More Lanes Mean More Emissions

As Seattle considers a plan to spend more than $17 billion on road and transit projects, the Sightline Institute looks at how the city's greenhouse-gas emissions would increase if a new land of highway is built.

1 minute read

October 8, 2007, 10:00 AM PDT

By Nate Berg


"We recently took a look at the greenhouse gas implications of building a new lane-mile of highway in a congested urban area. Our conclusion is that every extra one-mile stretch of lane added to a congested highway will increase climate-warming CO2 emissions more than 100,000 tons over 50 years. Those emissions are broken out as follows:

* Road construction and maintenance: 3,500 tons
* Net congestion relief: -7,000 tons [that's negative, folks]
* Additional traffic on the roadway: 90,000 tons
* Additional traffic off the roadway: 30,000 - 100,000 tons
* TOTAL: 116,500 - 186,500 tons

The relationship between road building and CO2 emissions has relevance far beyond this year's RTID debate. British Columbia is considering a massive roadway expansion in greater Vancouver, called the Gateway Program, which includes a controversial twinning of the Port Mann Bridge. And major road widening proposals occasionally rear their heads throughout Cascadia and beyond."

"The most curious thing is that some supporters of this sort of road expansion try to claim the environmental high-ground: adding lanes to crowded highways, they claim, will relieve congestion, which will reduce overall emissions."

"Our analysis shows this claim is bunk."

Thursday, October 4, 2007 in Sightline Institute

stack of books

Planetizen’s Top Planning Books of 2023

The world is changing, and planning with it.

November 24, 2023 - Planetizen Team

Close-up of 'Red Line Subway Entry' sign with Braille below and train logo above text in Chicago, Illinois.

Chicago Red Line Extension Could Transform the South Side

The city’s transit agency is undertaking its biggest expansion ever to finally bring rail to the South Side.

November 24, 2023 - The Architect's Newspaper

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

People walking on paved path in green city park with trees and tall city skyscrapers in background.

Green Spaces Benefit Neighborhoods—When Residents can Reach Them

A study comparing green space and walkability scores found that, without effective access to local parks, residents of greener neighborhoods don’t reap the health benefits.

December 3 - American Heart Association News

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 - NBC 16

White, blue, and red Chicago transit bus at an urban bus station with shelter.

Chicago Announces ‘Better Streets for Buses’ Plan

The plan establishes a ‘toolkit’ of improvements to make the bus riding experience more reliable, comfortable, and accessible.

December 3 - City of Chicago

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.