Brake lights w/ adapative cruise control?

Yep I remember.

Not sure where you are going with all of this in relation to my point. I mean we can also toss in that any car will decelerate differently depending on the grade the car is on that particular moment, for example a car going up a steep hill will decelerate as much just by releasing the accelerator pedal as the same car in the same gear on level ground when stepping on the brakes.

Let me try rewording my opinion more verbosely if that will help. Compared to an average car's deceleration level while in the standard driving gear for a particular speed, or in "Drive" in the case of an automatic, the brake lights on a hybrid or BEV should come on if coasting regen exceeds that amount of deceleration by a noticeable amount. If you are saying that you disagree with this because some people as part of their normal driving use their transmission and engine to slow down instead of their brakes, that's fine. I guess we just disagree then.

Also as a reminder I was replying to someone who felt that the brake lights on the Prius should come on anytime the car decelerates, and I gave my opinion that I would agree with that only if that was true for non-electric cars also, as I stated "I think the goal for BEV's and hybrids should be to mimic as much as possible the brake lights on regular cars in terms of what level of deceleration will cause the lights to come on." The key phrase being "as much as possible".

 

The point is - PRIUS - either w/DRCC - or without - actually does this.

 

Just taking your foot off the accelerator pedal will cause the brake lights to come on when not using DRCC? I wasn't aware of that.

 

That's not what he meant.

It's actually really simple if you take DRCC out of the equation. The brake light comes on when you press the brake, that's it, just like a normal car. Obviously gentle braking is using regen, but that's moot, the brake light comes on with the brake pedal.

 

That's how I thought it worked. I was thrown by Alan's comment that it worked the same with or without DRCC. And FYI all of my comments have been related to non-DRCC use. I apologize if I have confused the conversation by talking about non-DRCC usage since the OP's post was about DRCC. As I think is already understood, the Prius DRCC will activate the brakes if needed, resulting in the brake lights coming on. Although technically activating the brakes simply means increasing regen to a level similar to depressing the brake pedal. I think in another thread someone commented that DRCC will never brake hard enough to activate the friction brakes, only PCS will do that, although I'm not sure if that's true in all cases.

But again I was responding to a comment where someone stated their opinion that they felt DRCC should active the brake lights during any deceleration, which seemed to imply even during coasting regen. I said I would agree only if it also did that during non-DRCC use, leading to replies to my post which then took us a down a separate discussion of how brake lights work or should work during non-DRCC coasting and even a discussion about how non-electric cars decelerate in comparison. Interesting discussion but probably too many nuances to have going on in one thread, sorry about that.

 

I saw that too, but I disagree with it. At least for the Gen4 anyway. Maybe older generations work differently.

I've had cars slow down in front of me at every level from gently coasting through to full on emergency stops, and in every case my car has applied the right amount of braking and kept a safe distance.

Due to physics (specifically that every 5mph increase in speed roughly doubles the kinetic energy), the higher your speed, the less you feel regenerative braking. At high speeds (e.g. 50mph and above) you barely feel even maximum regenerative braking. It wouldn't be enough on its own to make DRCC practical. Try it and see... Go fast, then press the brake pedal just enough so that the bar on the accelerator guidance screen gets to the bottom of the gauge. If you do the same at 10mph you'll feel like you've slammed on the brakes. My car has braked much much harder than what you can get from regen alone many many times, and you can often hear the friction brakes scraping.

 

That also suggests that the brake lights do NOT come on with the "normal" cruise control actions.......but ONLY if you have the "adaptive" variety......and only then with abrupt slow-downs.

So the answer to the original question is: NO. If you have the classic "normal" cruise control, the brake lights will not come on due to any action by the cruise control.

 

And why does this occur? Isn't it because some drivers will overreact and brake too abruptly? I believe this will occur whether the car ahead has its brake lights on or not. I would contend that this would occur less often if the driver who brakes too abruptly has more warning that the car ahead is slowing. I suspect that the only reason brake lights come on only when pressing the brake pedal is that up until now the technology has not existed to turn on the brake lights whenever the car slows. It was much easier simply to wire the brake light switch to the pedal. I would like to see a study comparing traffic flows under the current system versus the one that I would prefer.

