An arterial road is a high-capacity road designed to move large volumes of traffic over long distances, connecting towns, cities, and major destinations. In the road classification system used by transportation agencies, arterials sit near the top of the hierarchy, just below freeways and interstates. They prioritize keeping traffic moving over providing direct access to homes and businesses, which is why they tend to be wider, faster, and have fewer driveways than the streets in your neighborhood.
How Road Classification Works
Every public road in the United States falls into a functional classification based on two competing purposes: mobility (how far and fast traffic moves) and access (how easily drivers can reach specific properties). Local streets sit at one end of this spectrum, providing direct access to homes and businesses but at low speeds over short distances. Freeways sit at the other end, offering high-speed travel with no direct property access at all.
Arterials fall just below freeways. Their primary job is mobility. Collectors, the next tier down, channel traffic from local streets and feed it onto arterials. Think of the system like a river network: local streets are small streams, collectors are tributaries, and arterials are the main channels carrying the heaviest flow toward freeways or between major destinations.
Types of Arterial Roads
Not all arterials are the same. The Federal Highway Administration breaks them into tiers based on how much traffic they carry and how far apart their connections are.
- Principal arterials serve the longest trips with the fewest access points. They connect major activity centers, carry the highest traffic volumes, and often have controlled intersections with traffic signals. Despite making up only about 3.8% of total road mileage in the U.S., they handle a massive share of all vehicle travel.
- Minor arterials serve trips of moderate length and bridge the gap between principal arterials and collector roads. They provide more connections to surrounding land than principal arterials do, but still prioritize through-traffic over local access. They account for roughly 5.9% of total road mileage.
In practice, a principal arterial might be a six-lane divided boulevard cutting through a metro area or a four-lane highway connecting two cities. A minor arterial might be the busy two- or four-lane road that runs through a suburban commercial strip, linking neighborhoods to the nearest highway.
What Arterials Look Like
Arterial roads are physically built to handle high traffic volumes and higher speeds. They typically range from two to four travel lanes in each direction, with lane widths of 10 to 12 feet. Rural arterials often have wide shoulders (8 to 10 feet) to accommodate high operating speeds of 60 mph or more. Urban and suburban arterials are more likely to have curbs, narrower shoulders, and lower speed limits.
Many arterials use raised or non-traversable medians to separate opposing traffic. These medians serve a specific purpose beyond safety: they prevent left turns across traffic at uncontrolled points, keeping vehicles in the through lanes moving. On well-designed arterials, traffic signals are spaced at least half a mile apart. When signals end up less than a quarter mile apart, speeds drop significantly and congestion builds.
Driveway access is deliberately limited. The more driveways that open onto an arterial, the more conflict points exist where turning vehicles slow down through-traffic or collide with other road users. Transportation agencies use access management guidelines to control how close driveways can be to intersections and to each other, keeping the road functioning as intended.
Arterials vs. Collectors and Local Streets
The easiest way to understand an arterial is to compare it to the roads it connects to. Collectors are typically two-lane roads that gather traffic from local streets and funnel it toward the arterial system. They run at lower speeds and serve shorter trips. You might drive on a collector to get from your subdivision to the main road; the main road is likely an arterial.
Local streets make up the vast majority of road mileage. They’re designed for low speeds, direct property access, and short trips. They have frequent driveways, stop signs, and intersections. Arterials are the opposite: fewer access points, higher speeds, and longer uninterrupted stretches. A local street gets you to your driveway. An arterial gets you across town.
Why Arterials Are Dangerous for Pedestrians
Arterial roads carry a well-documented safety problem. Between 2018 and 2022, arterials accounted for nearly 62% of all pedestrian fatalities in the United States, a total of 21,148 deaths, despite making up less than 10% of the nation’s total road mileage. Principal arterials alone were responsible for about 39% of pedestrian deaths while comprising under 4% of roads.
The reasons are straightforward. Arterials combine high speeds, high traffic volumes, and wide roadways, all of which make crossing on foot dangerous. Research has found that pedestrian collision rates increase by about 9% for every 10 additional feet of street width. Many arterials were designed primarily to move cars and lack adequate crosswalks, pedestrian signals, or safe refuge islands. When a pedestrian is struck at arterial speeds (often 40 to 55 mph), the likelihood of a fatal injury is dramatically higher than on a 25 mph local street.
This is why many cities are now retrofitting arterials with better pedestrian infrastructure, including shorter crossing distances, improved signal timing, and median refuges that let people cross one direction of traffic at a time.
Everyday Examples
If you’ve driven through any American city or suburb, you’ve used arterial roads. The wide, multi-lane roads lined with shopping centers, gas stations, and fast-food restaurants are typically minor or principal arterials. State highways that pass through towns often function as arterials. So do many of the numbered routes that connect smaller cities across rural areas.
You can usually identify an arterial by a few telltale signs: multiple lanes in each direction, traffic signals instead of stop signs, a posted speed limit of 35 to 55 mph (sometimes higher in rural areas), a raised median, and relatively long stretches between intersections. If a road feels like it was built to get you somewhere rather than to be somewhere, it’s probably an arterial.