Welcome to the fourth installment of CR4's celebration of the 50th anniversary of the Eisenhower Interstate Highway System. We began on Monday, with "A Giant Nationwide Engineering Project" and continued on Tuesday, with "Roots of the Roads", and Wednesday, "The Politics of Passage". Check back tomorrow for the "The Road Ahead" .

Fifty years ago today, President Dwight D. Eisenhower began to change the face of a nation with the stroke of a pen. From his bed at Walter Reed Army Medical Center, Eisenhower signed the Federal-Aid Highway Act of 1956, approving the construction of a National System of Interstate and Defense Highways. During the project's early years, Americans anticipated the arrival of safe new roads and good-paying construction jobs. By the mid-1960s, however, citizens became concerned about the demolition of historic neighborhoods and the decay of downtown centers. The 1970s brought higher gasoline prices, smaller cars, and a newfound concern for the environment. In 1973, Congress began spending highway funds on mass transit, bike paths, and walking trails. Still, some of the Eisenhower Interstate Highway System's greatest achievements lay just over the horizon.

Today, CR4 salutes the men and women who designed and built the beltways, bridges, tunnels, and stretches of lonely road that make up what one observer called our "great nationwide engineering project". Although the engineering accomplishments are many, some of the finest examples include: The Leonard P. Zakim Bunker Hill Bridge, I-93 (Boston, MA); The Leif Erickson Tunnel, I-35 (Duluth, MN), The Papago Freeway, I-10 (Phoenix, AZ); Glenwood Canyon, I-70 (Colorado); and last - but not least - The Capital Beltway, I-495 (Washington, DC).

The Leonard P. Zakim Bunker Hill Bridge, I-93 (Boston, MA)

The Leonard P. Zakim Bunker Hill Bridge is the widest cable-stayed bridge in the world and the first to use a hybrid frame of steel and concrete. Built at a cost of $100 million and completed in May 2002, the design is the work of Christian Menn, a Swiss-born architect and engineer. The bridge's signature features include two load-bearing towers which resemble the Bunker Hill Monument in nearby Charlestown, Massachusetts. The 116 cable stays which support the roadway form a fan that suggests a ship at sea. As with all sound design, form follows function. Today, the Leonard P. Zakim Bridge carries 10 lanes of traffic along I-93, the busy corridor which connects Boston to points north. Motorists who enter and exit Beantown pass through the legs of hollow, concrete towers which are connected to cable stays and supported by steel shafts driven into bedrock. Designed to weather winds of over 400 miles per hour, the bridge can also withstand a 7.9 magnitude earthquake.

Resources:
http://www.leonardpzakimbunkerhillbridge.org/
http://www.bostonroads.com/crossings/zakim/
http://www.massturnpike.com/bigdig/background/crb.html
http://www.pbs.org/wgbh/nova/bridge/meetcable.html

Leif Erickson Tunnel, I-35 (Duluth, MN)

The Leif Erickson Tunnel in Duluth, Minnesota completes a 1,500-mile stretch of interstate highway (I-35) that runs all the way to the Mexican border at Laredo, Texas. Built at a cost of $220 million and completed in October 1992, the 1,480-foot-long tunnel features a 580-foot-long ceramic tile wall that faces Lake Superior and decorates a walking trail with historic marine images. The use of cut-and-cover tunnels, extensive landscaping, noise abatement technologies, and architectural design treatments met the concerns of community activists who had opposed the extension of I-35 through downtown Duluth for over 30 years. Today, the Leif Erickson Tunnel is a source of local pride and part of Lake Place Park, a popular tourist destination. The highway's unique design connects the downtown with the lakefront, but limits speeds to 45 mph and prohibits trucks that weigh more than 9000 lbs.

Resources:
http://www.fhwa.dot.gov/byday/fhbd1028.htm
http://www.tfhrc.gov/pubrds/06jan/01.htm
http://www.cityofsacramento.org/econdev/msc/pdfs/Appendix%20B.pdf

The Papago Freeway, I-10 (Phoenix, AZ)

Completed in 1991, the Papago Freeway in Phoenix, Arizona combines engineering, landscaping, art and architecture. During the 1960s, plans for an I-10 corridor through the heart of the city called for a massive interchange and system of roadways rising 100 feet into the air. During the 1970s, public opposition mounted and citizens expressed their displeasure through ballot initiatives. The solution was to start over. In 1979, voters approved a plan which moved 13 acres of roadway underground so that a public park could be build above. Today, the Papago Freeway runs through the western part of Phoenix, leaving in tact some of the city's oldest and most historic neighborhoods. Recessed roadways are framed with sand-colored, soundproof walls that feature Native American patterns. An adjacent bike trail is landscaped with native, low-water plants.

Resources:
http://www.thenewi64.org/1c1_az.jsp
http://www.arizonaroads.com/urban/papago.html
http://americanhistory.si.edu/ONTHEMOVE/collection/object_672.html
http://americanhistory.si.edu/ONTHEMOVE/exhibition/exhibition_16_4.html

Glenwood Canyon, I-70 (Colorado)

Formed by the Colorado River, Glenwood Canyon is 16 miles long and surrounded by steep, rocky cliffs. In 1960, the federal government announced plans to extend I-70 from Denver to Utah. After studying several alternatives, the Colorado Department of Highways determined that a route through the canyon represented the path of least resistance. Major work began in April 1980 and at its height, the project employed more than 500 people a day. To address the concerns of environmentalists, road crews used balanced cantilever construction, a bridge-building technique that begins from above rather than below. Perched atop a bridge column, a gantry builds the bridge outward, using pre-cast segments that minimize the road's impact on the land. Although balanced cantilever construction had never been used in the United States, I-70 through Glenwood Canyon was completed a year ahead of schedule in 1992. The project's $490 billion price tag included miles of pre-cast and post-tensioned retaining walls - possibly the first of their kind - and miles of recreational trails.

Resources:
http://www.mesalek.com/colo/glenwood/history.html
http://www.uwsp.edu/geo/projects/geoweb/participants/dutch/VTrips/GlenwoodCanyon.HTM

The Capital Beltway, I-495 (Washington, DC)

The Capital Beltway is a 64-mile stretch of highway (I-495) that encircles Washington D.C. and suburbs such as Bethesda, Maryland and Arlington, Virginia. The first section opened on December 21, 1961 and included the Woodrow Wilson Memorial Bridge, a six-lane, double-leaf drawbridge that allows large, ocean-going vessels to access port facilities. The remainder of the $189 million highway was completed on August 17, 1964. Today, as many as 1 million vehicles a day travel the Beltway. Congestion around areas such as "The Mixing Bowl", a complex interchange near the Pentagon, challenges even experienced drives. Originally, engineers designed the road's Maryland section to carry 55,000 vehicles per day and Virginia's to carry 49,000. Both figures were exceeded by the end of 1965 – over 40 years ago.

Resources:
http://en.wikipedia.org/wiki/Capital_Beltway
http://www.washingtonpost.com/ac2/wp-dyn/A64110-2004Aug13?language=printer

Click here for our fifth and final installment, "The Eisenhower Interstate Highway System: The Road Ahead".