 

While I do agree that there should be a threshold level where regen braking does trigger the brake lights, I do believe it should be set high enough to that regen equivalent to a single notch downshift of a regular transmission car doesn't trigger the lights.

 

I agree that the technology now exists to implement on all cars brake lights that are activated by deceleration rate, and that studies should be done (maybe they are already) to determine what that rate should be, both for safety and traffic flow. There's probably no perfect number, but at least if it is standardized it will avoid the outlying situations like brake lights coming on just because someone disengages cruise control, or failing to come on when someone slows using engine braking.

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Whoa I didn't realize until you said that that the OP is apparently driving a Gen 3 (unless they haven't updated their profile). So we have been all over the place, which is good in one sense it's an important safety topic, it just made it a little hard to keep track of the conversation without a scorecard:

Hybrid/BEV deceleration without cruise control
Hybrid/BEV deceleration with cruise control
Hybrid/BEV deceleration with DRCC
Non-electric deceleration in standard gear
Non-electric deceleration in lower gear (manual)
Non-electric deceleration in lower gear (automatic)

In a previous thread awhile back I said I think there should be an indication on the dash whenever the brake light is activated by the system. The reason I believe this is because a brake light is after all a signal to other drivers. In all other cases the driver knows when they are signaling to other drivers because it is their action that causes it, such as a using the turn signal, putting the car in reverse, flashing the headlights, or stepping on the brakes. However when the system activates the brake lights the driver is left guessing, unless they happen to have a Kenworth on their tail with a chrome bumper to provide a reflection.

 

Not a record for quickness. BTDT, 3 days (though not in my Prius).

I seem to remember someone here being a same-day victim.

I.e. get your own air pump, whether a 12V electric or a floor-standing bicycle pump.

 

A long time ago, maybe the 1960s or early 1970s, the government experimented with a brake light in the back window that blinked. The blinking speed was related to how fast you were decelerating. If someone ahead of you slammed on their brakes, you'd see the light flashing furiously and know to slam on your brakes too.

It was very effective and was proven to help prevent accidents, but for some reason it was never adopted, though the rear brake light in the window did catch on and become a standard.

If we had this, you could make it so it wouldn't matter if you tapped your brake light or used regen. All that mattered was that you were slowing down, and the light would blink slow or fast depending on how much you were slowing down.

Edit add: found out that the guy who invented the rear window brake light also invented the flashing brake light, Dr. John Voevodsky. Apparently drivers were annoyed with the flashing light. (I remember seeing it as a kid and thought it was cool).

 

I see the blinking brake light on motorcycles occasionally. I think it is an improvement.

 

I was following a co-worker one time and suddenly his brake lights started flashing, I thought he was doing it on purpose to send me some type of message. I eventually realized that's how his brake lights worked all the time. I forgot to ask him if that was some type of modification. I now assume it was since I have never seen it since.

Not sure if all cars should do it all the time, imagine what rush hour would look like! But what might be good would be that light pressure on the brakes they would light normally, but if you press harder on the brakes then they would flash. Not sure what the threshold would be but at least you would get a better idea of what the driver is doing.

 

Such a system could have prevented my 2010 from getting hit in a chain reaction.

Traffic on all lanes of I-5 was very gradually slowing, so all vehicles had brake lights on. Then it suddenly converted to hard braking, without a change of brake lights or any other warning. I stopped in time with adequate margin, so did the first car behind me with almost no margin. But the second car behind had an inexperienced teenage driver, and she didn't notice in time, causing a chain reaction crash.

If the sea of solid but calm red lights also had a wave to rapidly flashing red lights, we would have had earlier warning of the abrupt change, and wouldn't have had to rely solely on visual depth perception.