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The right design of the highways is a major aspect in building a civilized country because it provides safety, ease of traffic, ease of extension when it is needed. I will apply these to the design of interstates and highways in the U S.
First, in the United States interstates were designed for safe operation through a complete controlled access. The intersections are at different levels with access through exchange ramps, which avoid the movement conflict between different highways. Also, the highways are totally separated (isolated) from the residential areas with an exit leads to each city without having the highways itself run through it, which avoid the conflict between speed cars and walking people (individuals).
Second, the highway moved the traffic away from inside the city leaving a chance to only the local residents to deal with their own traffic. For example, in some country like Egypt, the highways run in some areas right straight through the local streets crossing and conflicting with them, and that cause a huge amount of traffic and accidents. In addition, in the U S, there are at least four lanes in all the interstate highways for easy and fast travel.
Finally, the highways designs provided the possibility of extension due to the increase of traffic loads via two talented elements:
1) Most of the highways have wide shoulders and empty spaces along them, which gives the opportunity of adding more lanes.
2) The highways are rarely conflicting with building, which makes it easier to widen the highways.