Highway vs. Interstate: What’s the Difference?

In the United States, “highway” is a broad term for major public roads of many types, while an “interstate” is a specific subset: limited-access freeways built to federal standards as part of the Interstate Highway System. In short, every interstate is a highway, but not every highway is an interstate. This distinction shapes how roads are built, funded, signed, and experienced by drivers.

What Each Term Means

“Highway” describes any significant public road, from U.S. Routes and state highways to county arterials; it can refer to anything from a multi-lane urban boulevard with traffic lights to a rural two-lane route. “Interstate” refers specifically to the network of numbered routes (I‑5, I‑95, I‑80, etc.) created under the Federal-Aid Highway Act of 1956, designed primarily for high-speed, long-distance travel with controlled access and standardized engineering.

Outside the U.S., the words differ

Beyond the U.S., “interstate” isn’t used. Countries employ terms like “motorway” (UK), “autobahn” (Germany), “autoroute” (France), and “freeway” or “motorway” (Canada, Australia, New Zealand). These networks often mirror interstate-style design but follow national standards and naming conventions.

Who Builds, Pays For, and Oversees Them

Interstates are part of the National Highway System and are largely funded through the federal-aid program with state matches, though states own, operate, and maintain them day to day. Non-interstate highways can be federal-aid eligible (like many U.S. Routes and state highways) or funded entirely by states and localities. Federal oversight imposes stricter performance and design requirements on interstates, but states set speed limits and enforce operations.

Design and Access Standards

Interstates are engineered to facilitate safe, high-speed travel and efficient freight movement. The following features typically distinguish interstates from other highways:

• Controlled access: No at-grade intersections or driveways; entry/exit via ramps only.
• Grade separation: Overpasses/underpasses at crossings to eliminate cross traffic.
• Minimum design speeds/geometry: Curvature, grades, sight distances, and lane/shoulder widths meet AASHTO-based standards.
• Multiple lanes and medians: Usually at least two lanes each direction with a median or barrier.
• Uniform signage and markers: Distinct red-white-blue shields, exit numbering, and standardized guide signs.
• Limited non-motorized access: Pedestrians and bicycles are generally prohibited, though some rural western segments allow bicycles where no alternative exists.

Many non-interstate highways do not meet all these elements. Some are full freeways (often called expressways) that resemble interstates, while others have traffic lights, cross streets, and property access.

Numbering and Signage: How to Tell Them Apart

Route shields and numbering systems offer quick clues about a road’s type and function:

• Interstates: Red-white-blue shields; primary routes use one- or two-digit numbers (odd = north–south, even = east–west). Three-digit numbers denote auxiliary spurs and loops tied to a parent route (e.g., I‑405 off I‑5).
• U.S. Routes: Black-and-white shields; a separate historic network (e.g., U.S. 1, U.S. 66). May be freeways or conventional roads.
• State highways: State-specific shapes and numbering; standards and access control vary widely.
• Exit numbering: Interstates usually number exits by milepost; other highways may use sequential or mile-based systems depending on state policy.

These conventions help drivers anticipate the type of facility and level of access control they’re likely to encounter.

What Drivers Experience Day to Day

For travelers, the functional differences show up in predictable ways:

• Speeds and flow: Interstates support higher, more consistent speeds with fewer stops; non-interstate highways may slow for signals, driveways, and cross traffic.
• Safety: Controlled access reduces conflict points on interstates, generally lowering certain crash risks compared with at-grade highways.
• Tolls: Some interstates are tolled (e.g., parts of I‑95, I‑90); many highways are toll-free, but tolling depends on jurisdiction and facility.
• Freight and long-distance travel: Interstates are preferred for heavy trucks and cross-country routes due to geometry and reliability.
• Urban exceptions: Older urban interstates can have tight curves, short merge lanes, and left exits because they were built before today’s standards.

While not a guarantee of driving conditions, the interstate designation generally signals a faster, more access-controlled trip than the average highway.

Common Misconceptions

Several myths persist about highways and interstates; here are clarifications:

• “All freeways are interstates.” Not true. Many state or U.S. Routes are full freeways without interstate numbers.
• “Interstates are always toll-free.” Incorrect. Numerous segments, especially in the Northeast and Midwest, charge tolls.
• “Highway” means rural only. No—urban arterials and expressways are highways too.
• “Interstates are federally owned.” Generally false. States own and operate most segments, though they receive federal funds and oversight.

Understanding these nuances helps set realistic expectations about funding, design, and travel experience.

Concrete Examples

Real-world routes highlight how the labels play out:

• Interstate 95 vs. U.S. Route 1 along the East Coast: I‑95 is a mostly controlled-access freeway; U.S. 1 ranges from city streets to divided highways with signals.
• California State Route 99: A state highway with long freeway sections that are not part of the Interstate system, though some segments meet interstate-like standards.
• Massachusetts Turnpike (I‑90): An interstate that is also a tolled turnpike for much of its length.
• U.S. Route 101 in California: Mixes freeway and expressway segments; not an interstate despite major freeway portions.

