How modern highways are built | By Interesting Engineering

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From the Autobahn in Germany to the sprawling U.S federal highway system, highways are some of the most important pieces of transportation infrastructure around the world. We often take them for granted but have you ever considered what sort of engineering goes into the construction of highways? Let's take a closer look!

The construction of any highway begins with the planning phase. Before laying the foundation, engineers and officials spend a lot of time determining the best route for traffic to flow through cities and across regions. Since highways last for so long they don't just consider the transportation problems of today but also think and plan out many decades into the future. After a plan for the highway is made, the next step is handing off the concept to a team of surveyors, architects, and engineers to complete the initial design. Surveying teams use GPS-based scanning tools to carefully map out the land where a highway will be built. The teams collect a massive amount of data including soil properties, drainage capabilities, future development potential, environmental effects, and even a complex digital point cloud that perfectly models the terrain. Once the data is collected, the design is finalized over what is usually a process of many years. The next step is construction. Since most highway systems are built by governments, choosing a company or companies to undertake the construction is usually done through a bidding process where different companies compete to offer the best price, quality, speed, and other factors. Like buildings and other structures, highways will need to hold a significant amount of weight throughout their lives which is why they need a very strong foundation. The phases of the construction process for highways usually looks like this:

1. Build up embankments and cut down hills to flatten out the terrain where the highway will be built.
2. Then, bulldozers and other heavy equipment will grade the soil and dirt, perfectly leveling out and smoothing the terrain together to create a subgrade.
3. Depending on the highway, engineers will often lay down different layers of soil. This soil is then heavily compacted to build up a strong sub-base grade to lay the roadway on top of.
4. While compacting soil down to its maximum density, engineers will lay down road drainage and storm sewer systems to ensure that the highways don't flood. After these preparatory and foundation laying steps are completed, the paving process can be started.

There are many different paving options for roadways but the main two highway choices are asphalt or a type of concrete. Asphalt uses a chemical compound known as bitumen, a byproduct of petroleum to essentially glue together crushed rock. This mixture is heated, laid, and then compacted to make the roadway surface. Concrete utilizes cement, water, and an aggregate like sand or rock. Concrete roadways are built by pouring the concrete into forms used to carefully shape and smooth the road surface. Asphalt is less durable compared to concrete but it's also far cheaper and faster to lay, especially for long stretches of road. Concrete, on the other hand, is highly durable but it's very expensive and time-consuming to use for constructing roadways. The choice will depend partly on cost considerations, environmental conditions, and what the roadway will be used for. After the paving process is completed, the roadway will undergo a period of testing. Engineers use seismology equipment to measure vibrations and fluctuations in the road surface. Engineers will also do load testing on the roadway making sure that the highway can support the necessary amount of weight. Finally, engineers have to check that the highway can support high water flow rates through its drainage system to help prevent accidents due to inclement weather.  After all of these construction and certification steps, the roadway can be opened up to the public for use. 

The process of constructing a highway usually takes many years. For example, plans for the Pan-American Highway which is made up of a series of interconnected roadways stretching across Canada, The United States, and 12 nations in South America began as far back as 1923. Construction on the first part of the roadway began in the 1940s. Today after almost 100 years of work, the road from the tip of North America to the tip of South America is still incomplete. The United States really loves highways too because not only does the U.S have the longest road network in the world but it is also home to the widest highway in the world. The Katy Freeway in Texas spans a monstrous 26 lanes across at its widest point and more than 219,000 vehicles drive across it every day. Highways are marvels of engineering indeed but they often go unremarked. Hopefully now as you're traveling across the highways of the world you'll appreciate the immense amount of engineering and planning that goes into them.

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✍ Vocabulary Review (find the word in the text that is suitable to each below description): 

1. a part of something
2. the basic systems and services, such as transport and power supplies, that a country or organization uses in order to work effectively
3. to not show that you are grateful for someone or something, and forget that you are lucky to have them
4. to pass or give something to someone
5. a principle or idea
6. of or at the beginning
7. very large in size, amount, or number
8. the system of water or waste liquids flowing away from somewhere into the ground or down pipes
9. an area of land, when considering its natural features
10. to try to be more successful than someone or something else
11. an artificial slope made of earth and/or stones
12. to become level or cause something to become level
13. a heavy vehicle with a large blade in front, used for pushing earth and stones away and for making areas of ground flat at the same time
14. An underground conduit for carrying off drainage water and waste matter.
15. done in order to get ready for something
16.  covering an area of ground with a hard, flat surface of pieces of stone, concrete, or bricks
17. a black, sticky substance, often mixed with small stones or sand, that forms a strong surface when it becomes hard
18. An incidental or secondary product made in the manufacture or synthesis of something else.
19. a dark, thick oil obtained from under the ground, from which various substances including petrol, paraffin, and diesel oil are produced
20. broken into small pieces by being pressed very hard
21. to press something together in a tight and solid way
22. to use something in an effective way
23. to experience something that is unpleasant or something that involves a change
24. the scientific study of the sudden, violent movements of the earth connected with earthquakes
25. a change, or the process of changing, especially continuously between one level or thing and another
26. (of the weather) unpleasantly cold or wet
27. with different parts or things connected or related to each other
28. Having the ugly or frightening appearance of a monster.
29. not noticed
30. extremely large in size or degree

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