amphipri0n

Was looking through the manual and read this line about one of the functions of the PCS,

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

My question is why did Lexus design the system so that it doesn't apply brakes until the collision is unavoidable? I'd be fine with the system slamming on it if it thinks it can avoid a crash by doing so...

uicandrew

if it was more sensitive, i can imagine a lot of false positives in stop and go traffic in the cities, where you're (depending on how you drive) constantly pressing on the accelerator to prevent other people from cutting in and pressing on the brake because traffic comes to a standstill.

who is to say a younger driver's faster reflexes shouldn't override a more "conservative" collision system?

UTAS

I haven't experienced the PCS yet, however, it seems the sensor is the same one as used in the dynamic radar cruise control (DRCC). PCS works the same way, except it is almost instantaneous and close in range of another vehicle. As the disclaimers suggest, PCS is not intended as a auto-pilot device - audibles before a collision will most likely not be useful - but it will awaken you from that texting device in your lap just before the crash.

As for DRCC, which is related somewhat to PCS, I prefer cruise control on manual, without DRCC engaged (disengage DRCC by pushing the lever forward and holding a couple seconds). Here's why:

When DRCC is engaged, the audible will sound almost simultaneously with the automatic braking, when the distance is much closer than the set range; this happens with other cars frequently changing lanes, or in merging traffic. With DRCC engaged and when a car in front is too close, one loses acceleration, until disengaging the cruise by either stepping on the brake (which is already happening) or by manually disengaging cruise control. To me, it's a little disturbing. As mentioned, DRCC also recognizes other cars cutting in front, and suddenly the car forces deceleration - it wakes everyone up.

In rain, snow, or sleet, PCS and DRCC are not of much use, because the sensor(s) are obstructed with droplets of precipitation. Of course, it's not advisable to engage cruise control during inclement weather.

Leave the PCS on, but be aware of its capabilities and shortcomings. And don't text while driving.