Accident avoidance report: Prius F

Bob: I have all those bells and whistles on my '13 p-5 -- at the insistence of my non-driving wife who says "you're old and you don't react like you used to!"

I believe the auto-braking is not linked to the cruise as I have had it come on twice -- once with cruise and once without. It gets your attention and reacts faster than I could to a rapidly decreasing distance to an object. My only minor whine is that to confirm the system has started slowing you for a really good reason, one has a tendency to look for a visual confirmation from the instrument cluster where there's a flashing "brake" light and audible signal ... and then look up and react to hitting the brakes yourself. I think I just need to retrain my aging synapses to automatically move my foot to the brake while looking ahead and not at the dash (in case I am distracted by trying to tune the radio).

Eliot

 

Hi Bob,

I have a 2012 Five with the ATP.

The Pre-Collision System (PCS) is always on, and does not require the use of the Radar Guided Cruise Control (DRCC). The system tries to be very un-intrusive, meaning it will wait until it is absolutely certain something bad is about to happen, before doing anything. There are two stages, Stage I will sound the buzzer only, if you do not act, Stage II kicks in and slams the brakes. I have only experienced Stage I, as I am a pretty conservative driver. I will say that the PCS activated mostly for false positives, like a car slowing down to make a turn in front of me. To its defense, it has no way of knowing the object it detected will get out of the way before I get too close.

DRCC, on the other hand, is like PCS on steroids. It will react and adjust the speed for anything moving slower than you, within range. I have had people cut in front of me on the highway while I was distracted, the brake activation definitely grabbed my attention and brought my eyes back on the road. It has saved me a few times on the highway at night.

I just came back from a 2,000 mile road trip. I will report that the DRCC/LKA made the driving experience very relaxing.
Going on a long trip | PriusChat

A little off topic, when I was on my trip I saw a commercial in the hotel for the new Infiniti Q50. It claims to be able to warn you about impeding doom 2 cars ahead. I searched online but still couldn't figure out how it would work.

 

Yeah! saw that too! Interesting! No idea how it works.

 

May be it flies a drone 2 cars ahead? LOL. Too early to cast doubts but I do wonder about the reliability of the said system.

 

Sure another thing to carry in the hatch back, a drone! Now I have a spare tire and a drone in my hatch back!
One problem I can't operate the drone unless I put down my i-phone down first!

 

Among the disappointments, the Toyota Prius v and Infiniti JX.​

Zuby said, "Both of these cars are advertised as having auto-braking systems; in our tests we did not measure hardly any reduction in the speed of the crashes at 12 and 25 miles per hour."

Infiniti officials say they're going to study the results of the tests while Toyota officials say that their Prius v does not have auto-braking technology, and they say that they don't advertise that it does - what they say is their vehicle has a pre-collision system that mitigates the effects of a crash.​

 

PCS is turned off and will remain off until Toyota fixes it. Read the owners manual. I'm too lazy to bring it up and copy the section into this message, but it warns that "certain bridge expansion joints and other things" may trigger the PCS, putting the brakes on hard. This is very dangerous in heavy traffic and I won't have it!

As for DRCC, I use it all the time as you can't turn it off. Most of the time it works but it's irritating as the car will slow for no reason, such as when following a car that is turning right off the road ahead, when you KNOW he will be gone before you get there. Often he pulls onto the shoulder but the system still thinks he's a collision item. The drivers behind get really irritated when that happens. Also a large truck in the next lane will cause the car to slow. I'm happy with it but not impressed. I have to "work around" its' shortcomings.

 

I have the ATP and I have had the pre collision system activate. I was on the freeway going about 70 and the car in front of me came to a full stop. I noticed this and started to apply the brakes then soon realized I wasn't stopping fast enough. Before I could even press the brake any harder the car started beeping, "BRAKE" flashed up on the display, and full brake force was applied, I even felt the ABS working. The seat belts pre-tensioners activated as well. My car came to a stop about 1.5 feet from the car ahead of me and I believe that had I not had the PCS I would have hit that car in front of me. For this reason I will not get another car without a pre-collision system. From what I understand the second you touch the brakes it will apply all the force needed to avoid the accident or mitigate the damages. And If you dont touch the brakes at all it will auto-brake. The IIHS findings surprise me, and I definitely think it's a useful system and deserves more credit!

