New Federal Law Legalizes Flashing Third Brake Lights to Cut Down on Rear-End Collisions

The Collision Avoidance Systems Act of 2025 is short, sweet, and focused on one thing: making your car’s high-mounted stop lamp (that third brake light in the rear window) flash briefly when you hit the brakes. The goal is to grab the attention of the driver behind you faster, potentially reducing those annoying and costly rear-end fender-benders.

The Blink-Blink Rule: What’s Legal Now

This bill sets the precise legal standard for what a “pulsating light system” must look like. When you press the brake pedal, the third light is allowed to flash quickly—no more than four times, and the entire flash sequence must be over in 1.2 seconds. After that fraction of a second, the light must immediately switch to a steady, constant glow, just like a normal brake light. If you’re stuck in stop-and-go traffic and tap the brakes repeatedly, the system won't flash every single time. The bill mandates a five-second “lock-out” period after you release the brake before the rapid pulsing can happen again. This prevents the light from flashing continuously, which would just be distracting and defeat the purpose.

How This Affects Your Commute

For most drivers, this is a safety upgrade that will likely happen without them lifting a finger, as auto manufacturers and aftermarket parts companies adopt the new standard. If you’ve ever been rear-ended while stopped at a light because the driver behind you was momentarily distracted, you know how critical those few extra milliseconds of reaction time can be. The theory is that this distinctive flash is far more attention-grabbing than a standard light turning on, especially in heavy traffic or low-visibility conditions. By formally allowing this specific technology, the law removes any ambiguity that might exist under various state and federal lighting regulations.

The Bureaucratic Fine Print

The law doesn't just flip a switch; it kicks off a regulatory process. It directs the Secretary of Transportation to create the necessary performance standards and formally update Federal Motor Vehicle Safety Standard Number 108 within 180 days of the bill becoming law. This step is crucial because it ensures that all authorized systems meet strict safety and performance criteria. It’s the difference between a carefully engineered safety feature and a random, annoying strobe light. This process ensures that the lights are bright enough to be seen but not so bright or frequent that they cause glare or confusion for following drivers. Essentially, the government is defining the guardrails so this technology can be widely adopted safely, making our roads just a little bit safer for everyone.