What Are the Three Brake Lights on a Vehicle?

The three brake lights on a modern vehicle are the left brake light, the right brake light, and the center high-mounted stop lamp (CHMSL), often called the “third brake light.” Together, they are designed to make braking more visible to drivers behind you and reduce rear-end collisions.

Understanding the Three Brake Lights

When people talk about “three brake lights,” they’re usually referring to the standard lighting arrangement at the rear of almost every passenger vehicle on the road today. This configuration is both a safety feature and a legal requirement in many countries, developed over decades of research into how to make braking intentions clearer to other road users.

1. Left Brake Light

The left brake light is mounted at the rear left side of the vehicle and illuminates when the driver presses the brake pedal. It is typically integrated into the left rear combination lamp, which may also contain the left turn signal and tail light.

This lamp helps following drivers on the left side recognize that the vehicle is slowing or stopping. It is especially important in multi-lane traffic or when a vehicle is partially obscured from the right side, such as on curved roads or during lane changes.

2. Right Brake Light

The right brake light mirrors the left brake light and is positioned on the rear right side of the vehicle. Like the left lamp, it illuminates when the brake pedal is pressed and is usually part of a multi-function rear light cluster that also includes the right turn signal and tail light.

Because traffic often overtakes on one side depending on the country (left or right), having a distinct right brake light ensures that drivers approaching from that side clearly see braking, even if their line of sight to the other lamps is blocked.

3. Center High-Mounted Stop Lamp (CHMSL) – The “Third Brake Light”

The third brake light, formally known as the Center High-Mounted Stop Lamp (CHMSL), is installed higher than the left and right brake lamps. It is typically located at the top of the rear window, on the trunk lid, or integrated into a rear spoiler, shining directly at the eye level of drivers in following vehicles.

This lamp provides an additional, highly visible signal that the vehicle is braking, especially useful when the standard brake lights might be obscured by other vehicles, road geometry, or glare. Research has shown that CHMSLs noticeably reduce rear-end collisions by giving trailing drivers an earlier, clearer visual cue that the vehicle ahead is slowing.

Why Three Brake Lights Matter for Safety

The three-brake-light system is not just a design choice; it is the result of safety research, regulation, and real-world crash data. The layout is intentionally redundant and highly visible to compensate for poor weather conditions, traffic congestion, and human reaction time.

How the Three Lights Work Together

Together, the two lower outer brake lights and the higher center lamp create a distinctive lighting pattern that clearly communicates braking to following drivers. This triangular arrangement of red light draws visual attention and helps trailing drivers react more quickly and accurately.

The key combined safety benefits of the three-light configuration can be described as follows:

• They provide redundancy so that if one lamp fails, others still communicate braking.
• They create a wider visual signature across the rear of the vehicle, making the braking signal easier to notice in traffic.
• The high-mounted center light cuts through visual clutter from other vehicles’ lights and road signs.
• They improve visibility in bad weather, including fog, heavy rain, and snow.
• They help distinguish braking from tail lights or running lights, which can otherwise look similar at night.

Together, these features mean the three brake lights do more than just glow red: they create a clear, unmistakable warning to following traffic, significantly lowering the risk of a driver missing the signal that the car ahead is slowing down.

Legal and Regulatory Background

Today, three brake lights are standard on passenger vehicles in many regions, but that was not always the case. Their adoption followed federal regulations, international standards, and safety studies demonstrating measurable reductions in rear-end crashes.

Regulations in the United States and Other Markets

In the United States, the National Highway Traffic Safety Administration (NHTSA) mandated center high-mounted stop lamps for passenger cars starting with the 1986 model year and for light trucks and vans a few years later. The requirement is now incorporated into Federal Motor Vehicle Safety Standard (FMVSS) No. 108, which governs lighting on motor vehicles.

Many other regions, including the European Union, Canada, Australia, and parts of Asia, have parallel rules grounded in UN regulations (such as UN Regulation No. 48 and No. 7) or national standards. While the technical details and exact requirements can vary — such as minimum brightness, mounting height, and lens size — the essential idea is the same: vehicles must have a pair of rear stop lamps plus a high-mounted center stop lamp.

Common Misconceptions About Brake Lights

The phrase “three brake lights” can cause confusion, especially among new drivers or people unfamiliar with vehicle lighting terminology. Clearing up the most common misunderstandings helps drivers know what to expect and what’s legally required.

Not Three Separate Functions, but Three Stop Lamps

One frequent misconception is that there are three different kinds of brake lights with distinct functions. In reality, all three are stop lamps: they serve the same core purpose and typically illuminate simultaneously when the brake pedal is pressed.

They may, however, be integrated into multi-function units with other lighting roles, such as tail lights (for nighttime running), turn signals, and hazard lights. On some vehicles, the same red bulb or LED array may operate at different brightness levels for tail and brake functions, but when people refer to “three brake lights,” they are talking about the three distinct brake/stop light locations, not three functions.

Maintenance and Safety Checks

Because brake lights are a primary safety feature, keeping all three in working order is crucial. Malfunctioning brake lights not only increase crash risk but can also lead to traffic stops and fines, depending on local laws.

