[Quietcars] Does anyone on list know about this and which carrier are they referring to?

[Robert Wilson]

This is a user report of the Prius accident avoidance system in operation. In this case, a false positive:

* * BEGIN USER REPORT * *

The pre-collision system in my new 2010 Prius activated on my way to work this morning. The road was straight, I was not approaching any obstacle, and there was no other car as far as I could see in the lane ahead of me. I'm just driving along and all of a sudden the beeper sounds, the seatbelts tighten, and the car slams on its brakes hard enough to make the tires squeal (it all happened very quickly, but I clearly recall the sound of the tires screeching). Very shortly afterwards the system apparently realized it was a false alarm and everything went back to normal. I think the whole incident took less than one second from start to end.

I can think of some reasons why this might have happened, and would welcome other ideas:

    * The radar unit or computer is faulty. I.e. this was just a complete and total malfunction. Seems pretty unlikely.
    * I was driving through moderate low-level fog at the time. Not enough to prevent me from seeing quite a distance ahead of me, but I was driving through the occasional white wisp of fog. Perhaps the rader got a hit from a bit of fog. This also seems pretty unlikely.
    * I think the most likely reason is that the slope of the road changes at the exact point where I was when this happened. I was traveling southbound on the Golden Gate Bridge at the time, and I had just entered the northern end of the bridge. Here is a picture that should give you a pretty good idea of what the road does at that location. You can click on the picture to get a high-resolution view. This picture faces south, so the cars going away from you are going the way that I was at the time. I was at about the same location as the dark red Honda Civic that you can see the back of, in the third-from-the-right lane, just to the left of the green VW Bug. I think that the PCS saw the change in road slope as an approaching obstacle, and then cancelled the alert as soon as I actually entered the upslope. This does meet one of the criteria described on page 252 of the owner's manual, as a condition that can trigger the system, an "uneven road surface", but keep in mind that the change in slope is not nearly as pronounced as it seems to be in the picture. In real life you don't really notice the change in slope while driving over it.

Some random thoughts I've had about this are:

    * The system is quite fast and aggressive. I had read a lot about it in the manual and here on PC, but there is no substitute for actually experiencing it. The beeper, seatbelts, and brakes all activated simultaneously, and the braking and seatbelt tightening were very forceful. I have no doubt that this system could save you from rear-ending someone.
    * If someone had been close behind me this morning, it is highly likely that they would have rear-ended me. My car braked hard, with no warning, on a completely clear road, which would have been completely unexpected for the driver behind (yes, I know people shouldn't be following so closely, but sometimes they do).
    * I need to weigh the likelihood of false positives vs. times when I might actually need the system. If my car spontaneously brakes hard in the middle of the freeway once every year or two, that seems to put me at a lot more risk than that of my rear-ending someone by mistake.

* * STOPPING USER REPORT HERE * * 

There followed a discussion of disabling the automatic brake part so the system still notifies the driver who either brakes the car or steers to avoid the accident. Regardless, it shows the automatic detection of an impending collision and computer speed, activation that works at any vehicle speed. Higher impact speeds are the deadliest and these accident prevention systems handle all speed ranges, not just slow speeds.

I for one think this is the best approach for reducing accidents both car-to-car and car-to-pedestrian. It puts a never tiring, unblinking, never distracted radar and computer on the job of looking for and avoiding accidents. It even works if someone steps off the curb into the path of a Prius (or SAAB or BMW) that can not be heard because of the surrounding traffic.

Bob Wilson

 		 	   		  
_________________________________________________________________
Lauren found her dream laptop. Find the PC that’s right for you.
http://www.microsoft.com/windows/choosepc/?ocid=ftp_val_wl_290