Phantom braking is when one car slows down around a turn or for some other reason (besides actually needing to stop), and then the car behind them applies the brakes, so the car behind them applies the brakes, and so on.
This effect is great enough that it often causes traffic jams.
Maybe this is a chance to reexamine brake signals. Traffic jams are a huge problem as roads become more and more crowded.
I think that brake light brightness should correspond with how hard the driver presses the brake and how long they apply the brake.
So in a situation on a highway, as a car goes around a curve with other cars close behind, they can tap the brake without looking like they're slamming on the brake. There's a huge difference.
If the brake lights gradually increased brightness based on how hard or how long the pedal was pressed, it would be more accurate and eliminate phantom traffic jams.
Alternatively, brake brightness could also be based on speed. As brakes are pressed harder or longer, the car's speed decreases. The closer they are to physically stopping, the brighter the brake lights need to be, because it's more important that the car behind also stops.