I-5 Study Shows Benefits of Capping Urban Freeways

Putting a lid on the interstate through downtown Seattle could create new space for parks and housing, reduce pollution, and reconnect the disrupted street grid.

1 minute read

February 8, 2021, 8:00 AM PST

By Diana Ionescu @aworkoffiction


Freeway park over I-5

Freeway Park has spanned the I-5 in another part of downtown Seattle since 1976. | Scott Bonjukian / Freeway park over I-5

Doug Trumm reports on Seattle's "quiet" release of the Lid I-5 Feasibility Study, which highlights the benefits of capping freeways in cities. The report, funded through a community benefits package from the Washington State Convention Center expansion project, was "designed to understand the technical and financial feasibility of lidding the freeway and to look at opportunities for maximizing public benefits."

Trumm assesses the top takeaways from the study, which analyzed the potential impacts and effects of putting a "lid" on a 17-acre area of Interstate 5. According to the study, the lid could accommodate a 2.5-9.8 acre park, reconnect the street grid, reduce noise pollution, and improve stormwater drainage. The project would also create more space for housing construction in Seattle's dense downtown. "WSP did some structural engineering analysis to determine how much development could go atop the lid, and, while each section is different, the short answer is a lot. Bicknell’s 2019 article on earlier lid feasibility research had hinted midrise and some highrise development was possible. The final report estimated up to 4.7 million square feet of new housing is feasible–enough space for 4,500 homes–and between two and five million square feet of commercial/office space."

Lid I-5 Seattle's Scott Bonjukian told The Urbanist that "getting some more money for studies and planning in the next state transportation package is the next major goal."

Friday, January 29, 2021 in The Urbanist

Aerial view of Eugene, Oregon at dusk with mountains in background.

Eugene Ends Parking Minimums

In a move that complies with a state law aimed at reducing transportation emissions, Eugene amended its parking rules to eliminate minimum requirements and set maximum parking lot sizes.

December 3, 2023 - NBC 16

Green Paris Texas city limit sign with population.

How Paris, Texas Became a ‘Unicorn’ for Rural Transit

A robust coalition of advocates in the town of 25,000 brought together the funding and resources to launch a popular bus service that some residents see as a mobility lifeline—and a social club.

November 30, 2023 - Texas Monthly

Diagram of visibility at urban intersection.

How ‘Daylighting’ Intersections Can Save Lives

Eliminating visual obstructions can make intersections safer for all users.

November 27, 2023 - Strong Towns

Rendering of white, yellow, and purple Brightline West high-speed rail train speeding along highway median with blurred cars in foreground.

Brightline West Awarded $3 Billion in Federal Funding

The high-speed rail line will cut travel time between Southern California and Las Vegas roughly in half.

28 minutes ago - Fox 5

Rapid bus at station at night in Oklahoma City, Oklahoma.

OKC Celebrates New Rapid Bus Line With Free Rides

The agency wants to showcase the benefits of a recently opened BRT line connecting the northwest part of the city to downtown.

1 hour ago - The Oklahoman

Milky Way in Big Bend National Park, Texas.

Turning Out the Lights on Light Pollution

Limiting light pollution can have beneficial effects for humans, animals, and the local economy.

2 hours ago - Smart Cities Dive

Senior Planner

City of Kissimmee - Development Services

Planner II

City of Kissimmee - Development Services

Senior Travel Demand Modeler

Alamo Area Metropolitan Planning Organization

News from HUD User

HUD's Office of Policy Development and Research

New Updates on PD&R Edge

HUD's Office of Policy Development and Research

"Rethinking Commuter Rail" podcast & Intercity Bus E-News

Chaddick Institute at DePaul University

Urban Design for Planners 1: Software Tools

This six-course series explores essential urban design concepts using open source software and equips planners with the tools they need to participate fully in the urban design process.

Planning for Universal Design

Learn the tools for implementing Universal Design in planning regulations.