A road hierarchy is a system for categorizing roads. Road networks worldwide are typically organized according to one or more schemes:

While conceptually distinct, these classification systems often overlap in practice. Roads of higher administrative status typically serve higher functional roles and follow higher design standards, though exceptions are common. Most countries emphasize either functional or administrative classification for legal and planning purposes, while design standards are applied during implementation.

The related concept of access management aims to provide access to land development while ensuring traffic flows freely and safely on surrounding roads.

At the top of the mobility-access continuum in terms of traffic flow and speed are controlled-access highways. Their defining characteristic is the control of access to and from the road, meaning that the road cannot be directly accessed from properties or other roads, but only from specific connector roads. This indirection, in conjunction with high speed limits and multiple lanes, allows these roads to support fast traffic flow with high volume, in both urban and rural areas. They are at the bottom of the mobility-access continuum in terms of access to property, allowing access to almost nothing besides other roads and rest areas.

They are also known as freeways in the U.S., South Africa, and parts of Australia; as motorways in the U.K., New Zealand, and parts of Australia; and as expressways in numerous countries (though this term sometimes includes limited-access roads depending on the region).

Controlled-access highways do not have traffic signals nor at-grade crossings with other roads (intersections), railways, or pedestrian paths. When a road's path would intersect a controlled-access highway, the two roads will be vertically separated by an overpass (American English) or flyover (British English) or by a tunnel, preventing the need for an intersection. Pedestrian footbridges and tunnels are also grade-separated. The opposing directions of travel are separated by a median strip (American English) or central reservation (British English) generally a few meters to a few dozen meters wide, which may consist of a traffic barrier or a natural barrier like grass. This separation makes controlled-access highways a subset of divided highways (American English) or dual carriageways (British English). Generally, these roads prohibit pedestrians and vehicles not powered by a motor (e.g., bicycles). Parking is also generally prohibited.

Ramps (American English) or slip roads (British English) are special connector roads that allow traffic access to and from a controlled-access highway. Their length is normally on the order of several hundred meters in order to allow vehicles a sufficient distance to safely change speed while transferring from one road to the other road. The course of a ramp is often curved as needed in order to connect the two roads without sharp turns, which require vehicles to slow down considerably to traverse them safely. In many cases, a ramp may be subject to grade separation and use a flyover. In the US, where the standard term for a flyover is overpass (or underpass, when the road with level altitude is the higher road), the word flyover, which is less common, is reserved for those that carry ramps. Entrance ramps (or on-ramps) allow ingress traffic to enter the highway, and exit ramps (or off-ramps) allow egress traffic to exit the highway.

Ramps may be described by their orientation. A directional ramp curves toward the desired direction of travel, a semi-directional ramp exits on the side of the road opposite to the desired direction of travel, then curves back toward the desired direction, and a non-directional ramp curves away from the desired direction of travel (such as the looping ramps in a cloverleaf interchange).