How Drivers Should Check Their Three Brake Lights

Drivers can perform simple routine checks to ensure all three brake lights are working correctly and remain clearly visible. These checks do not require special equipment and can be done in a driveway or parking lot.

The basic steps for checking brake lights can be summarized in these practical actions:

1. Park the vehicle on a flat, safe surface, ideally facing a wall or in front of a reflective surface at night.
2. Press and hold the brake pedal while the vehicle is in “Park” (automatic) or with the parking brake engaged (manual).
3. Use a reflection in a window, garage door, or wall to see whether the left, right, and center brake lights all illuminate.
4. If no reflective surface is available, ask another person to stand behind the car while you press the brake pedal.
5. If a light is out, replace the bulb or have a technician inspect the wiring or LED unit, depending on the vehicle’s design.

By following these simple steps, drivers can catch problems early, ensuring all three brake lights remain reliable and visible whenever they slow or stop.

The Role of Modern Technology

While the traditional layout of three brake lights has stayed fairly constant, the technology behind them continues to evolve. Many newer vehicles use LEDs (light-emitting diodes) for their brake lamps instead of conventional incandescent bulbs.

LED Brake Lights and Advanced Features

LED brake lights switch on faster than incandescent bulbs, are more energy-efficient, and often last longer. This quicker illumination, even by fractions of a second, can give following drivers a slightly earlier warning, potentially shortening reaction times in an emergency.

Some manufacturers also incorporate adaptive or “emergency” brake light functions: during hard braking, the brake lights may flash rapidly or increase intensity (where regulations allow) to signal an urgent stop. In all these configurations, however, the principle of three distinct brake light positions — left, right, and center high-mounted — remains the foundation of the system.

Summary

The three brake lights on a vehicle are the left rear brake light, the right rear brake light, and the center high-mounted stop lamp (CHMSL), commonly known as the third brake light. All three illuminate when the driver presses the brake pedal, forming a highly visible, redundant signaling system intended to warn following drivers that the vehicle is slowing or stopping. This configuration, now mandated or strongly regulated in many parts of the world, has been shown to reduce rear-end collisions and is a cornerstone of modern vehicle safety. Regular checks and maintenance help keep these lights functioning properly, ensuring that this simple but vital safety system continues to protect drivers and passengers on the road.

What is the third brake light for?

Cars have a third brake light to increase safety by making it easier for other drivers to see when a vehicle is braking, thereby reducing the likelihood of rear-end collisions. The higher, central placement makes the light more visible, especially when the lower tail lights are blocked by other vehicles or trucks.
 

• Improved visibility: A high-mounted third brake light is more visible to following drivers, who may be able to see through other cars or trucks to spot the light. 
• Increased reaction time: The additional signal gives drivers behind a better chance to react and brake themselves, which can prevent accidents. 
• Legal requirement: The third brake light, also called the Center High Mount Stop Lamp (CHMSL), has been mandatory on new passenger cars in the U.S. since 1986 and on new light trucks and vans since 1994. 
• Reduced crashes: Studies, including those conducted by the National Highway Traffic Safety Administration (NHTSA), have shown that the third brake light reduces rear-end collisions and injuries. 

Does the 3rd brake light have to work?

Yes, in most places, the third brake light is legally required to work, though specific state inspection rules can vary. It has been mandatory on new passenger cars since 1986 and on new light trucks since 1994, and it is a violation of federal law to have it out. Driving with a non-functional third brake light can lead to being pulled over, failing a safety inspection, or being at a higher risk of being rear-ended. 
Why it’s required

• Safety: The third brake light, or Center High Mounted Stop Lamp (CHMSL), is designed to be more visible to following drivers, which helps reduce rear-end collisions. 
• Federal law: Federal regulations mandate that new vehicles must be equipped with a CHMSL. 
• State inspection: Many states require all factory-installed equipment to be functional, meaning a third brake light must pass a safety inspection if the vehicle is equipped with one. 

Consequences of a non-working light

• Traffic stop: You can be pulled over by law enforcement for a burnt-out light, as it is a violation of the law. 
• Inspection failure: Many states require that all lights on the vehicle be in good working order to pass a safety inspection. 
• Increased accident risk: A non-working third brake light eliminates a key safety feature, increasing the likelihood of a rear-end collision. 

When were 3rd brake lights mandated?

1986
The National Highway Traffic Safety Administration (NHTSA) repeated Voevodsky’s experiment on a larger scale, and concluded that center high mounted stop lamps, as the government calls them, reduce accidents and injuries. As a result, in 1986, NHTSA began requiring all new cars to have a third brake light.

What are the three lights in the taillight?

The three bulbs in a typical tail light assembly are for the tail light, brake light, and turn signal light. Many modern vehicles use a dual-filament bulb for the tail and brake lights, while a separate bulb is used for the turn signal. The third bulb is often dedicated to the reverse light, which illuminates when the car is in reverse. 

• Tail Light: This is a red light that provides visibility at night and turns on automatically with your headlights. 
• Brake Light: A brighter red light that indicates the vehicle is slowing down or stopping. It is activated when you press the brake pedal. 
• Turn Signal: An amber or red light that flashes to show your intention to turn or change lanes. It is activated by using the turn signal lever. 
• Reverse Light: A white light that turns on when you put the car in reverse, helping you see behind the vehicle at night.