that the project did not include induced demand as part of the analysis is that the software used to model traffic volumes is not up to the task. The model, called Static Traffic Assignment (STA), was designed to run on computers from the 1970s. Since you are reading this article on a computer there is no need to explain how much computers have changed in that time. There have been upgrades to the STA software but it retains the same fundamental architecture. STA produces usable predictions for daily traffic volumes but not for peak demand (rush hour). Accurate predictions of peak demand are necessary to understand induced demand.

There are two problems with STA that provide inaccurate peak demand forecasts. First, STA assumes roadway segments are independent, so that a problem in road segment “A” will not impact road segment “B.” In reality, congestion in one road segment does impact adjacent segments. Second, STA allows modeled traffic volumes to exceed capacity. If the model predicts capacity beyond what a given freeway can support, the model will queue vehicles up “outside the model.” In reality, those cars queued “outside the model” are either stuck in traffic or they’ve left the freeway and are taking surface roads to work.

The interstate system is a network that seeks equilibrium. If there is congestion in the network, drivers will avoid it. If there is capacity in the system, drivers will fill it up. The current Brent Spence Bridge project was modeled with STA. STA does not look at the network holistically. It either breaks up the system in segments or moves extra traffic outside the model. The failure to look at the system holistically makes it difficult for STA to predict where induced demand will come from and how intense the demand will be.

A better model now exists to forecast traffic. Called Dynamic Traffic Assignment (DTA), it is a more sophisticated computer model designed to run on contemporary computers. DTA holistically models an interconnected network in equilibrium. If a bottleneck causes a traffic backup, DTA assumes traffic will divert to surface roads rather than move outside the model.

The 2018 CNU Transportation Summit on Highways to Boulevards featured the presentation of a recent paper on DTA. Overall, DTA is a more powerful modeling tool that can better analyze effects on complex systems. There are five vehicular bridges over the Ohio River in Cincinnati, plus the two I-275 bridges. The traffic model must accommodate the regional impact of the bridge expansion on traffic, including the effects of induced demand. This is doubly important if the Brent Spence Bridge expansion is tolled and other bridges are not.

A DTA model of the Brent Spence bridge project will better show the impact of additional vehicles on local streets. Civic leaders in Cincinnati and Covington should have a better accounting of how moving an additional 50,000 vehicles per day through the urban core will affect their street networks, which must be paid for with city tax dollars.

Would it make sense to spend five years building the expansion project if the congestion relief dissipated within five years? Before moving ahead with such a large and expensive project there must be a full accounting of the costs and benefits. Particularly relevant to CNU, the loss of urban land has not adequately been included in the cost of the project. The benefit of congestion relief is diminished by induced demand. There are new tools at hand to better tally up these costs and benefits. A project the size and scale of the Brent Spence bridge expansion project requires a full and transparent accounting of the costs and benefits to move forward.

This is a guest article by Chris Meyer reporting on the 2018 CNU Transportation Summit. CNU and CNU Midwest are content partners with UrbanCincy. Chris is an Architect at Hub + Weber, PLC

If you would like to have your thoughts and opinions published on UrbanCincy, simply contact us at editors@urbancincy.com.

Categories
Opinion Transportation

CNU’s 2018 Transportation Summit: Lessons for Greater Cincinnati

CNU’s 2018 Transportation Summit was September 16-17 in New Orleans. The purpose of the summit was to bring together people focused on the revitalization of urban neighborhoods disrupted by freeways. In attendance were people from Massachusetts, California, Colorado, Texas, Wisconsin, Washington DC, and two members from CNU Midwest, Chris Meyer and Brian Boland. There were many takeaways from the summit but three lessons seem applicable to Greater Cincinnati.

The first is that freeways and urban fabric are incompatible. Urban fabric in Greater Cincinnati typically consists of fine-grained parcels, 2-5 story buildings, and a dense street with grid pedestrian-scale streetscapes. Urban fabric is fundamentally sized for people. The 19th century blessed present-day Greater Cincinnati with an abundance of high-quality urban fabric. A minor takeaway from the transportation summit was that other cities would be jealous if they knew what we have.

