October 2007

Media contact: Elisa Murray, elisa@sightline.org, 206-447-1880, x. 111

Author: Clark Williams Derry, clark@sightline.org.

Building new additional highway lanes increases total global warming emissions over the long term -- even if the project reduces congestion and emissions over the short term. Sightline's analysis has implications for transportation proposals such as the Columbia River Crossing between Oregon and Washington, and the Gateway Project in greater Vancouver, BC.

Complete analysis of the impact of new highway lanes on greenhouse gas emissions (pdf, 9 pages)

Sightline's blog post explaining the analysis


Brief summary

• Adding lanes to a highway will increase total global warming emissions over the long term -- even if it reduces congestion over the short term.
• Specifically -- we estimate that each extra lane-mile built will increase emissions of carbon-dioxide, the main greenhouse gas, by more than 100,000 tons over 50 years.
• Any short-term fuel savings from congestion relief are quickly overwhelmed by increased traffic volumes on the roadway.
• This estimate takes into account the potential for major increases in vehicle fuel efficiency over 50 years. Even assuming major mpg improvements, we still find that total emissions rise when congested highways are widened.
• However, if our region adopts a comprehensive, economy-wide cap on global warming emissions, concerns about the global-warming impacts of highway widening would be reduced.

More information:

Sightline's climate research project page