Interstate 70 in Colorado
Interstate 70 is a transcontinental Interstate Highway in the United States, stretching from Cove Fort, Utah, to Baltimore, Maryland. In Colorado, the highway traverses an east–west route across the center of the state. In western Colorado, the highway connects the metropolitan areas of Grand Junction and Denver via a route through the Rocky Mountains. In eastern Colorado, the highway crosses the Great Plains, connecting Denver with metropolitan areas in Kansas and Missouri. Bicycles and other non-motorized vehicles, normally prohibited on Interstate Highways, are allowed on those stretches of I-70 in the Rockies where no other through route exists.
The United States Department of Transportation lists the construction of I-70 among the engineering marvels undertaken in the Interstate Highway System and cites four major accomplishments: the section through the Dakota Hogback, Eisenhower Tunnel, Vail Pass, and Glenwood Canyon. The Eisenhower Tunnel, with a maximum elevation of and length of, is the longest mountain tunnel and highest point along the Interstate Highway System. The portion through Glenwood Canyon was completed on October 14, 1992. This was one of the final pieces of the Interstate Highway System to open to traffic and is one of the most expensive rural highways per mile built in the country. The Colorado Department of Transportation earned the 1993 Outstanding Civil Engineering Achievement Award from the American Society of Civil Engineers for the completion of I-70 through the canyon.
When the Interstate Highway System was in the planning stages, the western terminus of I-70 was proposed to be at Denver. The portion west of Denver was included in the plans after lobbying by Governor Edwin C. Johnson, for whom one of the tunnels along I-70 is named. East of Idaho Springs, I-70 was built along the corridor of U.S. Highway 40, one of the original transcontinental U.S. Highways. West of Idaho Springs, I-70 was built along the route of US 6, which was extended into Colorado during the 1930s.
Route description
Colorado River
I-70 enters Colorado from Utah, concurrent with US 6 and US 50, on a plateau between the north rim of Ruby Canyon of the Colorado River and the south rim of the Book Cliffs. The plateau ends just past the state line and the highway descends into the Grand Valley, formed by the Colorado River and its tributaries. The Grand Valley is home to several towns and small cities that form the Grand Junction Metropolitan Statistical Area, the largest conurbation in the area regionally known as the Western Slope. The highway directly serves the communities of Fruita, Grand Junction, and Palisade. Grand Junction is the largest city between Denver and Salt Lake City and serves as the economic hub of the area. The freeway passes to the north of downtown, while US 6 and US 50 retain their original routes through downtown. US 6 rejoins I-70 east of Grand Junction; US 50 departs on a course toward Pueblo.I-70 exits the valley through De Beque Canyon, a path carved by the Colorado River that separates the Book Cliffs from Battlement Mesa. The river and its tributaries provide the course for the ascent up the Rocky Mountains. In the canyon, I-70 enters the Beavertail Mountain Tunnel, the first of several tunnels built to route the freeway across the Rockies. This tunnel design features a curved side wall, unusual for tunnels in the United States, where most tunnels feature a curved roof and flat side walls. Engineers borrowed a European design to give the tunnel added strength. After the canyon winds past the Book Cliffs, the highway follows the Colorado River through a valley containing the communities of Parachute and Rifle.
Glenwood Canyon
East of the city of Glenwood Springs, the highway enters Glenwood Canyon. Both the federal and state departments of transportation have praised the engineering achievement required to build the freeway through the narrow gorge while preserving the natural beauty of the canyon. A section of roadway features the No Name Tunnel, Hanging Lake Tunnel, Reverse Curve Tunnel, 40 bridges and viaducts, and miles of retaining walls. Through a significant portion of the canyon, the eastbound lanes extend cantilevered over the Colorado River and the westbound lanes are suspended on a viaduct several feet above the canyon floor. Along this run, the freeway hugs the north bank of the Colorado River, while the Central Corridor of the Union Pacific Railroad occupies the south bank.File:Hanging Lake Tunnel I-70 Glenwood Canyon.jpg|left|thumb|alt=A pair of bridges leading to a pair of tunnels at the canyon wall|The western portal of the Hanging Lake Tunnel; at this point in the canyon both the river and the railroad are directly below the freeway viaducts.
To minimize the hazards along this portion, a command center staffed with emergency response vehicles and tow trucks on standby monitors cameras along the tunnels and viaducts in the canyon. Traffic signals have been placed at strategic locations to stop traffic in the event of an accident, and variable message signs equipped with radar guns will automatically warn motorists exceeding the design speed of one of the curves.
