The term 'MAJOR TRANSPORTATION ROUTE' can be summarized as an ARTERY, which is a six-letter word. An ARTERY is a large blood vessel that carries oxygenated blood away from the heart to the rest of the body. In transportation terms, an ARTERY is a major route or highway that connects two or more cities or regions. It is typically used for long-distance travel and is often the most efficient way to get from one place to another.