The following article is written by Strong Towns member Joe Cortright, who founded the think tank, City Observatory. The article is republished from the City Observatory blog with permission.


Time for one of our periodic check-ins on our real world transportation pricing experiment in Louisville, Kentucky.  As you recall, we’ve been watching Louisville closely, because just at the end of last year, the city started what amounts to a laboratory experiment in transportation behavior.  Kentucky and Indiana build a new bridge to double the capacity of the I-65 freeway as it crosses the Ohio River near downtown Louisville. At the same time, it put tolls on the I-65 crossing, but not on the nearby Second Street Bridge, an older, four-lane highway bridge that connects Louisville to the Indiana suburbs north of the River.

As we reported in February, the initial month’s worth of data on bridge traffic shows that adding tolls (which run from $1 to $4 for cars) have caused traffic levels to fall by almost half, from about 122,000 vehicles per day to about 66,000.  We included photographs from area traffic-cams that show rush hour traffic on the tolled bridges almost empty, while traffic was fairly thin on the free Second Street Bridge.

The latest phase of our experiment came this past  this weekend, courtesy of “Thunder Over Louisville,” a kind of combined concert, airshow and fireworks display that is held annually. To handle the big crowds that come downtown and afford great vantage points, the city closes the Second Street Bridge. It did so last Thursday.  So we looked to see how this affected traffic levels.  (The festival itself didn’t start until Friday night, so Thursday was still a reasonably typical business day).

As you can see, traffic on the tolled I-65 bridges was still very light.  (This photo was taken about 5 minutes after 5pm on April 20 and comes from the local “TRIMARC” traffic monitoring website.).  The peak direction of traffic is moving away from the camera’s vantage point, on the right hand side of the photo, north-bound, from downtown Louisville.

As noted, the Second Street Bridge was closed, with barricades. This is the bridgehead in downtown Louisville:

What these images suggest is that, even with the nearby free alternative closed, there’s way, way more capacity on I-65 than there is peak hour demand for travel. You can compare these photos to ones we captured two months ago when the Second Street Bridge was open to traffic at rush hour. While ostensibly the crossing was widened from 6 lanes to 12 to eliminate congestion, the real congestion-fighting investment was the decision to ask users to pay just a portion of the cost of widening the road. With tolls in place, drivers have voted with their feet (or perhaps, wheels) that they didn’t really need additional capacity.

The tendency of traffic to disappear when there’s a toll is an indication that people have much more flexibility about when, where, and how much they travel than is usually contemplated in policy discussions or travel demand models.

There’s another point as well. It isn’t just that traffic has shifted to the “free” alternative. It's that, with tolling in place, apparently many other trips just simply evaporated. The tendency of traffic to disappear when there’s a toll is an indication that people have much more flexibility about when, where, and how much they travel than is usually contemplated in policy discussions or travel demand models. The mental model that says traffic levels are some inexorable natural force like the tides, which must be accommodated or else, is just wrong.

Of course, photos of one moment in time (even at the height of what should be rush hour) are hardly the best evidence of how well a bridge is being used.  For that, we need actual traffic counts — the kind of data that would be generated, for example, if you had cameras, and license plate readers and transponder readers on a bridge, which is exactly what we have on I-65. But, while Riverlink (the toll-bridge operator) quickly posted January’s weekly traffic counts on February 1, its website has no new traffic data for the intervening two-and-a-half months. In fact, the Riverlink website which featured more or less weekly press releases since November, contains no new press releases since that February 1 traffic data.

There are many reasons why they might not yet have pulled together the data, and we’ll be watching eagerly to see when it becomes available.  But we couldn’t help but notice a story that appeared in local press just last week. It turns out that the Kentucky Transportation Cabinet has just signed a $300,000 contract with a Florida consulting firm to help it “determine whether the toll revenue generated by the RiverLink bridges is enough to make debt payments on the project’s bonds.” The financing of the widened I-65 crossing (and another beltway freeway crossing several miles to the East) hinges on tolls generating enough revenue to repay the bonds that Kentucky issued to pay for the project. If toll revenues don’t grow fast enough in the years ahead, the state will have to find some other source of funds to make these payments, which could make this particular experiment in transportation behavior a particularly expensive one. Stay tuned!

(Top image from Google Maps)


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