These cases show that “interstate” signals a network and standard, while “highway” spans a broad spectrum of road types.

International Context

Globally, the U.S. “interstate” concept aligns with high-standard national networks like the Trans-Canada Highway (some freeway, some not), Europe’s E-road overlays across national motorways, the UK’s Motorway system, and Australia’s National Highway routes. Terminology and standards vary, but the principle of a core, limited-access network supporting trade and mobility is common.

Summary

A highway is any major public road; an interstate is a federally designated, limited-access highway built to consistent standards within the U.S. Interstate Highway System. Interstates typically feature controlled access, standardized design, and national numbering, while other highways range from freeways to signalized arterials. For drivers, the interstate label generally means faster, safer, and more predictable travel—though not necessarily toll-free—and it reflects a specific role in the nation’s transportation network.

What makes a road a highway?

A highway is a major public road primarily for connecting different towns and cities, characterized by features like multiple lanes, limited access points, and a focus on high-speed, long-distance travel. While it’s a broad term that includes high-speed, controlled-access roads like interstates and freeways, it can also refer to simpler, two-lane roads in rural areas, provided they are designated as a main public route for significant travel. Key distinguishing factors are its public nature, its purpose of connecting significant areas, and its typical design for heavier, faster traffic than local streets.
 
Key Characteristics

• Public Use and Maintenance: Highways are public roads, meaning they are open to the general public for travel and are maintained by a government entity. 
• Purpose: Their main purpose is to serve as a main route for travel and trade between towns, cities, and other significant locations. 
• Design:
  • Multiple Lanes: Highways typically have multiple lanes to accommodate heavier and faster traffic. 
  • Limited Access (for some highways): Some highways, like freeways and interstates, are fully controlled-access roads, allowing vehicles to enter and exit only at designated ramps. Other highways may have intersections and traffic lights. 
• Historical Context: The term “highway” originates from historical routes, often on higher ground, that connected major areas for travel and defense. 

Examples and Variations

• Highways vs. Freeways/Interstates: All freeways and interstates are considered highways, but not all highways are freeways. 
  • Freeway/Interstate: A fully controlled-access highway with no intersections, traffic lights, or direct access from properties. 
  • Expressway: A divided highway that is faster than a typical road but might have a higher level of access control than a freeway. 
• Varied Speeds and Flows: The term “highway” doesn’t guarantee a specific speed limit; it can encompass roads with various speed limits and traffic conditions. 

What makes a highway an interstate?

A highway becomes an Interstate when it meets federal standards for limited-access, divided highways and is part of the National System of Interstate and Defense Highways, established by the Federal-Aid Highway Act of 1956 and funded with federal money. Key characteristics include controlled access with ramps instead of intersections, a minimum of two lanes in each direction, 12-foot wide lanes, and inclusion in the national network designed for high-speed, cross-state travel and commerce.
 
Key Criteria for an Interstate

• Federal Standards: The highway must adhere to strict design standards set by the Federal Highway Administration (FHWA). 
• Limited Access: Vehicles can only enter and exit the highway via ramps or interchanges, with no traffic lights, stop signs, or at-grade intersections. 
• Divided Highway: It is a divided highway with a median to separate opposing traffic, ensuring safety and high-speed travel. 
• Lane Specifications: Interstates have a minimum of two travel lanes in each direction, with lane widths of at least 12 feet. 
• Design for High Speed: They are designed to accommodate high-speed traffic, often with speed limits from 50 to 70 mph or higher, depending on the terrain and area. 
• Part of the National Network: An Interstate Highway is not just any high-speed road but one designated by the American Association of State Highway and Transportation Officials (AASHTO) and approved by the FHWA. 

Historical Context

• President Dwight D. Eisenhower’s Vision: Opens in new tabThe Interstate System was conceived by President Eisenhower as a way to improve transportation and commerce, as well as for national defense purposes. 
• Federal Funding: Opens in new tabThe Federal-Aid Highway Act of 1956 provided the funding mechanism and authorization for building this nationwide network, with the federal government covering 90% of the construction costs. 

In Summary
While “highway” is a general term for a major road, “Interstate” refers to a specific, federally-regulated network of high-standard, controlled-access highways designed for efficient cross-state travel and commerce.

How do you know if a highway is interstate?

All the primary interstates are two-digit numbers less than one hundred. The north and south highways have odd numbers while the east and west highways have even numbers. The numbers start in the west and become larger, and the north and south roads increase as you travel north.

Are interstates better than highways?

According to DOT/NHTSA accident reports, highways tend to have more frequent but lower-speed accidents, like rear-end collisions or pedestrian-related crashes. Freeways see fewer accidents overall, but when they do happen, they’re often more serious due to high-speed travel and multiple-lane impacts.