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I-70 approaching the Arch. // MoDOT Photos.

MoDOT is worried about traffic issues that may result from the replacement of I-70 downtown with an urban boulevard as proposed by City to River. From an STLtoday Road Crew discussion:

Linda Wilson: [MoDOT's] position is that after we build the new Mississippi River bridge downtown, there will still be a demand of 50,000+ vehicles per day to drive the section of highway that runs in front of the Arch. [...] We have told the groups that if they can develop a plan to accommodate how these 50,000+ vehicles can get through, we are open to looking at it.

In response, City to River wrote a blog post with examples of urban boulevards around the world that currently handle 50,000 vehicles per day or more. In all likelihood, however, a re-imagined Memorial Drive will not be burdened with such high traffic volumes.

Conceptual Math

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Road realignments proposed by McEagle’s Northside project may reduce the traffic burden on a new Memorial Drive. // NorthSide.

Take 50,000 vehicles on I-70, then remove the highway and replace it with an urban boulevard. The result is less than 50,000 vehicles on the new Memorial Drive.

The devil, of course, is in the details. How much of I-70 is removed? How do the stub ends of I-70 and I-55 connect to the street grid? Will any other streets get realigned as part of the highway removal project? Only a full fledged traffic study can predict how much traffic would travel along a reworked Memorial Drive. But the answer will invariably be less traffic than there is now. Just like in electrical systems, if you add resistance to a network, some traffic will scatter looking for alternate routes of travel.

Quick Look at Portland

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Waterfront Park and Naito Parkway in Portland, Oregon. Waterfront Park was created from land occupied by a former highway. // freddy and Greg_e.

Portland is one of the most frequently cited cities when it comes to highway removal and for good reason. In 1974, Portland closed and removed the the four-lane Harbor Drive freeway. In its place, the city built Waterfront Park and now enjoys unhindered access to a green oasis and its riverfront.

Prior to Harbor Drive’s closure, traffic engineers warned that closing the freeway would cause unprecedented congestion. The Portland City Council was convinced otherwise. The freeway was closed and… nothing. Traffic appeared to be just as if it were any other day. Sound familiar?

All in all, the worry about how to accommodate traffic from I-70 may well be much ado about nothing.