Since the first Indianapolis 500 in 1911, the officials have signaled to the drivers out on the track with different-colored flags. Each color conveys a different message or warning. The famous checkered flag has been used since the very beginning, but over the decades, the other colors have had different assignments. The following is a summary of the different indications over the years.

For a list of starters (the “flagman”) see Indianapolis 500 Officials.

1911 to 1929

Beginning with the first “500” in 1911, the flag colors were as follows. Most notably, the red flag was used to start the race and indicate a clear course safe for racing. This is interestingly, quite opposite of modern standards. Initially, separate flags were used to indicate an accident on the course versus a caution warning. In the first few years, a yellow flag instructed drivers to stop immediately because the course was blocked. The blue flag was used to indicate specifically that there was a crash on the course. In 1922, the instructions for the yellow flag were changed to a warning of unsafe conditions. Drivers were instructed to slow down, hold their positions, keep their cars “under control”, and watch out for danger. The blue flag still meant a crash.

The green flag was used to signal that a driver was starting his final lap. It was not given to the entire field at once, but only to the specific driver at a time. Owing much to the “marathon” nature of the race during the early decades, the margins between each running position were usually rather sizable. In addition, after the winner crossed the finish line, the remaining cars on the track were allowed to complete the full 500 miles, even if they were still many laps behind. The officials would carefully keep track of each car’s lap count, and display the green flag for them individually when their final lap commenced.

The white flag was used to summon a car to the pits for consultation (similar to the way the black flag is used in modern times).

Dating back to the first “500” as well as the early races at the Speedway, the famous checkered flag was displayed to the winner as he crossed the finish line. It was then held back, and individually displayed to each subsequent finisher when he finished the 500 miles, even if that was several minutes (or even hours) later.

Flag	Color	Description
	Red	Start / Clear course
	Blue	Accident on course
	Yellow	Caution / Slow down
	White	Return to pits for consultation
	Green	Final lap
	Checkered	Race completed

In 1929, a new flag was added, a precursor to the modern day blue “courtesy flag”. The black flag with a white center was dubbed the “Move Over” flag. It was displayed to slower drivers to alert them that faster cars were approaching and were attempting to pass. This particular flag color combination would only be used for one year.

Flag	Color	Description
	Black with White square	Move over, others are overtaking

1930 to 1936

In 1930, in an effort to improve the flag signals, as well as better align them with the similar signals being used on public roads and highways, as well as railroads, the color scheme was revamped. For the first time, the green flag would be used to start the race and indicate a clear course safe for racing. In simple terms, green meant “Go!” The yellow flag was permanently established as the caution warning for all types of incidents, instructing drivers to slow down and hold positions. A separate flag for accidents was eliminated.

The red flag was changed to “Stop” – a specific command that had not been used for several years. The color red was already at the time widely recognized as a universal sign of “danger“. Most railroads had been using red for “stop” since the 19th century. It is unknown as to why the AAA Contest Board and the Speedway originally used the color red for “go” at their races.

The white flag remained the consultation flag, and the solid “King’s Blue” flag was changed to final lap. The newer “Move Over” flag from 1929 was kept, but was changed to the more visible orange with a blue circle.​

In 1935, a series of green and yellow lights were installed around the track at various intervals to supplement the flag signals from the starter’s stand.

Flag	Color	Description
	Green	Start / Clear course
	Yellow	Caution / Slow down / Maintain position
	Orange with Blue Circle	Move over, others are overtaking
	White	Return to pits for consultation
	Red	Stop
	Blue	Final lap (“King’s Blue”)
	Checkered	Race completed

1937 to 1941

Some small changes were made to the flags in 1937, but only to the supplemental signals. The primary green, yellow, and red flags were unchanged. The “Move Over” flag was changed to solid blue, and the final lap was changed to white. From now on, the consultation flag was changed to the now-familiar black flag, and would be accompanied by the car number displayed on a board.

The revisions made in 1937 brought the flag signals in line to nearly what they are in the present day. After the 1941 race, the Speedway shut down for World War II, and the “500” was not held in 1942–1945.

Flag	Color	Description
	Green	Start / Clear course
	Yellow	Caution / Slow down / Maintain position
	Blue	Move over, others are overtaking
	Black	Return to pits for consultation
	Red	Stop
	White	Final lap
	Checkered	Race completed

 

1946 to 2024

After the conclusion of World War II, the Indianapolis 500 resumed in 1946. Only one small change was made to the flags. The “Move Over” flag was changed from solid blue to blue with a diagonal orange stripe. The AAA Contest Board ceased their sanctioning of automobile racing after 1955, and was replaced by USAC in 1956. No changes were made to the flags at that time. At some point by the 1980s, the blue “Move Over” or “Courtesy” flag was changed slightly again – this time to solid blue with a diagonal yellow stripe.

In modern times, the flags are and have been used during practice and time trials in addition to race day. But this is largely limited to the green and the yellow. During time trials, the four lap qualifying runs typically see the green flag waved to start the run, followed by a green flag gently displayed at the completion of lap 1, and again at the completion of lap 2. At the conclusion of lap 3, the white flag is normally waved (in place of the green) to signify one lap to go. The run is then concluded with the checkered flag. Beginning in 1974, teams have been supplied with a separate green and yellow flag (to be waved by the crew) to indicate to the officials their desire to start/continue the run (green) or that they have elected to “wave off” the run (yellow).

During practice, the green flag is waved to start the session, and to resume the session after a caution period. After that, the green lights around the track control. In recent times, the checkered flag is displayed to formally conclude the practice session, rather than the red.

