Frequently Asked Questions


In June 2011, the U.S. Department of Transportation issued a Record of Decision (ROD) outlining a number of actions to address I-70 Mountain Corridor congestion and provide a path forward to improving mobility along the corridor. Similar to the Eastbound Peak-Period Shoulder Lane (PPSL) project that was implemented in 2015, the Westbound PPSL uses the existing shoulder lane as a tolled third travel lane only during peak travel times on 12 miles of westbound I-70 between the Veterans Memorial Tunnels and Empire Junction. The Westbound PPSL is not the "permanent" solution for the corridor and is categorized as an interim, operational improvement by the Federal Highway Administration (FHWA).

The peak periods on westbound I-70 are Friday afternoons, and Saturday and Sunday mornings during peak summer and winter travel seasons, as well as holiday mornings. Therefore, the Westbound PPSL is likely to be open to traffic Friday afternoon and in the mornings on Saturdays, Sundays, and weekday holidays. Exact hours of operation have not yet been determined.

Operations will be flexible and available for use beyond those days or times if traffic congestion conditions warrant, so long as the operating hours stay within the daily and annual guidelines established by a Memorandum of Understanding (MOU) signed by the CDOT and the Federal Highway Administration (FHWA).

Because the Eastbound and Westbound PPSLs are considered interim projects, the Federal Highway Administration (FHWA) and CDOT signed Memoranda of Understanding that define the maximum yearly times of operations. The agreement for the Eastbound PPSL is that it can be open no more than 20 percent of the days of the year, including holidays (i.e., 73 days) and no more than 7.5 percent of the annual hourly time (equivalent to 73 days x 9 hours per day). The agreement for the Westbound PPSL is anticipated to be similar.

Rather than widen the highway, the Eastbound PPSL uses existing infrastructure to address peak-period congestion in the interim until additional capacity can be added. Full-width shoulders and lanes were considered on the Eastbound PPSL but not implemented because of cost, environmental impacts, and inconsistency with the 2011 ROD, which did not identify this area as one to be widened for additional highway capacity until certain triggers are met. These triggers have not yet been met and can be found in the 2011 Record of Decision.

As an interim, operational improvement, the temporary nature of the project enables the use of less-than-ideal widths for lanes and shoulders. CDOT and the Federal Highway Administration (FHWA) are working through the I-70 Mountain Corridor Context Sensitive Solutions (CSS) process with local agencies and other stakeholders to determine the appropriate shoulder and lane widths for the Westbound PPSL project. FHWA determines if any variances to normal interstate standards are acceptable.

The accident history of the Eastbound PPSL is being examined, and this information will be used during the National Environmental Policy Act (NEPA) process for the Westbound PPSL project. Preliminary information is that accident severity has decreased compared to before the Eastbound PPSL was constructed.

CDOT is planning to construct a new bridge over Clear Creek from Stanley Road to Fall River Road, but it will not be a part of the Westbound PPSL project. The bridge project is planned to begin before construction of the Westbound PPSL project.

CDOT is aware of this sight distance issue at the top of the westbound off-ramp to CO 103. The issue will be addressed as a part of the Westbound PPSL project.

Safety of the existing infrastructure is a critical part of purpose and need development in the National Environmental Policy Act (NEPA) process, which is ongoing. This includes exit ramps, so if the exit at 232W is determined to be dangerous, it will be improved. CDOT maintenance crews quickly take care of knocked-down signs as they are notified of those problems.

Clear Creek Greenway

Four sections of the Clear Creek Greenway are planned to be funded by CDOT as a part of a separate project. These four sections include a portion in the Downieville-Lawson-Dumont area from the animal shelter east to a point just west of the Clear Creek County Wastewater Treatment Plant.

The alignment assumed for all Greenway sections is that adopted in 2006 and incorporated into the recent design work by Clear Creek County, the Clear Creek Greenway Authority, and Idaho Springs. This alignment includes a small section along the North Frontage Road to connect to Fall River Road and the new bridge.

In addition, a feasibility study is being conducted that examines placing the Clear Creek Greenway north of I-70 to avoid the Silver Lakes area. If you have further questions, please contact Amy Saxton with the Clear Creek Greenway Authority at 720-588-9443.


Except in limited circumstances (e.g., adverse weather, construction zones), per 23 CFR 658.11(d), the state of Colorado cannot deny truck access nor place restrictions on the interstate system without approval from the Federal Highway Administration (FHWA). The request needs to be based on safety concerns. It requires an analysis of the impact to interstate commerce, and analysis and recommendations of alternative routes.

Motor carriers groups are involved in the Westbound PPSL project. CDOT is working with these groups to consider impacts to truck traffic movements both during construction and after the Westbound PPSL is in operation.

CDOT is not considering tolling all lanes on I-70. There will be two free lanes just like there are now. However, if local residents choose to travel in the PPSL, they will have to pay a toll.

CDOT conducted some tests with traffic metering, and the benefits were not clear. This could be considered in the future if appropriate.

CDOT has upgraded its intelligent highway systems along I-70 to help better respond to these needs. These upgraded systems will better inform users of road conditions in the future. CDOT is continuing to develop improvements in traffic management and intelligent systems. During construction, there will be a robust public information plan to notify travelers of closures and detours.

Speed limits will be posted for the Westbound PPSL. Because the Colorado State Patrol is responsible for enforcing speed limits, CDOT will discuss with the CSP implementing more frequent enforcement of speed limits. Additional pull-outs for enforcement are being considered during the Westbound PPSL project development process.

