Will DRCC Cruise Control or Front Collision prevention completely stop the car?

Discussion in 'Prime Main Forum (2017-Current)' started by ride43, Nov 18, 2017.

  1. ride43

    ride43 New Member

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    I have some questions about DRCC. Sorry for the long post.

    From what I read in the owner's manual it says that it may not stop the car. Of course we should be prepared that it might fail, but does that mean it generally does not try to stop the car fully and you always have to brake to a complete stop manually?

    Then lastly will front collision warning stop the car completely if there is sufficient time? Again it says it may not work, but will it try? The sales rep said it will help slow the car and warn you, but that you have to stop it yourself. These seems like good practice, but it would be nice to know if the car would actually be able to stop itself if the driver was slow to react'.

    The reason I ask is I tried out DRCC on the highway and there were some sections where speeds dropped from 70 to 15, 60 to 10, and then to stopped. It handled all of the slowdowns and accelerations just fine except when the car in front came to a full stop. The red light started blinking and beeping, and I jumped on the brakes to stop and came real close to making contact with the lead car. I wasn't sure if the DRCC would have stopped it all the way had I not hit the brakes.

    Another thing to note: If I was driving myself I would have slowed much earlier so it wouldn't have been as an abrupt stop. I got nervous the guy behind might hit me as the DRCC was braking so fast.

    What do you guys think about DRCC when traffic is coming to a strop? I imagine I should cancel Cruise control well before it gets close to stopping from fast speeds. While at lower speeds in bumper to bumper traffic it should have plenty of time to stop so I can leave it engaged, and react if needed manually later.
     
    #1 ride43, Nov 18, 2017
    Last edited: Nov 18, 2017
  2. bwilson4web

    bwilson4web BMW i3 and Model 3

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    My impression, not yet measured, is the relative speed difference determines if the car will come to a stop on its own:
    • ordinary stop and go traffic - DRCC will come to a complete stop with a full car length behind the lead vehicle. No fuss, no bother.
    • coming on to stopped traffic at speeds of ~40 mph - DRCC will detect the stopped car but won't aggressively brake to avoid the collision. It will alert before the impact. Manual braking is strongly encouraged.
    Bob Wilson
     
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  3. SteveMucc

    SteveMucc Active Member

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    I use it regularly in stop & go traffic in traffic going through the Lincoln tunnel into nyc. works great. slows, stops, and if it traffic moves quick enough will pick up and start driving otherwise you have to tickle the stick to get it going again. I imagine that if I was coming up upon stopped traffic from high speeds that I would slow the car down manually. sometimes I pays to be a human with built-in sensor fusion.
     
  4. Andyprius1

    Andyprius1 Senior Member

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    Yes, it will totally stop the car
     
  5. ride43

    ride43 New Member

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    Excellent. Thank you for the responses that totally makes sense.
     
  6. fuzzy1

    fuzzy1 Senior Member

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    Please remember that this is not yet a self-driving car. Those are still at least three years away. Today's consumer-market driver assist features are getting much better, but are still several rating levels short of the accuracy and reliability required for hands- and feet-off driving.

    Don't depend on this feature stopping the car. If you do, then when (not if) it fails to stop in time, if you survive and anyone else is injured or killed, expect very harsh penalties for (at least) gross or criminal negligence for willful improper driving. A murder charge is not out of the question, though criminally negligent homicide is more likely.

    Always be ready to steer and stop the car completely manually.
    As well you should. This is yet another clue that you must keep control, because the current assist system is not yet good enough to handle everything by itself.

    There are systems that can do this, but they are still neither affordable to, nor certified for, the regular consumer market.
     
    #6 fuzzy1, Nov 19, 2017
    Last edited: Nov 19, 2017
  7. pilotgrrl

    pilotgrrl Senior Member

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    There is a thread here where someone posted a video testing the forward and rear collision control systems at low speed using a cardboard box.

    Yes, it worked. Although I don't own a Prime, I wouldn't try - or recommend trying - it on a highway.

    Toyota doesn't, to cover their corporate derriere. It's not meant to take your place, it's meant to augment.

    Posted via the PriusChat mobile app.
     
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  8. Since2002

    Since2002 Senior Lurker

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    First of all I'm glad to see from your comments that you already know that you aren't supposed to fully rely on DRCC, and that you are just trying to understand more about what to expect from its operation.

    You didn't mention it so I guess we can assume that you didn't change the vehicle-to-vehicle distance setting from the default of "long". There is a DRCC button on the steering wheel and if you press it then it cycles through long, medium and short, if you had changed it to medium or short this will make the DRCC more aggressive. Each time you start the car it defaults to long.

    Yes, just like you would with regular cruise control. DRCC is really only good at following the vehicle in front of you, making for a more relaxing, less fatiguing drive either on the highway or in stop and go traffic since you don't have to constantly adjust your speed. But when you can see that things are coming to a full stop ahead of you that is when you should take over immediately and not wait for DRCC to react.

    This is also the case if you are not following anyone at the moment but there is a car say a few hundred yards ahead of you going slower than you are so you will soon be overtaking them. If you are approaching them with a closing speed of say 5mph then DRCC should handle things pretty smoothly. However if they are going a lot slower than you are then you should cancel DRCC and do the approach manually, then once behind them you can resume DRCC.

    Another situation is when a car cuts in front of you. Generally you will see that coming several seconds before DRCC does, so the moment that you see someone cutting in front of you cancel DRCC immediately and back off the throttle until they are in your lane at a safe distance then you can resume DRCC. I'm referring to when someone pulls into your lane in front of you at a very close distance. If they change into your lane ahead of you at a safe distance and just slightly slower speed then DRCC should be able to handle that smoothly.

    Also whenever possible be sure to cancel DRCC by pulling on the lever and not by tapping the brake pedal. Tapping on the brake will flash your brake lights which will cause the driver behind you to react abruptly since he doesn't know if maybe you are slamming on your brakes to avoid something.
     
  9. Db17

    Db17 Member

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    I’ve wanted to try a find a empty parking lot and do a 40 mph into a big refrigerator cardboard box test. I’ve just never found the time or the box :)
     
  10. A Prime Factor

    A Prime Factor Formerly "I want my PHEV"

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    Today I had the experience of driving on the highway at 65 mph using (regular) cruise control and there was an object that looked like a ladder lying across the lane I was in. I guess it had fallen off someone's truck. There was no time to stop by the time I noticed it, so I had to swerve into the next lane. Good thing I was paying attention and good thing nobody was in the other lane.
     
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  11. Tideland Prius

    Tideland Prius Moderator of the North
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    This might help you understand the situation. It has both rapid reduction in speed and coming to a complete stop from 50km/h (31mph). Note that it avoided the pedestrian at 40km/h and 60km/h but not at 45km/h (weird, right?). This is why there's the disclaimer of "it may not completely stop in all situations". You can see it hesitated in the 45km/h test.



    Toyota designed TSS-P to completely avoid a pedestrian collision up to 19mph (30km/h) and a vehicle collision up to 25mph (40km/h). Anything higher is a bonus (in terms of completely avoiding a collision). Otherwise, it will, at the minimum, reduce the speed of impact, thus reducing the likelihood of sustaining injuries. (Basically, it was designed to pass the IIHS' 25mph "high speed autobrake" test)

    As for DRCC, I will usually change to the max 3 bars if I see cars slowing down to get the car to lock in and slow down earlier. Otherwise, I'll cancel cruise and glide/coast down and once I'm comfortable with the distance to the car ahead and the rate of deceleration, I can push RES and it will lock onto the car and slow down with it or follow it.
     
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