Brake Lights or No Brake Lights. That is the question.

Discussion in 'Prime Main Forum (2017-Current)' started by schja01, Jul 20, 2019.

  1. schja01

    schja01 One of very few in Chicagoland

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    One thing I learned on a recent trip is if you are on Cruise Control and use the CC Stalk to lower the set speed substantially (from 55 to 30mph) the Prime will slow very aggressively. You can do this by just holding the stalk down and watching the set point decrement on the MID. It's either using aggressive Regen or the Physical Brakes or Both. I don't think it's B Mode as I don't feel the ICE spinning up.
    Either way it's very aggressive and I got to wondering if during this slowing the Brake Lights are engaged.
    My guess is if physical brakes are slowing the car the brake lights are probably used but if it's Regen then probably not.
    Does anyone know for sure?
    Thanks,
    J
     
  2. jb in NE

    jb in NE Senior Member

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    Why would you do this? It is much smoother to disengage the cruise, adjust your speed to the desired amount, then re-engage cruise control.
     
  3. sam spade 2

    sam spade 2 Senior Member

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    That has been discussed before for the older models......and the answer is NO the cruise control will NOT engage the brake lights.

    NOW.....on the newer models with "adaptive" cruise and/or things like "collision avoidance" I don't think that subject has come up.

    On many you can see the 3rd brake light reflected slightly in the back glass when it's on. Try to look for that.
     
  4. schja01

    schja01 One of very few in Chicagoland

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    “It is much smoother to disengage the cruise, ”

    Not sure I agree with that but if the brake lights don’t illuminate it would enter into my future decision.
    Tnx.
     
  5. schja01

    schja01 One of very few in Chicagoland

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    Interesting. Worth a try.
    Tnx.
     
  6. jb in NE

    jb in NE Senior Member

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    As you noted, putting in very large changes in the cruise setting cause the car to slow very aggressively. Unless this is how you normally drive, doing it manually will be much smoother.
     
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  7. m8547

    m8547 Active Member

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    On the Prime the cruise control will definitely turn on the brake lights, but usually only when the amount of braking passes where B mode usually is on the display that shows the amount of braking.
     
  8. ChapmanF

    ChapmanF Senior Member

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    Before I cancel cruise, I usually push down the go pedal to roughly where it would be if I were driving at the current speed. Then I pull the cruise stalk to cancel. That way the transition is very smooth (I aim for imperceptible) and then I can back off the pedal to slow down.

    It was easier in a conventional car where you could feel the pedal was lighter to press right until the point where the cruise servo was holding the cable. In a Prius there is nothing like that to feel, so you have to sort of guess, but it gets better with practice.
     
  9. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I’m a bit surprised there isn’t more automation support there, actually. It’s been 10 years since the introduction of ordinary cars with manual transmissions capable of doing automatic rev-matching as you row through the gears, why can’t a cruise control do a smoother handoff?
     
    #9 Leadfoot J. McCoalroller, Jul 20, 2019
    Last edited: Jul 20, 2019
  10. Tideland Prius

    Tideland Prius Moderator of the North
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    Don’t post garbage if you haven’t fact checked.

    This has come up for the 4th gen several times already (it’s been on the market for 3 years, you really think no new member has ever asked?)

    Yes. The brake lights come on. It’s in the manual.

    On the older models, I believe the lights come on if it brakes hard enough (basically the thresholds are be same as if you were operating the brake pedal). I don’t believe it’s a “definite no”.
     
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  11. m8547

    m8547 Active Member

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    I still have an issue with how this works on the Prime. The brake lights on every car I've ever driven come on with the lightest touch of the brake pedal, not even enough to slow down at all. When the cruise control is braking on the prime, the brake lights don't come on until it's braking moderately hard. That's a different behavior than if the driver is braking, and it potentially gives cars behind you less time to react if they are not expecting to brake.

    The Tesla model 3 shows the brake lights on the display. It has one pedal driving, and you have to be slowing down moderately hard before the brake lights come on. Similar to cruise control on the prime, but all the time. It would be interesting to collect statistics on which cars are rear ended most often. The model 3 also has tiny brake lights, I think just eight LEDs each, which can't be optimal for visibility. Although I think certain Camrys are worse with just six LEDs, but I haven't seen one in a while.
     
  12. sam spade 2

    sam spade 2 Senior Member

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    Don’t post garbage if you haven’t fact checked. :rolleyes:

    As a moderator here, I think your response is a bit harsh.......and insulting.
    Especially when you proceed to do basically the same thing yourself.
     
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  13. Trollbait

    Trollbait It's a D&D thing

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    Car's have had the ability to brake by means other than friction brakes for quite some time. Perhaps longer than they have had brake lights. Then lights may not be working. Or they are two drivers, and the brake lights are always on because of their foot resting on the brake pedal. So drivers should be trained to not rely on the car's lights ahead of them to determine whether they need to slow down or not.

    Having the brake lights come on at acertain level of deceleration is probably a good idea, but it is one that should be applied to all car's, not just plug ins.
     
  14. mr88cet

    mr88cet Senior Member

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    When I do that, I definitely see *a lot* of regen happening. I guess I can’t 100% rule out friction brakes engaging too. My guess would be it’s entirely regen, though.

    I don’t immediately know whether the brake lights light, though; good question.
     
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