Construction Impacts

One of CDOT's key concerns is to minimize impacts as much as possible to the traveling public. The recently completed Veterans Memorial Tunnels and Eastbound PPSL projects did disrupt traffic during construction, but there is no indication that travelers chose to never come back. Trying to minimize the disruption to travelers and communities during construction is one of the main goals of CDOT projects.

Ways to address potential air quality impacts during construction will be considered during the NEPA process.

Detours during construction will be considered during the NEPA process. One of CDOT's goals is to minimize short-term impacts to traffic as much as possible. The short-term effects to truck traffic and Henderson Mine operations will likely be similar to those experienced during the Eastbound PPSL project.

Dumont-Lawson-Downieville Noise Issue

The Westbound PPSL project is an interim project and does not meet the definition of the type of project that requires a noise analysis. Based on information collected after the Eastbound PPSL project, adding a part-time tolled lane does not perceptibly change noise levels. No new sound barriers are planned at this time.

Colorado state law now requires that any vehicle equipped with engine compression brake devices (commonly referred to as "Jake brakes") be equipped with proper mufflers. Failure to do so results in a $500 fine. Enforcement of this law is the responsibility of the local authorities.

CDOT has not restricted the use of these devices for safety reasons. However, CDOT has assisted local entities with this issue by installing "Engine Brake Mufflers Required" signs along selected highways, which could also be considered for this area.

The cross-section widths along the corridor included in the Downieville area are being studied as a part of the NEPA process. Rumble strips are a safety measure and being considered as part of the cross-section for the Westbound PPSL project.

Safety data from the Eastbound PPSL project is being reviewed to evaluate the effectiveness of rumble strips in improving safety. The noise impact of rumble strips is also being evaluated and consideration is being given to moving the strips to reduce noise.

Environmental/Socioeconomic Resources

The Westbound PPSL project development process includes consideration of wildlife. A specific committee called ALIVE is addressing wildlife needs and possible solutions.

Air quality will be considered as a part of the NEPA process. Decreasing traffic congestion with the PPSL can be expected to reduce air pollution from vehicles.

Water quality will be considered as part of the NEPA process. A specific committee called SWEEP is tasked with developing water quality-treatment plans. A Sediment Control Action Plan has also been prepared that defines treatment for excess sediment along I-70. Its recommendations will be considered in the NEPA process.

The frequency of CDOT Bustang service on I-70 between Glenwood Springs and Denver area has been recently increased, and it is likely to be further increased as needs grow, and if funding is available. CDOT is conducting outreach to providers of shared ride services as part of the NEPA process.

Aesthetics are an important part of any project that CDOT studies. All projects on the I-70 Mountain Corridor must comply with the Aesthetic Guidance that was developed specifically for the corridor.

The Westbound PPSL project is an operational improvement and will not be adding capacity to the interstate. However, land use will be a consideration in the NEPA process. CDOT does not make decisions about local land use, which include water supply considerations. In the Westbound PPSL project area, Clear Creek County and the City of Idaho Springs have authority over land use decisions.

If the railroad tie noise wall is impacted, it will be reconstructed, or another wall will be added in the same location.

If parking is impacted by the improvements to the CO 103 interchanges as part of the Westbound PPSL project, it will be mitigated. Right now, we don't anticipate removing any parking spaces, but the parking lot may be reconfigured. The city is also planning to build a parking garage in the future.

The Westbound PPSL project is anticipated to stay within CDOT's existing right of way; therefore, property will not be acquired, and no houses will be impacted.

One of the key factors in the NEPA process in Idaho Springs will be to minimize any new right-of-way needs. Right now, no new right of way in Idaho Springs is anticipated to be needed.


Some businesses in Idaho Springs have reported that business conditions improved after the Eastbound PPSL was constructed. Data on economics for existing conditions and future 2040 conditions will be developed during the NEPA process.

The findings relative to the benefit provided for the cost of improvements for the recently completed Eastbound PPSL is that it was very cost-effective (I-70 Eastbound Peak Period Shoulder Lane TIGER Application, CDOT April 2014.) The project substantially saved travel time and substantially improved time to clear crashes, at a cost that is much less than the cost to build a new lane.

CDOT completed an Advanced Guideway System (AGS) Feasibility Study in August 2014. An AGS was determined to be technically feasible but not financially feasible. The NEPA process currently underway for highway improvements does not preclude a future AGS, which could be implemented once funding for it is identified.

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Westbound Peak-Period Shoulder Lane Context Statement

The I-70 Mountain corridor is a magnificent, scenic place in close proximity to the Denver Metro area. Human elements are woven through breathtaking natural features. The integration of these diverse elements has occurred over the course of time. The corridor is a recreational destination for the world, a route for interstate and local commerce and a unique place to live.

I-70 is also federally designated as a high-priority corridor, a significant part of the defense network, a major east/west continental corridor and a major economic corridor for Colorado. For many local communities along the corridor, I-70 is the lifeline, primary access and only connection to other communities.

Current I-70 roadway geometry is constrained with narrow shoulders and tight curves that impact safety, mobility, accessibility, and capacity for travelers and residents. In a manner that respects the unique environmental, historic, community and recreational resources in Clear Creek County, westbound improvements are needed to lessen delays caused by peak period volumes.


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