The third brake light became mandatory on new U.S. passenger cars beginning September 1, 1985. Known officially as the center high-mounted stop lamp, or CHMSL, it was introduced to make braking easier for following drivers to see. The rule did not apply to every vehicle type at the same time: federal requirements for many light trucks and vans began later. Knowing the distinction helps explain why some older vehicles—and some vehicles first sold in the same era—do not have a third brake light.
No. The 1985 requirement applied to new passenger cars covered by the federal standard. Other vehicle categories did not all receive the same effective date. Light trucks, vans, and multipurpose passenger vehicles (MPVs) were covered by a later federal requirement, which took effect for applicable vehicles manufactured on or after September 1, 1993.
Vehicle classifications can be less obvious than everyday descriptions. A vehicle marketed as a family vehicle may be classified under federal rules as a passenger car, an MPV, or a light truck, depending on its design and regulatory category. As a result, a vehicle’s body style or name alone may not establish which production-date requirement applied.
The table summarizes the main federal dates. It is a general guide rather than a substitute for checking the standard and vehicle classification for a particular model.
| Vehicle category | General federal requirement date | What the date means |
|---|---|---|
| Passenger cars | September 1, 1985 | Covered new passenger cars manufactured on or after the effective date had to have a compliant CHMSL. |
| Applicable light trucks, vans, and MPVs | September 1, 1993 | The later requirement extended the high-mounted stop lamp to covered vehicles in these categories. |
For questions about an individual vehicle, its certification label, owner’s manual, and original equipment information can help identify its classification and build date. NHTSA’s regulations and interpretations are the authoritative sources for regulatory details.
Why Do Some 1985 Cars Have a Third Brake Light?
Some vehicles identified as 1985 models were manufactured after the September 1 cutoff, while others were built earlier. Automakers may also introduce changes during a model year, and vehicle production schedules differ. Therefore, two cars with the same model year can have different factory equipment.
There are also vehicles that received a CHMSL before the federal deadline. An automaker could install the lamp early, either as part of a design decision or in anticipation of the upcoming requirement. A lamp’s presence does not by itself establish that the vehicle was legally required to have it on its production date.
When checking a specific car, the build date on the certification label is more useful than relying only on the year printed on registration paperwork. The vehicle identification number (VIN) can help identify the model and production information, but the VIN does not always make the exact build date obvious without manufacturer records or a vehicle-history lookup.
Are Owners Required to Add a Third Brake Light to an Older Car?
The federal rule generally sets manufacturing requirements for vehicles and their original equipment. It does not generally require owners to retrofit a third brake light on a vehicle that was manufactured before the applicable federal cutoff. A pre-rule vehicle is not automatically required to be modified simply because newer vehicles have the lamp.
That does not mean owners can ignore a lamp that is already installed. State inspection rules and vehicle-equipment laws may address required or installed lighting, and the details can vary by state. In some jurisdictions, a vehicle that has a factory-installed CHMSL may be expected to keep it operational to pass inspection or comply with local requirements.
Anyone considering removing, covering, or altering a third brake light should check the laws in the state where the vehicle is registered. Owners should also avoid changes that reduce the function of required stop lamps or create a misleading signal. When state rules are unclear, the state motor vehicle agency or inspection program is a more reliable source than informal advice.
What Should Drivers Check If the Third Brake Light Is Not Working?
On a vehicle equipped with a CHMSL, a failed lamp can reduce the visibility of braking and may cause an inspection problem. The right repair depends on the lamp design. Older vehicles may use replaceable bulbs, while newer models may use LED assemblies or lamps integrated into a rear spoiler or other body component.
- Check the owner’s manual. It can identify the lamp type, fuse locations, and safe replacement procedure.
- Inspect the light while the brakes are applied. A helper can check the rear of the vehicle, or a driver can use a safe reflective surface or recording device to confirm operation.
- Check for a failed bulb or fuse. If the main brake lamps also fail, a fuse, switch, wiring, or electrical fault may be involved.
- Look for water, damage, or loose connections. Moisture or damaged wiring can affect an exterior lamp assembly.
- Use the correct replacement part. The replacement should match the vehicle’s specifications and preserve the lamp’s required function.
If a new bulb or basic fuse check does not solve the problem, a qualified repair shop can test the brake-light switch, wiring, connectors, and control modules. Some vehicles require replacement of a complete LED assembly rather than a separate bulb.
Can an Aftermarket Third Brake Light Be Added?
Owners sometimes add an auxiliary brake lamp to a vehicle that did not originally have one. A well-designed addition can improve visibility, but installation should not interfere with the original lamps, obscure the rear window, create glare, or produce a confusing signal. The wiring should activate the lamp with the brake pedal, not continuously or at the wrong time.
Aftermarket equipment also needs to comply with applicable federal and state rules. Federal motor vehicle safety standards primarily govern new vehicles and equipment at manufacture, while state laws can govern the use and modification of vehicles on public roads. The applicable rules depend on the product, installation, and location.
Before installing an auxiliary lamp, the owner should verify that it is designed for automotive use, mounted securely, and compatible with the vehicle’s electrical system. A reputable installer can help avoid wiring faults and determine whether the modification could affect inspection or warranty coverage.
How to Verify a Vehicle’s Original Equipment
For a particular vehicle, several sources can help establish whether the third brake light was original equipment:
- Read the certification label. The label is commonly found on the driver-side door jamb or door edge and includes the vehicle’s manufacture month and year.
- Consult the owner’s manual. The manual describes the vehicle’s lighting equipment and may list the CHMSL in its bulb or maintenance section.
- Check manufacturer information. A dealer or automaker may be able to confirm original equipment using the VIN.
- Review the applicable federal standard. FMVSS 108 and NHTSA materials explain the requirements by vehicle category and effective date.
These checks are especially useful for vehicles built near a federal cutoff, imported vehicles, and vehicles that have undergone body repairs or modifications. A missing lamp may be the result of an accident repair or aftermarket change rather than the vehicle’s original design.
Reliable Sources for the Federal Rule
The primary sources for U.S. vehicle lighting requirements are NHTSA and the federal regulation itself. NHTSA publishes information about vehicle safety standards and explains how federal motor vehicle safety rules apply. The relevant regulation, FMVSS 108, is codified at 49 CFR § 571.108.
Readers can also consult NHTSA’s vehicle safety information and use its resources to look up vehicle safety information by VIN. For a state-specific question—such as inspection rules for a nonfunctional lamp—the state department of motor vehicles or the agency that administers vehicle inspections is the appropriate source.
In short, the third brake light became federally required on new U.S. passenger cars manufactured on or after September 1, 1985. Applicable light trucks, vans, and MPVs followed on September 1, 1993. Model year alone may not settle whether a specific vehicle was covered; its classification and actual manufacturing date matter.