A highway is called a highway because the original ones were literally higher than the surrounding ground. The word traces back to ancient Roman roads, which were built with earth from side ditches piled toward the center, creating a raised mound for the road surface. This “high way” kept the path above standing water and mud, making it passable in all weather.
The Roman Origins of “High Way”
Roman engineers discovered early on that a road sitting at ground level turned into a swamp after every rain. Their solution was elegant: dig drainage ditches on both sides of the road and throw that excavated earth toward the center. The result was a crowned surface, higher in the middle than at the edges, that shed water naturally. This physical characteristic, a way that was literally high, gave us the word.
The term stuck because the design principle stuck. Centuries later, Scottish engineers Thomas Telford and John Loudon McAdam (whose name gave us “macadam” and eventually “tarmac”) are credited with building the first modern roads using the same core idea: raising the foundation in the center for water drainage. Their work in the late 1700s and early 1800s formalized what the Romans had figured out two thousand years earlier.
How “Highway” Separated From “Road” and “Street”
English has several words for paths you travel on, and each one carries a different origin story. “Road” comes from the Old English word “rád,” meaning “to ride,” and the Middle English “rode,” meaning a mounted journey. It originally described the act of traveling, not the surface itself. Over time it shifted to mean any route used by vehicles.
“Street” went the opposite direction. It comes from the Latin “strata,” meaning a paved surface, and originally applied to any constructed road. But by the Middle Ages, the only places with properly built roads were towns and cities. So “street” narrowed to mean an urban road, which is still how we use it today.
“Highway” kept its association with major routes connecting places. According to Britannica, the term historically referred to a major rural traveled way. In modern usage, it describes a road, rural or urban, where access points for traffic are limited and controlled. That functional definition is what separates a highway from an ordinary road: you can’t just pull onto it from any side street or driveway.
Highway, Freeway, and Expressway
These three terms sound interchangeable, but traffic engineers draw clear lines between them. The Federal Highway Administration defines them based on how tightly access is controlled:
- Freeway: A divided highway with full control of access. You can only enter and exit at designated ramps. No traffic lights, no intersections, no driveways.
- Expressway: A divided highway with partial control of access. Mostly ramp-based entry, but some at-grade intersections or traffic signals may exist.
- Conventional road: A street or highway without the access restrictions of a freeway or expressway.
“Highway” is the broadest of these terms. Every freeway is a highway, but not every highway is a freeway. A two-lane state route through farmland is a highway. So is a six-lane interstate. The word functions more like a category than a specific road type.
What “Highway” Means in U.S. Law
The legal definition is surprisingly expansive. Under federal law (Title 23 of the U.S. Code), “highway” includes not just the road surface but also rights-of-way, bridges, tunnels, railroad crossings, drainage structures, signs, guardrails, and protective structures connected to the road. Even portions of international bridges and tunnels count if a state transportation department covers the cost.
The most famous highways in the U.S., the Interstates, carry a formal name that reveals their original purpose: the Dwight D. Eisenhower National System of Interstate and Defense Highways. Congress named them that because their primary justification was national defense. The idea was that a connected network of high-speed roads would allow rapid military movement across the country, a concern rooted in Cold War strategy. The civilian convenience of driving cross-country was, officially at least, a secondary benefit.
Federal law also imposes strict rules on Interstate highways specifically. States cannot add access points beyond what the federal government originally approved without getting permission. Commercial establishments like gas stations cannot be built on Interstate rights-of-way. That’s why you exit the highway to get fuel rather than pulling into a service station in the median.
Why the Name Endured
Most modern highways aren’t noticeably raised above the surrounding landscape the way a Roman road was. Grading and drainage technology have advanced far beyond piling dirt in the middle. Yet the word survived because it had already shifted from describing a physical feature to describing a function: a major route for long-distance travel. By the time cars replaced horses, “highway” was already the standard term for the most important roads connecting towns and cities. The automobile age simply scaled it up.