Flag	Color	Description
	Green	Start; Clear course
	Yellow	Caution; Crash, debris, or other hazard
	Blue with Diagonal Stripe	Faster car attempting to pass (“Courtesy” flag)
	Red	Stop
	Black	Return to pits for consolation or penalty
	White	Final lap
	Checkered	Finish; Race completed

In more recent years, two additional flags have seen occasional use. The Black flag with White cross (or white “saltire”) indicates that a driver has been disqualified and the officials have ceased scoring the car indefinitely. This would typically follow the driver having been displayed – and subsequently ignoring – the standard Black flag for either consolation or penalty. The Alternating Red and Yellow vertical striped flag indicates fluid (oil, water, or other liquid substance) is on the track, rendering it slippery and unsafe for racing conditions. On oval tracks such as Indianapolis, this flag is analogous to the standard yellow flag (merely giving further clarification of the unsafe condition), and results in the same caution period that a normal yellow flag would warrant.

Flag	Color	Description
	Red and Yellow Stripes	Oil, water or other substance on racing surface
	Black with White Cross	Disqualification; scoring ceased indefinitely

In 2007, the green flag had a white Ethanol logo emblazoned on it, as a gesture to the IndyCar Series moving to a “100%” renewable ethanol fuel (actually E90). In subsequent years, the checkered flags have featured the logos of sponsors, including Sunoco (2011–2018), Speedway gas stations (2019–2022), and Advance Auto Parts (2023–2024). Dating back to at least 2008, it has also been a custom for the 33 drivers in the starting field to autograph the two checkered flags that are waved at the finish.

Images courtesy of IndyStar.com, GoSunoco, IndyCar Fast Forward, and IndyCar.com

Yellow Lights

The first yellow light caution system had been installed at the Speedway in 1935. If an incident occurred on the track (crash, debris, etc.), the yellow lights would come on around the circuit, supplementing the yellow flag being waved by the flagman at the start/finish line. From 1935 through 1971, drivers were instructed to slow down to a prescribed speed and hold their positions under the yellow. The field was not bunched up behind a pace car. Passing cars and gaining track position was not permitted when the yellow lights were on, and infractions could be grounds for penalties. The Speedway management felt that drivers who were able to build up a large lead under green should not be penalized and lose that lead if a caution came out and the field were to be bunched up behind a pace car. Additionally, if the incident was minor, sometimes the yellow light condition was very brief. It was not unusual for a yellow light to last less than a lap, and the green turned back on after only a minute or so once the situation was deemed safe. Generally, officials wanted as much “natural” green flag racing as possible.

From 1972 to 1978, the Electro-PACER light number board system was utilized during caution periods. Similar in concept to the modern Virtual Safety Car (VSC) utilized in Formula One, and the similar “Slow Zones” at Le Mans, a series of number message boards were situated around the track, recording the intervals between the cars. To make things simpler, the intervals were displayed in “units of time”, not exact seconds. The object was to keep the numbers constant around the track. For example, if the caution period began, and a car’s interval was “5” units” behind the car in front of him, the driver was supposed to maintain “5” units of distance around the track. If the next board he encountered stated “4” units, the driver was going too fast, and needed to slow down a little. If the next board stated “6” units, the driver was lagging behind, and needed to speed up slightly. The boards even had three additional small lights on top, which were for “fine-tuning” and represented fractions of a unit.

By 1978, all other oval Indy car races and all other American oval track races (e.g., NASCAR) utilized a pace car for caution periods, packing up the field with the pace car ahead of the race leader. For safety, most drivers preferred the pack-up rule, conceding it would work for them just as many times as it might work against them. Emergency crews also preferred the pack-up rule, since it would concentrate the race traffic into one pack rather than having cars spread out all over the track. This would allow them to work on cleaning up crashes, debris, etc., with a clear track, and longer time gaps between cars passing through the work zone. After mixed results with the PACER system (and after new ways to “cheat” the system were discovered), USAC adopted the “pack-up” rule, in which the pace car (sometimes known as the safety car) leads the field during yellow flag conditions, beginning in 1979.

After the PACER Light system was scrapped, the lights around track were back to a two-light system – one green and one yellow at most locations. Some locations were standalone yellow lights (with no accompanying green), but these were mostly supplemental locations. When the track was safe for racing, the solid green light would be illuminated. During caution periods, a solid yellow light would be illuminated around the track. By no later than 2002, the green/yellow light system was upgraded to have rapidly-flashing yellow lights at all (or nearly all) locations around the track. The greens remained solid.

At the north part of the mainstretch, there was one location where a yellow light was mounted facing backwards (upstream). This was visible by the flagman in the starter’s stand, and also (for the most part) visible in some television shots looking north up the straightaway. This yellow light was once on the top of the catchfence, then in 1996 was re-mounted at a more conventional height. Supplemental beacon style yellow lights were added over the years in the sign board area.

In 2003, possibly in response to the controversial finish in 2002, green/yellow light system was further upgraded to add corresponding lights onto the backsides of the brackets at all (or nearly all) locations around the track. Among other reasons, this allows the green/yellow lights to be seen on television, and when called for in post-race analysis, conclusive video evidence is better available to tell when the green or yellow lights came on. Since television cameras are almost always pointing downstream, now the lights can be seen in the frame. Previously the lights could only be seen looking in the upstream directions.

At some point in the 2000s, a third light – a red light – was added to most of the fixtures to emphasize a fully-closed course. For 2025, a series of large, double-sided, supplemental LED light blocks were added around the track.

Flags as a symbol

The flags – particularly the checkered flag – have been synonymous with the Indianapolis 500 and the Indianapolis Motor Speedway (and racing in general) dating back to the very early years. The flags have been part of the Speedway’s famous “wing and wheel” logo for several decades. They have also been a fixture at the Speedway’s main gate and at the entrances to the Gasoline Alley garage area.

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