Page 249 of the manual says "When there is a high possibility of a frontal collision, the system warns the driver using a warning light, warning display and buzzer. If the system determines that a collision is unavoidable, the brakes are automatically applied to reduce the collision speed".

Here is a link to a youtube video with the auto-brake being tested:

 

To be fair, in your case:

1) You noticed the stopped car, and initiated the braking, not the radar.
2) The brake assist feature will apply full braking force, with or without PCS.
3) Since you did not wreck, the seat belt pre-tensioners did nothing.

I am not dogging the system, I think it is useful but you would have done as well without it, in the case you cited.

I have hit the brakes at high speed and then found the brake assist feature detecting a panic stop and appled full force. My PCS did not pick up anything because it was too far away.

 

I have experienced the brake assist feature as well. One time I quickly released the accelerator and slammed on the brakes to avoid hitting a car that cut into my lane. The seat belts retracted and full brake force was applied. The PCS did not activate, no buzzer, no warning. I do know the difference between the 2 systems and I can tell you that the pre-collision system activated in the first instance I explained, the brake assist alone would not have helped me avoid the accident. You are right, the radar didn't initiate the braking, but it knew that I wasn't stopping fast enough and gave full force. Like I said, I was already on the brakes and just as I realized I wasn't stopping fast enough, it started beeping and before I knew it I was stopped without pressing the brake any harder. I would have hit that car ahead of me if I didn't have PCS. Toyota's System is not as good as other systems in that you need to press the brakes to avoid the accident, and it can't fully auto brake and avoid an accident like Volvo. The IIHS makes it seem like it does nothing to help but I believe it does... just my 2¢

 

The lawyers wrote that part of the manual. I've never had the PCS activate for anything other than a car in front of me. I know that there are some problem spots/vehicles, however. You'll still get the warnings and seat belt tightening, so you can at least know if you ever get a false alarm - it just won't apply the brakes for you. Maybe if you drive enough miles without any false alarms, you'll trust it?

You can turn DRCC off if you like; the manual says to turn cruise on with the button, then turn it off, and then push the cruise lever away from you for 1 second. The manual also says you can't switch if you've already used DRCC, and you can't switch back to DRCC - you have to power cycle the car.

Other than that, I agree; it brakes in many cases that a human wouldn't have to. It also accelerates in some cases where a human wouldn't; for example, following somebody at their speed (but less than the set speed), if somebody cuts in between and is moving faster, and then they move into a different lane again, the car can accelerate to follow the faster car, until it sees that you're still behind the slow car.

There are two distinct systems; the brake assist as you note, and the pre-collision brake assist as BrianPB describes. The pre-collision brake assist works when you've applied the brakes and you're approaching something at >18 mph. The effect is similar; the computer applies the brakes harder than you're asking it to.

And you're right - the pretensioners did nothing, since those are based on a pyrotechnic charge to retract the seat belts immediately following an impact; however, I'm sure he was referring to the pre-collision seat belts. These are motorized, and apply in anticipation of a possible impact, so that if there is an impact, the pretensioners are more effective (there's less slack to take up).

I've had the audiovisual warnings a couple of times, and maybe the pre-collision brake assist once. I stopped the car VERY quickly, I just don't know for sure if the computer helped make that possible - it was howling at me to BRAKE! the whole time, at the very least.

 

Incorrect. You simply have to turn off the CC to cancel DRCC. When you turn CC on but before you set speed, push the lever for 2 sec to engage normal CC. Once speed has been set you can not longer switch back and forth between modes.

 

When I was shopping to a Prius four year ago, this is how I remember the ATP being advertised -- as reducing collision severity, not providing collision prevention. The later function was still entirely up to the driver.

That is why I'm disappointed the Prius is given a failing score, when it wasn't intended or advertised to meet this standard in the first place. Did I miss some advertising claims since then?

(Note: I didn't buy a model with this feature.)

 

That's just what the manual says. Personally, I have no reason to use plain cruise control - I paid for DRCC, so I'm using it, dammit!