Purpose & Need

What is the background of the project?

The Westbound (WB) I-70 Peak Period Shoulder Lane (PPSL) project was initiated to respond to peak hour traffic congestion that occurs in the westbound direction in a manner similar to the improvements made in the eastbound direction, which opened to traffic late in 2015. The WB PPSL project is included in the January 2014 Memorandum of Understanding signed by CDOT, Clear Creek County, and Idaho Springs. It is consistent with the non-infrastructure components (expanded use of existing transportation infrastructure) of the 2011 Record of Decision.  It is an interim solution, not intended to address traffic problems twenty years in the future.

The project also includes Phase 2 of the County Road (CR) 314 (Frontage Road) project (Figure 1). Phase 2 of the Frontage Road project is included in the 2011 Record of Decision as are portions of the Greenway from Veterans Memorial Tunnels to Exit 241.

The WB PPSL project connects the eastern logical terminus of the Veterans Memorial Tunnels, because of the slower speeds that occur just west of that point and the western logical terminus of Empire Junction because of the high percentage of traffic that departs on US 40. It has independent utility and is a reasonable interim expenditure because it addresses the purposes of safety, reliability and congestion related to geometry and grade. It addresses these purposes until an ultimate solution can be identified in the study area.

What is the purpose for and the need of the project?

The purpose of the I-70 improvements is to provide westbound operational mobility improvements during peak periods when westbound traffic volumes are highest. Traffic congestion during peak periods erodes travel time reliability, increases traffic on local roads, decreases motorist safety, and compromises the ability of emergency responders to respond quickly.

Peak periods on westbound I-70 in the study area occur on Friday afternoons and weekend or holiday mornings, when Denver metropolitan area residents travel to the Colorado mountains for recreational purposes.

The purpose of the CR 314 improvements is to provide enhanced safety and mobility for vehicles, pedestrians and bicyclists between eastern Idaho Springs (Exit 241) and the improved CR 314 section just east of the recently completed Veterans Memorial Tunnels expansion.

Operational improvements on I-70 are intended to be implemented quickly, without substantial construction outside of the existing I-70 highway footprint. The proposed project is an interim solution for the study area in advance of longer-term major improvements to the I-70 Mountain Corridor in this area.

The definition of interim as used for the WB PPSL project is a solution that does not address all future 20-year needs but is consistent with the 2011 Record of Decision, minimizes throw away features, and addresses some elements of the transportation purpose and need as described in the Programmatic EIS.

Project Needs

The interim project is needed because of rapid population growth in the Denver metropolitan area. In 2010 the population was 2,798,000 residents. By 2015 the metropolitan area population had increased to 3,076,000, a 10 percent increase—almost 300,000 people—in 5 years[1].

The existing section of westbound I-70 from the Veterans Memorial Tunnels to US 40 at Empire Junction consists of two westbound travel lanes. The outside shoulder in the westbound direction is approximately 10 feet wide and the inside shoulder is approximately 4 feet wide. This stretch of I-70 is one of the most congested stretches of interstate in the entire I-70 Mountain Corridor. There are no pragmatic alternative routes between the Denver metropolitan area and the central mountains of Colorado. High traffic volume on I-70 during both the summer and the winter has led to ever increasing periods of slow traffic, which at times is considered a gridlock situation. The predominant period for westbound I-70 congestion is on Friday afternoons and Saturday mornings, from the Denver metropolitan area towards the mountains.

There is precedent in the study area for non-infrastructure improvements. In 2015 the Eastbound Peak Period Shoulder Lane (EB PPSL) opened on I-70 between Empire Junction and the Veterans Memorial Tunnels. The eastbound cross-section was reconfigured to provide a tolled travel lane on the inside shoulder during peak period demand of heavy traffic returning to the metropolitan area. This operational interim improvement project has notably alleviated eastbound congestion, reducing travel times by 21 minutes.

The westbound direction of I-70 has the following specific transportation needs

          • Travel Time Reliability. I-70 recreational travelers, transportation dependent commerce, and other I-70 users are severely affected by the slow and unpredictable travel times on this stretch of I‑70. This travel time reliability issue affects tourism and economic development.
            • During non-peak periods, in uncongested free-flow conditions, from the Veterans Memorial Tunnels to Empire Junction, travel time is 12 minutes. In contrast, travel time during peak periods ranges from 16 minutes to 21 minutes, increases of 33 percent to 75 percent. As Figure 2 shows, travel time during the peak period for 2035 is forecast to be just over 22 minutes.

