Declaration can happen through a variety of means. Simply not accelerating would be the first one, due to friction. But even steadily accelerating on an upward slope would decrease the vehicle’s speed, and you don’t want to give vehicles behind the idea that a stop is being initiated.
You’ve spelled out the entire problem but have come to incorrect conclusions. If you’re directly behind a car, it becomes hard to sense acceleration or deceleration of other vehicles. More importantly, the brake is often used to decelerate on highways and not initiate a stop. This all leads to a lot of confusion and ultimately crashes every year.
The situations you mentioned are exactly the problem areas. Not accelerating it slowing down, often quite quickly, to make an exit. Dangerous. Going up a slope may or may not change speed, which needs to be known. Again dangerous. Same with downhill which is actually more dangerous not knowing how hard braking is happening.
So we have the technology to fix this. We can invent either variable break lights that change brightness or zoned lights that tell you “I’m slowing down” versus “I’m braking hard”. We could fix this because cars are dangerous enough as is
I always wanted a similar system to what you see in racing video games, when they display input controls. A red and green bar on the rear of the vehicle which shows accelerator pedal position, and a red bar which, in real life would have to show deceleration, as a percentage of theoretical maximum, rather than pedal position, as in the games.
Not a car, but I’ve got a bicycle light that does this. Turns on when it’s dark and also when you brake. So definitely possible
Technology Connections on YT has. Awhile rant about this. https://youtu.be/U0YW7x9U5TQ?si=SZaEzNCDKoLXhx83
That’s a fairly complicated system to replace what is just an ultra simple switch at the pedal. The latter is even pretty likely to last the life of the car.
The problem is with electric cars that can be driven with one pedal most of the time
I was thinking about this last time I drove an ev (ioniq 5). It will really decelerate quite hard when you lift off, and it’s configurable by the driver.
I don’t think they need to do it with an accelerometer, but if the regeneration system is applying more braking force than it would take to turn on the light with the brake pedal, it should turn the light on.
Either that or they should require the brake pedal to be used beyond that point.
Edit: actually it just occurred to me that it might be no worse than downshifting in a normal car. Maybe it’s not a big deal.
