I-70 West Vail Pass Auxiliary Lanes

East Vail Noise Meeting held Feb. 13, 2020

Study Facts

  • What: Study improvements to I-70 on the west side of Vail Pass, including auxiliary lanes in both directions
  • Why: Make it safer to travel this steep terrain
  • Location: On the west side of Vail Pass on I-70, from mile points 180 to 190

CDOT is conducting an environmental assessment and conceptual design for safety improvements, including installing auxiliary lanes on the eastbound and westbound lanes on I-70 on the west side of Vail Pass. As part of this effort, existing and forecast traffic and safety issues will be determined, and long‐term solutions will be identified and evaluated as part of an environmental assessment. 

Once a preferred alternative is identified, design and construction can follow as funding becomes available.

Project elements include:

  • implementing the I‐70 Mountain Corridor Context Sensitive Solutions (CSS) process.
  • providing public and stakeholder involvement opportunities.
  • analyzing traffic and safety data and evaluating the impacts of proposed safety improvements.
  • collecting data and updating reports for potentially impacted environmental resources along the corridor.
  • conducting analysis to determine the most practical and least impactful solutions to add auxiliary lanes on West Vail Pass.
  • completing an environmental assessment (EA).


I-70 through Vail Pass serves as a major transportation route across Colorado's Rocky Mountains, providing a critical interstate link for the country. The steep grades, roadside terrain, and extreme weather events make I-70 over Vail Pass a challenging mountain pass to travel and maintain.

When originally constructed in the 1970s, Vail Pass was at the forefront of modern highway design. The existing roadway was purposely constructed to minimally impact the unique natural environment of Vail Pass.

I-70 PEIS & ROD: 2011
Improvements in this project study area were included as a part of the preferred alternative CDOT selected in the I-70 Mountain Corridor Programmatic Environmental Impact Statement (I-70 PEIS, a tier 1 National Environmental Policy Act (NEPA) process).

In 2011, FHWA signed a Record of Decision (ROD), which included a decision about capacity, mode and location for future transportation improvements. The PEIS recommended to add auxiliary lanes up and down the west side of Vail Pass from mile point 180 to mile point 190.

West Vail Pass Environmental Assessment: 2006/2007
An environmental assessment was initiated in 2006 to identify the transportation needs on West Vail Pass and evaluate alternatives to address the needs. The project was halted due to the ongoing PEIS study and a lack of funding.

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