Today driving through snow at 25-30 MPH, reached to put Prius in B mode to slow down at stop light. Some reason my hand punched the PARK button instead, and Prius just shifted into neutral. Puzzeled why no braking action and when I saw where my hand was, I was so glad the computer was smarter than me and didn't actually engage the parking gear/cam/detent (whatever the device is that locks up the transmission, sorry not mechanically conversant like you members ). Just a comment.
BTW, there is no benefit in using B on snow. On RWD cars, shifting to Low can add drag to the rear of the vehicle, so you do not swap ends. The Prius is FWD, so using B is only adding drag to the front, making it more likely to swap ends. If the Prius had a handbrake, this would be a good time to use it. they almost always add drag to the rear wheels.
I've seen a buddy back in high school force his Buick into park while driving and it just instantly shears the pin off and renders park useless (while making a loud grinding noise)
Thats what I envisioned if I ever accidently punched park while moving. Glad the Prius computer saved my a**, not to mention my wallet
Depends on how hard you pull on the e-brake on a FWD car with a rear e-brake. It's fun to take any FWD car into an empty slippery parking lot, pull the parking brake so the rear tires lock up, and do 180's. Once the rear tires lock up, physics take over, and the lower co-efficient of friction of the now-sliding-rear-tires means they pass up the front ones. In general, brake line "proportioning valves" (especially vehicles that tow/haul) are designed to put more braking power to the front. That way, if the front tires lock up but the rear's don't, you still continue sliding facing forwards (but you just can't turn).
Pressing on the brake also applies drag only to the front, assuming regenerative braking is in effect. You have that issue either way. That said, don't bother with B mode for normal slowing. It's not really useful: you waste gas, don't slow down any better, and don't show brake lights while slowing. Save B mode for the mountains where it works well. Tom
I beg to differ on that. Although the majority of vehicle braking is through the front wheels, when the brake pedal is pressed all four wheel brakes are activated - regenerative braking aside. During our recent snowy conditions (which have now thankfully thawed out), whenever I was approaching a steepish decline covered in snow and ice, I slowed to about 25kph and engaged the B mode. The effect was amazing. With feet off the pedals the car would slow to about 20kph and would maintain that speed while decending the hill. Trying to control the same decent in D and feathering the brakes was not as 'comfortable' as using B mode. True, it doesn't show the brake lights, but niether does any other automatic car placed in it's lower gears. As for wasting fuel, that's not really an issue when trying to complete a journey safely.
I will have to agree with Chippy on something--this is why I often prefer downshifting (especially on a manual transmission which offers greater control), rather than stepping on the brakes to slow a vehicle in slippery conditions. If the roads are slick, the worst that will happen when stepping on the brakes is the wheels can obviously lock up. Conversely, when downshifting (manual, auto, etc....), the wheels will simply spin at a slower speed and NOT lock up. To me, that's safer than full lockup. If I have a manual transmission, and it's slick out, I often don't even touch the brakes until the very last few feet of stopping (this includes going downhill). This is where 4WD really has it's advantages over FWD or RWD, since all 4 wheels are slowed down during downshifting, rather than just 2. If simply stepping on the brakes, the vehicle doesn't care if it's 2wd or 4wd, as that become irrelevant during braking. From my experience, at least in certain situations, I can often slow a 2wd vehicle more safely by downshifting rather than stepping on the brakes.