Rocky Mountains
The highway departs the Colorado River near Dotsero, the name given to the railroad separation for the two primary mountain crossings, the original via Tennessee Pass/Royal Gorge and the newer and shorter Moffat Tunnel route. I-70 uses a separate route between the two rail corridors. From this junction, I-70 follows the Eagle River toward Vail Pass, at an elevation of. In this canyon, I-70 reaches the western terminus of US 24, which meanders through the Rockies before rejoining I-70. US 24 is known as the Highway of the Fourteeners, from the concentration of mountains exceeding along the highway corridor. Along the ascent, I-70 serves the ski resort town of Vail and the ski areas of Beaver Creek Resort, Vail Ski Resort, and Copper Mountain.The construction of the freeway over Vail Pass is also listed as an engineering marvel. One of the challenges of this portion is the management of the wildlife that roams this area. Several parts of the approach to the pass feature large fences that prevent wildlife from crossing the freeway and direct the animals to one of several underpasses. At least one underpass is located along a natural migratory path and has been landscaped to encourage deer to cross.
The highway descends to Dillon Reservoir, near the town of Frisco, and begins one final ascent to the Eisenhower Tunnel, where the freeway crosses the Continental Divide. At the time of dedication, this tunnel was the highest vehicular tunnel in the world, at., the facility was still the highest vehicular tunnel in the US. The Eisenhower Tunnel is noted as both the longest mountain tunnel and the highest point on the Interstate Highway System. The tunnel has a command center, staffed with 52 full-time employees, to monitor traffic, remove stranded vehicles, and maintain generators to keep the tunnel's lighting and ventilation systems running in the event of a power failure. Signals are placed at each entrance and at various points inside the tunnel to close lanes or stop traffic in an emergency. There are several active and former ski resorts in the vicinity of the tunnel, including Breckenridge Ski Resort, Keystone Resort, Arapahoe Basin, Loveland Ski Area, Berthoud Pass Ski Area, and Winter Park Resort.
Clear Creek
The freeway follows Clear Creek down the eastern side of the Rockies, passing through the Veterans Memorial Tunnels near Idaho Springs. Farther to the east, I-70 departs the US 6 corridor, which continues to follow Clear Creek through a narrow, curving gorge. The Interstate, however, follows the corridor of US 40 out of the canyon. The highway crests a small mountain near Genesee Park to descend into Mount Vernon Canyon to exit the Rocky Mountains. This portion features grade-warning signs with unusual messages, such as "Trucks: Don't be fooled", "Truckers, you are not down yet", and "Are your brakes adjusted and cool?". Runaway truck ramps are a prominent feature along this portion of I-70, with a total of seven used along the descent of either side the Continental Divide to stop trucks with failed brakes.File:TrucksDontBeFooled.JPG|thumb|left|alt=A highway near the top of a ridge. On either side of the highway are big yellow signs reading, "Trucks, Don't be Fooled—4 more miles of steep grades and sharp curves".|Warning sign stating, "Trucks, Don't be Fooled—4 more miles of steep grades and sharp curves"
The last geographic feature of the Rocky Mountains traversed before the highway reaches the Great Plains is the Dakota Hogback. The path through the hogback features a massive cut that exposes various layers of rock millions of years old. The site includes a nature study area for visitors.
Great Plains
As the freeway passes from the Rocky Mountains to the Great Plains, I-70 enters the Denver metropolitan area, part of a larger urban area called the Front Range Urban Corridor. The freeway arcs around the northern edge of the LoDo district, the common name of the lower downtown area of Denver. Through the downtown area, US 40 is routed along Colfax Avenue, which served as the primary east–west artery through the Denver area before the construction of I-70. Through downtown, US 6 is routed along 6th Avenue before departing the I-70 corridor to join I-76 on a northeast course toward Nebraska. The freeway meets I-25 in an interchange frequently called the Mousetrap. From I-25 on to I-225, I-70 serves—together with those two Interstates—as part of an inner beltway around Denver.I-70 has one official branch in Colorado, I-270, which connects the Interstate with the Denver–Boulder Turnpike. Where these two freeways merge is the busiest portion of I-70 in the state, with an average of 183,000 vehicles per day as of 2009. While State Highway 470 and E-470 are not officially branches of I-70, they are remnants of plans for an I-470 outer beltway around Denver that were canceled when the allocated funds were spent elsewhere.
Leaving Denver, the highway serves the redevelopment areas on the former site of Stapleton International Airport; runway 17R/35L crossed over the Interstate at the runway's midsection. East of Aurora, I-70 rejoins the alignment of US 40 at Colfax Avenue. The freeway proceeds east across the Great Plains, briefly dipping south to serve the city of Limon, which bills itself as Hub City because of the many rail and road arteries that intersect there. I-70 enters Kansas near Burlington, a small community known for having one of the oldest carousels in the United States.