And they have gotten more complicated over time. They can cover entire metro regions spanning across state lines or tackle a small stretch of a suburban roadway. Travel demand models come in different shapes and sizes.
If there isn’t going to be an increase in traffic, how do you justify building two bridges?” “Because I don’t believe they could have gotten approval to build the project if they had not had traffic forecasts that said traffic across the river is going to increase substantially. “I think it was very important,” Renn said. Recently, I asked Renn how important those initial, rosy traffic forecasts of double-digit growth were to the boondoggle actually getting built. Despite them being a legally required portion of any transportation infrastructure project that gets federal dollars, it is one of urban planning’s worst kept secrets that these models are error-prone at best and fundamentally flawed at worst. The Louisville highway project is hardly the first time travel demand models have missed the mark. As a result, the project has been called by Vox, among others, a “boondoggle” of epic proportions. In 2018, a post-construction traffic study showed that cross-river trips decreased by 2 percent from 2013 to 2018. The project is now finished, and everyone in Louisville can see for themselves which prediction was the better one.
“No matter how crazy this project is,” he wrote back in 2013 when that bond-holder study came out, “it always manages to find ways to show that it’s even more wacky than I thought.” Even worse, according to this new study, the combined 12 lanes of river crossings would carry some 4,000 fewer daily trips than just the I-65 bridge did in 2007 alone, completely undermining the argument that Louisville needed these new bridges.Īaron Renn, an urban policy researcher and frequent critic of the Ohio River Bridges project, extensively documented these shenanigans. It concluded that by 2030, the combined cross-river traffic would be just 132,000 trips, some 15 percent lower than the SDEIS had predicted. The other study, this one for potential bond-holders, was far more puzzling. It found that from 2010 to 2013, cross-river traffic had actually fallen by. Two years later, engineering firm CDM Smith looked at what traffic conditions actually had been while the project was seeking approval. Two subsequent studies, however, also funded by the Louisville-Southern Indiana Ohio River Bridges Project, came to a very different conclusion. As a result, the project got federal approval and moved ahead. The implication was obvious: if they did nothing, traffic would get worse. They concluded that the number of cross-river trips would increase by 29 percent. Using a legally-mandated industry practice called Travel Demand Modeling (TDM), the project backers hired an engineering firm to predict what traffic will look like 20 years in the future, in this case, by 2030.
But in order to get approval to use federal funds for this expensive proposition, the project backers had to provide evidence that Louisville actually needed this expansion.