Freeways are scaled for cars and trucks. They are always interruptions in the urban fabric. They break up the street grid wherever they pass through it and form barriers to people passing. The urban fabric for blocks around a freeway is degraded not only by the dirt, noise, smell, and ugliness but also by the profusion of vehicles they concentrate and deliver into the urban fabric. This is true for greater Cincinnati along the I-75, I-71, and I-471 corridors.

Freeways are a necessary part of the urban economy but they are incompatible with the urban fabric. It was a mistake to run them through central cities. Dwight Eisenhower, the father of the interstate system, certainly thought so.

Multiple people at the summit noted that urban freeways are “monuments to racism.” That’s obviously the case in New Orleans. In Cincinnati, the West End neighborhood is physically gone but the Kenyan Barr photo exhibit, currently showing at the University of Cincinnati, illustrates the neighborhood destroyed by I-75. Ninety-seven percent of the residents were black.

A second lesson from the transportation summit is that urban fabric is valuable. Anyone familiar with CNU understands that. What was new is that urban fabric can be more valuable than the freeways running through it. Implicitly or explicitly, a big part of the argument to remove freeways, be it Denver, Oakland, or Austin, is to free up land for profitable new development.

The same principle applies to Cincinnati. The value of land with urban development on it is greater than the same amount of land with auto-centric development on it. The blocks around freeways are almost always taken up with auto-centric development because of how freeway ramps concentrate vehicles in a geographic space. Cincinnati would reap greater economic, tax, and social benefits if the space around Interstate-75 followed urban development patterns rather than auto-centric development patterns.

The third lesson is that the future of urban development doesn’t have to look like the past. When the first Congress for New Urbanism met in 1991, most new development was going to suburbs and central cities were still losing money and population. That has changed. People are moving back to places where they can live, work, and play, without a car. It’s happening in Cincinnati too.

Recognizing the value of urban fabric and the cost of freeways in the urban fabric allows people to recalculate the costs/benefits of future transportation projects. Two high-profile Cincinnati transportation projects include the Cincinnati Bell Connector streetcar and the Brent Spence Bridge expansion.

One argument against the streetcar is that it is not “profitable,” so it should be shut down. However, streetcars are compatible with the urban fabric. Most buildings and parcels on the streetcar route have been improved. Streetlife – outdoor dining, social interaction, economic activity – along the streetcar route is as vital as it’s been for decades. The streetcar is a fellow dancer in the sidewalk ballet. It improves the value of adjacent urban fabric, in opposition to freeways that destroy value. A better cost/benefit analysis of the streetcar would include the increased tax value derived from adjacent improved parcels.

The inverse argument occurs with the Brent Spence Bridge project. The primary cost/benefit evaluation looks at congestion. The potential value of restored urban fabric has never been a part of the bridge’s cost/benefit analysis. When they factored the value of urban fabric into the Fort Washington way redesign, they decided to sink the freeway below grade so it could be capped in the future. It’s easy to envision a redesigned bridge project that includes land for new urban fabric, much as the Fort Washington Way project did.

The 2018 CNU transportation summit brought together thought leaders, local activists, transportation professionals, and city designers. A repeated statement at the 2018 summit was that multi-million dollar infrastructure projects should improve the value of places where they are constructed. In Greater Cincinnati, it seems like the value of place is often not considered in the cost-benefit analysis of large transportation projects.

In the past, it was possible to argue that urban fabric had no value, or that its value was equal to auto-centric development. Those arguments can no longer be made in good faith. If Cincinnati is going to capitalize on the wealth of its urban fabric, the value of that fabric must be included when evaluating future transportation projects. If it’s done so accurately, we should be all the wealthier.

This is a guest article by Chris Meyer reporting on the 2018 CNU Transportation Summit. CNU and CNU Midwest are content partners with UrbanCincy. Chris is an Architect at Hub + Weber, PLC

If you would like to have your thoughts and opinions published on UrbanCincy, simply contact us at editors@urbancincy.com.