Pre-collision alert distance

Prime owner checking in with a story about the "BRAKE!" message on mine this morning. On a two-way backroad with a small truck coming on one side and two joggers running side-by-side (close to the white line) to my right. Well I just continued to drive at 40 mph centered in my lane and straight. "BRAKE!" showed on the display, along with two beeps, 0.3 seconds apart, then the message disappeared, and I passed them. During the message, I just kept my foot lightly on the accelerator. I did not feel any braking pressure.

 

I don't think the car will brake if your foot is on the accelerator - only on brake or not on any pedal.

 

The (EU) Manual says "If the accelerator pedal is being depressed strongly (my emphasis) or the steering wheel is being turned, the system may determine that the driver is taking evasive action".

 

The car will warn you if it thinks you are too close to an obstacle that you might hit. From previous posts I've read here, it won't take action unless/until it thinks something drastic will happen. I've never been in such a situation.

 

I don't know the specific details of the Toyota implementation but in general these systems try to predict whether the car is on a collision path by using the range to the car in front, the relative velocity and the current deceleration.

The distance at which the alert will be given will not be constant and will vary with all these parameters and maybe others such as steering angle, vehicle yaw rate, road temperature.

One paper about a Nissan system stated that the alert was triggered if it would require a deceleration of greater than 0.6g to avoid a collision.

As well as giving the driver an alert the braking system is pre-charged to reduce any delay as well as the sensitivity of the brake pedal being increased as one common problem is that drivers do not brake hard enough in emergency situations.

kevin

 

New Prius owner here, wanted to re-use this thread, as I am experiencing similar concerns as the OP. We just bought a 2020 Prius awd-i, Canadian version with Technology package, but not Advanced. The car is equipped with blind spot detectors, lane departure assist, (both working) and I can only assume it also includes a pre-collision system. I can turn it on and off on the screen, so I assume it is there. But just like the original poster, I am not able to trigger it. We also have a 2017 Acura RDX, and I am getting "BRAKE" warnings on it almost every day. Which I find quite convenient. But with the same style of driving, I am getting no warnings on Prius. Even tried to be more aggressive with approaching cars ahead of me, but nothing happens (I set the sensor distance on MAX). Does anybody else have other car brands which give "BRAKE" warning much further in advance than the Prius? From the videos posted in this thread, it appears that the system will only engage 2-3 meters away from the object (at least with city driving). Our Acura starts flashing about 30 meters away and beeping maybe 15-20 meters away. Which gives enough time to react without any panic because you know that the system works well in advance. I just don't know what to expect with Prius, wish it worked the same way. Any word of assurance would be appreciated.