              Congestion persists on the I-70 Mountain Corridor outside of the study area. The study area is a reasonable and suitable segment of I-70 for interim operational improvements as previously discussed.

              Figure 2: 2035 Peak Period Travel time

            • Local Access. Some motorists divert to alternate routes (primarily frontage roads), causing congestion for local traffic and reduced safety on these roads. The frontage road is the “main street” for Downieville, Lawson, and Dumont, and the only continuous east-west local street in Idaho Springs.
              • Weekday two-way traffic counts on the Stanley Road frontage road average 900 vehicles per day, but the volume more than doubles on weekend days. When I-70 travelers use the frontage road to avoid congestion on the highway, area residents and businesses are inconvenienced because they cannot get out of their driveways onto the frontage road. In addition, in-town roads in Idaho Springs are congested because travelers cut through town to avoid I-70 congestion.

              • Safety. Congestion-related crashes occur on I-70. Analysis of crash data in this stretch of I‑70 shows that there is a cluster of concrete barrier crashes in the westbound direction in two locations (around Exit 240 and just east of Exit 241), a cluster of rear-end crashes in the vicinity of the Veterans Memorial Tunnels, and a high concentration of wildlife-vehicle collisions along the US 40 off- and on-ramps (FHU 2017; Figure 3).
                • Emergency service providers responding to incidents in the study area are delayed by the congestion and lack of alternate ways to get to incidents on I-70. The current edge-to-edge pavement is narrow and emergency vehicles have difficulty maneuvering through the density of congested vehicles to access incidents during peak periods. The severe congestion affects speed of response to incidents on I-70, incidents in adjacent communities and incidents affecting recreationists using the Clear Creek corridor. The resulting delay in effective incident management compromises safety and substantially inconveniences other travelers.

                  Safety of I-70 travelers is also compromised by rocks falling onto the I-70 travel lanes, because of the highway’s close adjacency to steep mountain slopes. More information about rock fall issues is included below.

                  Figure 3. Congestion-Related Crashes on I-70 

                • TransitThere is a lack of safe and efficient facilities for serving regional transit passengers on the Bustang route, which serves the I-70 Mountain Corridor between Glenwood Springs and the Denver metropolitan area. This is also an issue with the County run Prospector bus. Passengers have a high exposure factor at the current stops in Idaho Springs on Miner Street, and no amenities to passengers are provided. Further, both eastbound and westbound buses must make inefficient turnarounds to return to I-70, causing increased travel time to all regional passengers.
                • Deficient Infrastructure. The current highway facility is deficient in many aspects, including substandard and failing facilities for drainage, guardrails, and pavement.
                  • Current levels of traffic far exceed original plans, as the highway facility in this area was designed in the 1950s. Some ramps have inadequate sight distance and deficient design of  acceleration and deceleration lanes.

                  • Emergency Evacuation. The frontage road (CR 314 or Stanley Road) which parallels I-70 throughout most of the corridor, is not built to standards and not paved the entire way. The frontage road serves an important role as a secondary evacuation route in case I-70 is closed due to flooding or rock fall, or in case a major emergency requires more lanes to move people quickly. The frontage road just east of Idaho Springs is one segment that needs to be improved to serve as a mechanism for emergency evacuation.
                  • Rock Fall Hazards. Westbound motorists are adjacent to unstable rock in the part of the study area west of Idaho Springs. This issue affects safety and mobility. Between 2014 and 2017 (as of October 2017) there have been 49 rock falls that have affected the entire interstate, WB I-70 lanes or shoulders. (Note: This will be updated after information is received for the entire year.) These events closed the travel lanes for a range of 30 minutes to several days. Appendix A of this document includes more data on these events.

                    The above described elements of project need form the framework for the development of a proposed action which will be assessed in the WB PPSL NEPA documentation, planned to be a Categorical Exclusion.


          2017. FHU. Safety Assessment Report

          Contact Us

          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.


          Colorado: The Official State Web Portal