In case you aren't aware, "sister cities" and "town twinning" is a program by which two cities agree to form a friendly relationship and exchange people, ideas, gifts, and other things. These relationships can be chosen based on shared characteristics, like population, industries, ethnic communities, histories, and cultures.
These kinds of relationships could easily be applied to highways, and can even overlap with their twin cities. It would be fun to assemble a few pairings from the collective knowledge of the forum, though I would caution that pairing freeways together because they happen to use the same layouts or interchange types would be too boring.
To get us started:
Washington State Route 526 and
California State Route 14: Both highways pass through areas with close ties to the aviation and aerospace industry, and have appropriate names. WA 526 (the Boeing Freeway) runs through the main Boeing widebody factory that has long produced 747s, 767s, 777s, and (most) 787s. CA 14 is named the Aerospace Highway and travels close to Palmdale's aviation complex (which includes Boeing, NASA, and Northrop Grumman) and the National Test Pilot School. It also runs near the Mojave Air and Space Port, which is home to a massive
plane graveyard that typically includes more than a few planes produced in Everett.
Another industry-related one:
Washington State Route 520 and
California State Route 82. Both highways traverse some of the most tech-heavy corridors in the United States, and perhaps the world. WA 520 connects Amazon HQ1 to Microsoft's headquarters and the offices of Nintendo of America, among others, in Redmond. CA 82 runs through most of Silicon Valley and passes near many of the famous suburban campuses for tech giants like Google, Apple, and Facebook.
