PCS question

A few days ago, my pre-collision warning beeped and flashed when a car unexpectedly pulled in front of me from the side of the road. I didn't feel the brake pump up and still had sufficient time to avoid a crash. I believe there are a few thresholds for the pre-collision system and this must have been the least aggressive.

 

I welcome anyone to test out the threshold....

 

I don't have PCS, but my understanding is that once PCS activates, computer determined that the object ahead and your Prius will engage an unavoidable collision; i.e. brake boost goes to standby/ready, seatbelts tighten, etc. I think the "between the lines" emphasis is unavoidable. Sounds to me like you would have a collision. I don't think you could engage the brakes as fast as computer.

If you engage the brakes just before the warning indicators, then I suppose you would avoid the collision since you did this before PCS activates.

I suppose the PCS system program assumption is that your Prius and the object ahead maintain their current course of collision. If the other object/vehicle veers, speeds up or alters course, then maybe collision is avoided.

This safety option sounds very practical.

 

Dear op I disagree with what twittel "thought" how pcs works.
I did a lot of my own research with my car (having pcs ofcourse)
1. Pcs works in 3 stages. 1st one is warning, second is brake prep/optimization and 3rd is applying brakes and cinching the belts.
2. Of all the experiments I did mentioned in the post link below, I could never reach stage 3 because it was too risky for me. I always ended applying brakes at the end because collision was obvious.
The belts never cinched for me even when I applied brakes in these emergency situations. My last experiment scared the daylights out of me because the guy's car in front of me stopped and I was closing in on him at 23 mph. Only around 10 feet were left between us when pcs was already shouting loud. At that time i tapped the brakes and the tires screamed. If I had not nudged the car towards left, I would have hit the guy's car for sure. but I must say that the brakes performed 3 times more powerful than the force that I had tapped the brake with.(clearly proving to me that the pcs "primed" the brakes for me in less than a second !) also keep in mind that the tires on a v package are quite wide so that's like twice the stopping force compared to regular Prius tires. So my cars tires will never scream like Crazy but if I ever break that hard, I know I will only hear a light "slurrpp" kind of noise.
Also in the video on YouTube with the cardboard boxes, the guy slammed twice in the boxes because the pcs did not provide enough brake force.
So it's better for you to tap the brakes yourself if you wish to avoid collision.
Here's a link to our old posts
http://priuschat.com/forums/showthread.php?t=69375

 

Chris, thanks for the practical update on PCS. I'm almost hearing you say that PCS is not as responsive as I assume, but it still seems to be a great safety option.

Though PCS is passive, does it work if dynamic radar cruise is turned off? I assume it does.

 

PCS is on all the time. I think that there is a button buried underneath the dash that can turn it off. I guess that this OFF button is good for those who autocross. I have heard PCS activating when people do slalom testing and come close to cones.

Stage 3 or whatever it is called of PCS is to decrease the severity of the accident, not to avoid it completely.

 

I braked aggressively as the other car accelerated away. One of the PCS features is to prepare (pump-up) the brakes for a panic stop. I did not encounter this increased braking action, which was unnecessary.

 

I had my PCS activate for the first time this morning on my way into work. I commute on a pretty crowded road and it is a lot of stop and go. I was a little jet lagged this mornig and was not paying as much attention as I should have been. I believe I was going about 30 when I heard the warning beeps, instintively, I slammed on the brakes and I noticed that they seemed to engage really fast. I also realized that my seat belt cinched up for a second or two. Anyway, I did not hit the car in front of me but it was fairly close (5 to 7 feet?). I did hear the tires squeal a little as well during braking. Cruise control was off the whole time during this, so its good to know that PCS is paying attention all the time (even if I'm not!)

Chris

 

the problem with the aluminum foil is that they setup it up too high. It should be on the ground like the boxes.

 

so.. you saw the video with the foil? wasn't that one only with foil? there is one with boxes.. and a few others floating around. the guy with boxes holds the accelerator the entire time and the car almost stops him at the boxes. if he would have touched the brake, he would have stopped.. it was obvious on each run.