Will more lanes on I-75 mean fewer traffic jams?

Posted at 9:15 AM, Nov 17, 2015
and last updated 2015-11-17 09:15:20-05

CINCINNATI — Numerous stretches along the 10 miles of Interstate 75 running through Cincinnati will be one lane wider once work on the Mill Creek Expressway Project concludes in 2020.

According to officials with the Ohio Department of Transportation, the construction headaches are an unfortunate but unavoidable consequence of the need for better traffic flow, safer road conditions and less impact on properties sitting near the well-worn 60-year-old transit corridor.

TIMELINE: When will I-75 construction finally end?

Safety is a concern along the city’s troubled stretch of highway: The top two locations for most crashes in the city sit along the stretch between the Western Hills Viaduct and Ronald Reagan Cross County Highway (the scope of the Mill Creek project, roughly).

Wrung fists and curse words aplenty spew as rush-hour commuters sit in I-75 traffic. This is nothing new.

Good thing we’ll have wider lanes soon to make more room. Right?


Not so fast.

If You Build It, They Will Drive

There's no question that the nearly half-billion dollar Mill Creek project's narrow lanes and shifting traffic patterns are contributing to the corridor's current problems, and it stands to reason that the project's completion will mean some of those problems will lighten.

Another part of the logic, though, is to increase the roadway's capacity to better handle the heavy volume of vehicles navigating the busy corridor. Here's a map indicating what specific stretch of I-75 has been or will be affected by construction. A large portion of the stretch is slated to see one more lane in each direction by project's end:

But, as WCPO has previously reported, the idea that widening highways relieves congestion and crash problems might be running out of gas. Studies demonstrating that road widening has the opposite effect continue to line up like cars stuck in traffic.

The buzzword behind this increasingly adopted claim is “induced demand,” and it's basically the “Field of Dreams” approach to America’s love-affair with its second-favorite pastime, the open road: If you build it, they will drive.

Wired’s Adam Mann said the idea is built on the notion that people like to move around, and will do more of it when given the opportunity. This led him to call road widening efforts “fruitless,” pointing to a study by the Property and Environment Research Center, which — in step — called such projects “exercises in futility." The study found a 10 percent increase in road capacity has resulted in a 10 percent increase in vehicle miles traveled in some cities over recent decades.

In other words, adding more lanes resulted in drivers simply driving more.

In a policy brief for the National Center for Sustainable Transportation, environmental science and policy professor Susan Hardy detailed what scientists have learned about the apparent impact of road widening on vehicle miles driving in the U.S. What she found was not promising when it comes to reducing congestion. Hardy’s two key findings were these:

> Increased road capacity leads to more miles traveled in the short term… and even more miles traveled in the long term, leading to as much as a one-to-one ratio between increase in capacity and increase in traffic.

> People aren’t just driving more on the widened road. They’re driving more in general.

Hardy called the science behind the studies she reviewed “sophisticated.” That is to say: They're legit.

Oops, right? If it’s true...

I-75 between Marshall and Hopple (Google)

ODOT spokesman Brian Cunningham said the worry that increasing road capacity leads to higher traffic volume has been around for a few decades. But while he stopped short of throwing out that concern completely, he did question how applicable it is in the case of the Mill Creek corridor, where he said the city is already seeing "gradual" increases in traffic volumes.

Cunningham characterized the lane additions sort of like a game of catch-up.

"This is the first major rebuild the highway's seen since it was built (more than) 50 years ago," he said. "We're not handling the traffic volumes we're seeing today, and (the new lanes) also anticipate what we expect as far as future increases go."

As for hard numbers, though, Cunningham said ODOT hasn't done a quantitative study on how the extra lanes will or won't increase vehicle miles traveled through the Mill Creek corridor.

Traffic's a Mess

Traffic congestion is a mind-bogglingly complex phenomenon, with the Federal Highway Administration identifying inadequate capacity as just one of at least seven factors contributing to congestion, many of which are often in play simultaneously.

See the FHWA's full breakdown here.

Adding to the complexity, Cunningham said, is that the Mill Creek Corridor — as well as the adjacent and equally troubled Brent Spence Bridge — serves a high volume of both local (i.e. Cincinnati-bound commuters) and cross-country traffic. Including the Brent Spence, the area is a node connecting traffic flowing to and from 10 states, all told.

READ MORE: Will KY's Bevin bring progress or pause to Brent Spence Bridge project?

This means most if not all of the highway administration's congestion factors are consistently at play, requiring a variety of solutions. That's a characteristic the Mill Creek Expressway Project seems to have in mind: Increasing capacity is only one upgrade crews have or will undertake. The work also includes much needed improvements to aging interchanges and overpasses along the stretch.

But Cunningham emphasized that, despite the choice to drive being made primarily out of convenience (hence drivers' continued fury over traffic "headaches"), the Mill Creek project is as much, if not more, about making the corridor safer for drivers as it is about easing congestion problems.

"You're already running on an inefficient network that is crumbling," he said, not just referring to the quality of the road surface but also its foundation below.

In the meantime, like so many Tri-State commuters sitting in construction-induced delays, we'll have to wait to see what's ahead.