U.S.+Interstate+Highways

[|On the Road] - There are enough roads in the U.S. to stretch from the earth to the moon 8 times.

History The [|Lincoln Highway] was one of the first in the country.

The [|oldest Interstate segments] actually predate the establishment of the Interstate system. Early examples include a portion of the Grand Central Parkway in Queens, New York, which was opened to traffic in July 1936 and later was incorporated into the Interstate System as I-278. The Pennsylvania Turnpike between Irwin (southeast of Pittsburgh) and Carlisle (west of Harrisburg) was officially opened in October 1940 and is now designated as I-76 and I-70. Other freeways and toll roads were incorporated into the System rather than build new competing Interstate routes.

Facts
 * There are almost 4 million miles of road in the United States.
 * The U.S. interstate system has a total length of over 46,000 miles.
 * The concrete used to construct the Interstate System alone could build a wall nine feet thick and 50 feet high around the world’s equator.

[|U.S. Interstate Highways] - Individual guides include facts, mileage statistics, history, planned improvements, photographs, and basic information.
 * All overpasses must have a 16.5-foot vertical clearance above the freeway, although 14-foot overpasses may be permissible within urban areas.
 * Maximum grade is six percent, with certain exceptions allowed in mountainous regions.
 * numbering - Major Interstate routes are designated by one- or two-digit numbers. Routes with odd numbers run north and south, while even numbered run east and west. For north-south routes, the lowest numbers begin in the west, while the lowest numbered east-west routes are in the south. By this method, Interstate Route 5 (I-5) runs north-south along the west coast, while I-10 lies east-west along the southern border.


 * What's the problem?**

[|Interstate Design Standards] - The Federal-Aid Highway Act of 1956 called for uniform geometric and construction standards for the Interstate System. Examples of design standards for the Interstate System include full control of access, design speeds of 50 to 70 miles per hour (depending on type of terrain), a minimum of two travel lanes in each direction, 12-foot lane widths, 10-foot right paved shoulder, and 4-foot left paved shoulder. Initially, the design had to be adequate to meet the traffic volumes expected in 1975.


 * **Ask** - When design a highway system that is expected to be used for 30 years or more, how much traffic will there be using the roads? How fast will they go? How long will drivers be able to go between stops?
 * **Imagine** - To cover all the U.S. with high speed roads, the planners needed to come up with a strategy to arrange the roads to accommodate traffic evenly. They decided to divide the country up by population - roughly in tenths both east-west and north-south. That way there should be an Interstate highway near everyone where ever they were going from or to.
 * **Design, Build** - By coming up with design standards, all the roads would be similar. For safe traveling, the roads were wide and straight or gently curving. In some places, roads had to be located so they were not too steep for trucks with heavy loads.
 * **Improve** - New materials are developed to make roads safer. Grooving helps water to run off so the surface isn't slippery when it rains. The paint for the lane markings has been improved so it doesn't wear off and it reflects light at night, helping drivers stay on the roadway.


 * That's engineering**
 * [|concrete] - A composite material which consists of a binding medium, with embedded particles or fragments of a relative inert filler. In portland cement concrete, the binder is a mixture of portland cement and water; the filler may be any of a wide variety of natural or artificial, fine and coarse aggregates; and in some instances, an admixture.

> design speed, traffic volume, concrete, paint, reflective, adhesion, binding, medium, intert, filler, fine, coarse, aggregate
 * Engineering ideas**

Challenges for you to work on...
 * Do It**
 * plan a trip across the U.S. to some place you would like to visit at least 1,000 miles from home. Use [|Google Maps] to help plan the trip. Determine the route you would take if you traveled on Interstate Highways most of the way. Are there other routes that you could take to get to the same place? Which route would be farther? Why?


 * News, updates**


 * Learn more...**
 * [|Interstate System] - Dwight D. Eisenhower National System of Interstate and Defense Highways
 * [|Interstate Trivia] -

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