Highway vs. Interstate: What’s the Difference?

An interstate is a specific kind of highway in the United States: a federally designated, access-controlled freeway that is part of the Interstate Highway System, while “highway” is a broader term for any major public road, including U.S. Routes, state routes, and local arterial roads. In practice, all interstates are highways, but not all highways are interstates, and they differ in purpose, design standards, numbering, and management.

Definitions at a glance

In everyday U.S. usage, “highway” can refer to almost any significant road—from rural two-lane routes with intersections to multi-lane freeways. “Interstate,” by contrast, refers specifically to roads in the Interstate Highway System (e.g., I-5, I-95), a nationwide network intended for long-distance travel, commerce, and defense, built to consistent standards for safety and speed.

Key differences in the United States

The following points outline how interstates differ from other highways in designation, design, and administration.

• Designation and network: Interstates carry an “I-” number and the red-white-blue shield; other highways may be U.S. Routes (US-), state routes (SR-), or county routes, each with different shields and numbering conventions.
• Access control: Interstates are controlled-access freeways with on/off ramps and no at-grade intersections on the mainline; many highways are not access-controlled and may have traffic lights, driveways, and cross streets.
• Design standards: Interstates follow stricter federal standards (wide lanes and shoulders, medians, gentler curves, grade-separated interchanges) to support higher, consistent speeds and heavy traffic volumes.
• Purpose and continuity: Interstates form a continuous national network optimized for long-distance travel and freight movement; many other highways primarily serve regional or local connectivity.
• Funding and oversight: States typically own and maintain interstates with significant federal funding and oversight via the Federal Highway Administration (FHWA); other highways may rely more on state or local funding with looser federal standards.
• Speed and restrictions: Interstates often have higher posted speed limits and typically prohibit pedestrians, bicycles, and low-speed vehicles; other highways may allow them depending on state law.
• Reliability and amenities: Interstates generally provide frequent services (rest areas, service plazas in some states) and uniform signage to aid navigation; amenities on other highways vary widely.

Taken together, these differences make interstates the default choice for fast, long-distance travel, while non-interstate highways fill in regional and local mobility needs.

Where they overlap

Despite their differences, interstates and other highways share important similarities that can blur distinctions for drivers.

• Both are public roads that carry a mix of passenger and commercial traffic.
• Both can be multilane and high-speed; many state or U.S. highways are built to full freeway standards.
• Both can include toll segments, depending on the state and facility.
• Both use standardized traffic control devices and signs per the Manual on Uniform Traffic Control Devices (MUTCD).

Because of this overlap, drivers may experience interstate-like conditions on non-interstate highways—and vice versa in rare legacy locations.

Special cases and exceptions

Toll roads and interstates

Interstates are often free to use, but not always. Some interstates run along toll facilities (for example, parts of I-90 on the Massachusetts Turnpike and portions of I-76/I-276 on the Pennsylvania Turnpike). Conversely, many non-interstate highways also charge tolls (e.g., New Jersey’s Garden State Parkway).

Noncontiguous and nonstandard interstates

Alaska, Hawaii, and Puerto Rico have federally designated “Interstate” routes that are not connected to the continental network and may not meet all mainland design standards, yet they receive federal interstate funding. A handful of legacy segments on the mainland have unusual features (notably the Breezewood, Pennsylvania connection on I-70) where traffic briefly uses surface streets to transition between limited-access roadways.

State and U.S. highways that are full freeways

Many non-interstate highways meet or exceed interstate-like standards, such as large stretches of US-101 in California, GA-400 near Atlanta, FL-826 in Miami, and CA-99 in the Central Valley. These operate like interstates but are designated and managed as U.S. or state routes.

Numbering and signage

Understanding the numbering and sign conventions helps distinguish interstates from other highways at a glance.

• Interstates: Two-digit interstates use even numbers for east-west routes (higher numbers in the north) and odd numbers for north-south routes (higher in the east). Three-digit interstates denote spurs/loops around cities; the last two digits reference the parent route.
• U.S. Highways: Numbering is broadly opposite (odd numbers increase west to east; even numbers increase north to south), reflecting an older national grid separate from interstates.
• State routes: Numbering varies by state policy; shields often feature state outlines or unique symbols.
• Shields: Interstates use a red-white-blue crest; U.S. Highways use a black-and-white shield; state routes have state-specific designs.

These patterns aren’t just cosmetic—they signal the road’s network role and can hint at expected design and connectivity.

Practical guidance for drivers

Here are some quick considerations when choosing between an interstate and another highway for a trip.

• For speed and predictability, favor interstates; they minimize stops and cross-traffic.
• For scenic routes or local access, non-interstate highways may offer better proximity to towns and attractions.
• Watch signage: interstate shields and exit numbers simplify navigation; surface highways may have frequent signals and driveways.
• Check for tolls and restrictions: some interstates and parkways have tolls or vehicle limits (e.g., parkways in NY often restrict trucks).
• Expect more frequent services on interstates, though rural stretches may still be sparse—plan fuel and rest stops accordingly.

Balancing time, cost, and experience will help you choose the right road for each trip.

Global terminology note

Outside the U.S., “highway” may simply mean a major road and does not imply full access control. Equivalent terms for controlled-access highways include “motorway” (UK, Ireland), “autobahn” (Germany), “autoroute” (France), and “autostrada” (Italy). “Interstate” is a U.S.-specific designation.

Summary

All interstates are highways, but not all highways are interstates. Interstates are part of a federally designated, access-controlled network engineered for fast, long-distance travel and freight. Other highways—U.S., state, and local routes—range from two-lane roads with intersections to full freeways that can look and feel like interstates. Understanding the differences in designation, design, and numbering helps drivers set expectations for speed, access, and navigation.

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.

Are US highways interstates?

U.S. Highways vs.
An interstate is a roadway that crosses state lines, but a highway is a major roadway that connects cities and towns. Here’s the fun (read: confusing) part: All interstates are highways, but not all highways are interstates.

What makes a road considered 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 qualifies as a highway?

Vehicle and Traffic Law §118 defines “Highway” as “The entire width between the boundary lines of every way publicly maintained when any part thereof is open to the use of the public for purposes of vehicular travel.” which by its terms includes the right of way however measured or acquired.