Yellow lensThe middle section: steady yellow warns that red comes next.
Green lensThe bottom section: a steady green means go.
PoleHolds up the mast arm, the pedestrian head and the pushbutton.
Mast armHolds signal heads over the road. A rigid arm fixed to the pole.
Signal headOne complete set of lights facing one direction of traffic.
Pedestrian signal headShows a walking person for walk, an upraised hand for don't walk.
PushbuttonPressed by a pedestrian to ask for the walk signal.
At the corner 1
Controller cabinetHolds the controller that times the lights.
One signal head 3
VisorShades the lens and aims the light at approaching drivers.
BackplateA border round the head that makes the lights easier to see.
HousingThe case that protects each light and its parts.
How this list was compiled: Read 2026-09-23. (1) U.S. Federal Highway Administration, Manual on Uniform Traffic Control Devices, 2009 edition: section 1A.13 definitions, https://mutcd.fhwa.dot.gov/htm/2009/part1/part1a.htm (signal backplate, signal housing, signal lens, signal section, signal visor, pedestrian signal head with the walking person and upraised hand symbols, pushbutton, cantilevered signal structure also called a mast arm, controller assembly in a cabinet); chapter 4D, https://mutcd.fhwa.dot.gov/htm/2009/part4/part4d.htm (signal faces, the meanings of red, yellow and green, pole-mounted and overhead faces). (2) Wikipedia, Traffic light, https://en.wikipedia.org/wiki/Traffic_light: signal heads of three aspects, red, amber and green arranged vertically in that order; visors and back panels; lamp housing; mast arms and poles; a controller in a nearby cabinet; pedestrian signals and push buttons. Licence: own work
The drawing: Drawn for this site by script, 2026-09-23. Licence: own work
How it works
A traffic light is a signal head of red, yellow and green lenses, hung from a mast arm or fixed to a pole. At the corner stand the pedestrian signal, its pushbutton and the controller cabinet.
Read the full guide
Red, yellow, green, top to bottom
A vertical head has red at the top, yellow in the middle and green at the bottom, so the order can be read without the colours. Each light sits in the housing under its visor, and a backplate borders the whole head.
At the corner
The mast arm holds heads over the lanes; more can be fixed to the pole. A pedestrian presses the pushbutton to call the walk signal, a walking person; the upraised hand means don't walk. The controller in the cabinet times them all.
Questions and answers
What are the parts of a traffic light called?
The signal head, with its red, yellow and green lenses, housing, visors and backplate, hangs from a mast arm on a pole. Near it are the pedestrian signal head, the pushbutton and the controller cabinet.
What order are the colors on a traffic light?
On a vertical signal, red is at the top, yellow in the middle and green at the bottom. On a horizontal signal, red is on the left and green on the right.
What is the visor on a traffic light for?
It aims the light at the drivers it is meant for and shades the lens from sunlight, which would otherwise make the light harder to see.