Parts of a Road – Lanes, Shoulder, Crown and Layers

All 19 parts on the diagram

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Start here: 7 main parts 7

Lane The strip of road that one line of traffic travels in.
Sidewalk The paved strip beside a street for people walking.
Crosswalk The part of the road marked for people to walk across.
Center line Marks the split between lanes that run in opposite directions.
Curb The raised edge where the sidewalk meets the street.
Shoulder The strip right beside the traveled way, on each side.
Ditch A channel beside the road that carries water away.

A street from above 4

Bicycle lane A part of the road marked for people on bicycles.
Lane line Separates two lanes that run in the same direction.
Stop line A solid bar across the lanes showing where vehicles must stop.
Gutter A shallow channel beside the curb that carries rainwater away.

A road cut across 8

Traveled way The part of the road vehicles travel on, not counting the shoulders.
Crown The rise of the road's middle above its edges.
Surface course The top layer of the road, in direct contact with traffic.
Base course A layer of crushed stone or gravel that spreads the load downward.
Subbase A layer of cheaper material between the base course and the subgrade.
Subgrade The foundation of the road: the earth under all its layers.
Ditch slope (front slope) The slope from the shoulder's outer edge down to the ditch.
Back slope The slope from the ditch up to the top of the cut.

How this list was compiled: Read 2026-09-30; a name is kept only where two of these four use it. (1) Federal Highway Administration, Manual on Uniform Traffic Control Devices, 2009 edition, Section 1A.13, https://mutcd.fhwa.dot.gov/htm/2009/part1/part1a.htm : center line markings (the yellow lines that separate traffic lanes with opposite directions of travel), lane line markings (white lines that separate traffic lanes with the same direction of travel), stop line (a solid white line across approach lanes showing where a stop is to be made), crosswalk and crosswalk lines, sidewalk (the portion of a street between the curb line and the property line, intended for pedestrians), bicycle lane (a portion of a roadway designated for bicyclists by pavement markings), traveled way (the portion of the roadway for the movement of vehicles, exclusive of the shoulders). (2) US Navy, Engineering Aid 3 & 2, Vol. 2 (1983), chapter 5, https://archive.org/details/ERIC_ED249091 , its list and two figures of road nomenclature: surface (the portion of the road in direct contact with traffic), subgrade (the foundation of a road), base (select material placed over the subgrade to distribute the load), traffic lane, traveled way (both lanes of a 2-lane road), shoulders (the additional width immediately adjacent to each side of the traveled way), roadway ditch, ditch slope (from the shoulder's outer edge down to the ditch bottom), back slope (from the top of the cut down to the ditch bottom), centerline, crown (how much higher the centerline is than the edge of the traveled way). (3) US Army and Air Force, FM 5-430-00-1 (1994), https://archive.org/details/FM_5_430_0_1_P_D_R_A_H_T_O_R_D_1994 : traveled way, traffic lane, shoulder, crown, surface course, base course, subbases (materials used between the subgrade and base course), subgrade, roadside ditch, front slope or ditch slope and back slope, gutters (shallow paved drainage channels next to paved areas). (4) Wikipedia: Road, Lane, Road surface marking (lane lines, stop lines, crosswalks), Curb (the edge where a raised sidewalk meets a street), Street gutter, Sidewalk, Pedestrian crossing, Bike lane, Shoulder (road), Cross slope (a crowned road is highest at the center and drains to each side), Base course, Subbase (pavement), Subgrade. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Not to scale: heights in the second drawing are exaggerated. Licence: own work

How it works

A road is more than its surface. These are the names US highway manuals use for the lines and strips seen from above, and for the layers and slopes seen when a road is cut across.

Read the full guide

On a street, from above

Each line of traffic has its own lane. A lane line separates two lanes going the same way, and the center line separates the two directions. At an intersection drivers halt at the stop line, before the crosswalk. Rain runs to the gutter, against the curb, and the sidewalk is behind it. A bicycle lane is marked for riders.

Cut across, from the side

The two lanes together are the traveled way, with a shoulder on each side. The crown is the rise in the middle that sheds rain. Under the tires lies the surface course, then the base course, the subbase and the subgrade. Water collects in the ditch, between the ditch slope and the back slope.

On US roads the center line is painted yellow and lane lines are white.
The traveled way stops at the edge of the lanes. The shoulder is outside it.

Questions and answers

What are the parts of a road called?

On top: lanes, divided by lane lines and a center line, with a shoulder or a curb and sidewalk at each side. Underneath: the surface course, base course, subbase and subgrade. Beside a country road: the ditch, with a ditch slope and a back slope.

What is the side of the road called?

On a highway or country road it is the shoulder, the strip right beside the lanes. On a city street the edge is the curb, with a gutter on the street side of it and a sidewalk behind it.

What are the layers of a road?

From the top down: the surface course that traffic touches, the base course of crushed stone or gravel that spreads the load, the subbase of cheaper material below it, and the subgrade, the earth that is the road's foundation.

Why is the middle of a road higher than the edges?

So that water runs off. That shape is called the crown. On a straight two-lane road the surface is highest along the center line and slopes gently down to each side, toward the shoulders and the ditch or gutter.

What is the difference between a center line and a lane line?

A center line separates traffic going in opposite directions. A lane line separates two lanes going the same way. In the United States center lines are yellow and lane lines are white.