Editing Traffic light (section)

== In other contexts ==
The symbolism of a traffic light (and the meanings of the three primary colours used in traffic lights) are frequently found in many other contexts. Since they are often used as single spots of colour without the context of vertical position, they are typically not comprehensible to up to one in ten males who are [[colour blindness|colour blind]].{{Citation needed|date=October 2014}}

Traffic lights have also been used in computer software, such as the [[macOS]] [[user interface]], and in pieces of artwork, particularly ''[[Traffic Light Tree]]'' in London, UK.

=== Racing ===
{{see also|Racing flags}}
Automobile racing circuits can also use standard traffic signals to indicate to racing car drivers the status of racing. On an oval track, four sets may be used, two facing a straight-away and two facing the middle of the 180-degree turn between straight-away. Green would indicate racing is underway, while amber would indicate to slow or while following a pace car; red would indicate to stop, probably for emergency reasons.

[[Scuderia Ferrari]], a [[Formula One]] racing team, formerly used a traffic light system during their pit stops to signal to their drivers when to leave the pits.{{Citation needed|date=December 2009}} The red light was on when the tires were being changed and fuel was being added, amber was on when the tires were changed, and green was on when all work was completed. The system is (usually) completely automatic. However, the system was withdrawn after the [[Singapore Grand Prix|2008 Singapore Grand Prix]], due to the fact that it heavily delayed [[Felipe Massa]] during the race, when he was in the lead. 

Usually, the system was automatic, but heavy traffic in the pit lane forced the team to operate it manually. A mechanic accidentally pressed the green light button when the fuel hose was still attached to the car, causing Massa to drive off, towing the fuel hose along. Additionally, Massa drove into the path of [[Adrian Sutil]], earning him a penalty. He finally stopped at the end of the pit lane, forcing Ferrari's mechanics to sprint down the whole of the pit lane to remove the hose. As a result of this, and the penalty he also incurred, Massa finished 13th. Ferrari decided to use a traditional "lollipop" for the remainder of the [[2008 Formula One season|2008 season.]]

Another type of traffic light that is used in racing is the Christmas Tree, which is used in [[drag racing]]. The Christmas Tree has six lights: a blue staging light, three amber lights, a green light, and a red light. The blue staging light is divided into two parts: Pre-stage and stage. Sometimes, there are two sets of bulbs on top of each other to represent them. Once a driver is staged at the starting line, then the starter will activate the light to commence racing, which can be done in two ways. If a Pro tree is used, then the three amber lights will flash at the same time. For the Sportsman tree, the amber light will flash from top to bottom. When the green light comes up, the race officially begins but if a driver crosses the line before that happens, then a red light will come up and that will be a foul. {{citation needed|date=March 2019}}

=== As a rating mechanism ===
{{See also|Traffic light rating system|European Union energy label}}

The colours red, amber, and green are often used as a simple-to-understand rating system for products and processes. It may be extended by analogy to provide a greater range of intermediate colours, with red and green at the extremes.<ref>{{cite web|title=Traffic Light Song|website = [[YouTube]]| date=16 June 2017 |url=https://www.youtube.com/watch?v=db0HqnDU5MI |archive-url=https://ghostarchive.org/varchive/youtube/20211211/db0HqnDU5MI| archive-date=11 December 2021 |url-status=live}}{{cbignore}}</ref>