Sunday Video: How Highways Make Traffic Worse

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Vox examines how building more highways just leads to more congestion rather than solving any particular transportation problem.

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Stephen is an urban planner with a passion for sustainable, livable, and diverse cities. He is especially interested in how policies, regulations, and programs can promote positive outcomes for communities. Stephen lives in Kenmore and primarily covers land use and transportation issues for The Urbanist.

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AJ M

Not at all disputing induced demand, and I agree that most urban freeways have a ‘minimum’ level of daytime congestion, but I think this video significantly understates the role of land use and regional planning. If Katy wasn’t robustly pro-growth, or if Katy was growing into a regional employment center rather than a bedroom community, the congestion issues on that segment of I10 could look very different. Given the absence of alterative E/W routes to job centers and a presumably high existing mode share for SOV driving, the daily demand mostly is what it is (certainly congestion shifts time of day for many trips)

A good counter example in greater Seattle is I5 between Everett & Marysville/Arlington. In the absence of I5 expansion across the Snohomish river, congestion continues to worse because of regional job growth driving housing growth in Marysville/Arlington. If there were stricter land use rules prohibiting housing growth north of I5, there would be less congestion. Strict land use rules & a freeway expansion should also reduce congestion – given the absence of alterative N/S routes and high existing mode share, there is little latent demand to induce.

Freeway expansions – both actual and expected – certainly drive development decisions, which is why a growing city cannot build itself out of congestion. In an urban environment with an abundance of alternative routes & modes, freeway remove can indeed make congestion dissipate. In a growing region, it is far more important to use land use to channel efficient use of scare transportation capacity rather. But those are key qualifiers – actual/expected growth and alterative routes & modes. For a region with little prospective for growth or a town or small city without the scale to provide high quality alternatives, I do think there is a role in right-sizing the road network to meet the existing demand.

In the Midwest I’ve seen many small towns effectively use freeway bypass routes to absorb growing regional/freight traffic and free up the local street grid for local trips. Because these towns are growing slowly or not at all, the new exurban freeway induces minimal local demand, avoiding the congestion trap documented in this video. If land use rules prohibit suburban development around the new freeway exits (typically this simply means allowing only agricultural uses), this balance can be sustained.

AJ M

Given financial constraints, I have little interest in investing in rural highway expansions here in Washington, but I think the role of land use needs to be better highlighted when urbanists make the argument against freeway expansion and for urban freeway removal. The interdependence of housing growth and congestion underpins another critical urbanist position that we should strive to add housing adjacent to job centers because we seek to minimize VMT.