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

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CHART: The Best and Worst States in America for Transit Funding

According to data from the Federal Transit Authority (FTA), the State of Ohio provides some of the least amount of funding for its regional transit authorities of any state in America.

Texas, Georgia and Missouri also provide next to nothing to their various regional transit agencies, but in no other state are transit agencies as reliant on fares and local taxes as they are in the Buckeye State.

When broadening the search to examine transit agencies in the biggest cities across America, it also becomes clear that states like Pennsylvania, Utah and Maryland, Minnesota and Massachusetts invest large amounts of state dollars in transit. Some transit agencies with little state support, however, receive larger sums of money from regional transit taxes and federal aid.

Source of American Transit Funding

Ohio’s three largest metropolitan regions – all with more than two million people – are different in this regard and have the least diverse range of financial support of transit agencies nationwide. For both Columbus and Cleveland, it means that well over 90% of their total revenues come from fares and local tax dollars, while in Cincinnati it is slightly better at 84% thanks to a bit more federal aid.

“In the recession we saw transit service cut while gas prices drove transit demand to record levels,” stated Akshai Singh, an Ohio Sierra Club representative with the advocacy organization Ohio for Transportation Choice. “Roughly all of the state’s public transportation funding now goes to operating rural transit services.”

Honolulu is the only other region in the United States that has 90% or more of its funds coming from just fares and local tax dollars. Cities in other states providing next to nothing also approach this threshold, but do not exceed it as is the case in Ohio.

It recently reported that the Southwest Ohio Regional Transit Authority (SORTA) is one of the best stewards of limited financial resources, when compared to 11 peer agencies across the country. One of the key findings from Agenda 360 report was how little state financial support SORTA receives.

Part of the problem in Ohio is due to state cuts that have reduced funding for public transportation by 83% since 2000. Those cuts have forced transit agencies in the nation’s seventh most populous state to reduce service and increase fares over the past decade.

According to All Aboard Ohio, the state only provides approximately 1% of its transportation budget to transit, while more than 9% of the state’s population lives without a car.

In addition to regional transit, Ohio continues to be one of the most hostile states in terms of inter-city passenger rail. The state remains almost untouched by Amtrak’s national network and boasts the nation’s most densely populated corridor – Cincinnati to Cleveland – without any inter-city passenger rail service.

“When Governor Kasich came to office, the first thing he did was send back $400 million in federal dollars, for the 3C Corridor, on the basis that operations and maintenance would have been too onerous on the state,” Singh concluded. “Today, ODOT is allocating $240 million to build a $331 million, 3.5-mile highway extension through a 40% carless neighborhood on Cleveland’s east side, a staggering $100 million per mile new capacity road, while openly acknowledging they are reducing access for local residents.”

What does the Astrodome mean to the movement to preserve modernism?

After losing at the ballot box, the Astrodome appears to be on life support as pressure mounts to tear down the vacant engineering and architectural marvel. To some this is representative of the ongoing preservation battle being waged on behalf of modernist architecture. To other’s it is purely economics. Should we, as a people, be working to preserve objects from the modernist movement, and how exactly does the iconic Astrodome fit into that equation? More from NextCity:

Has the nation made the Astrodome into a powerful and motivating symbol of modernism’s plight? No, but that actually shows a positive acceptance of the style. Few media reports of the referendum this week even discussed the building’s style, let alone the usual quibbling over appreciation of modern design. Reporters quoted voters more concerned about the cost of the proposed renovation. The vote went down peacefully, without much of the palpable outcry that led to the recent preservation victory for Hilario Candela’s Miami Marine Stadium.


Until its closure in 1999, the Astrodome was the broadcast setting to mainstream sporting events, concerts and oddities like daredevil Evil Knievel’s jump over 13 cars in 1971 and Bobby Riggs and Billie Jean King’s tennis match (the “Battle of the Sexes”) in 1973. Most recently, the mighty structure seared itself into the epic and unresolved recovery narrative of Hurricane Katrina. Thousands of refugee Americans made the Astrodome into a camp in 2005, turning the stadium into a panopticon of despair.