Opinion RE One Pedal Driving

[Craigins]

There must be some downside. I just haven't figured out what it is yet. Every trade is just that, a trade.

Washington Beltway. Only 97% of the time. Close enough?

Moving your foot takes time. That time can be the difference between an accident and stopping in time.


So there are a 4 phases:

Phase 0: Cruising along happily maintaining 60 mph

Phase 1: Idiot cuts you off so you immediately take foot off skinny pedal. TIme required to do that in Lexus: X milliseconds. Time to do that in Rivian: X millseconds

Phase 2:Move foot to fat pedal, Time required in Lexus: Y milliseconds. Time required in Rivain: Y milliseconds. Thrust during these Y millisconds in Lexus: 0. Thrust on Rivian in these Y millisconds: - T. Energy absorbed from Lexus in this time 0. Energy absorbed from Rivian in this time: -T*Y*v (v is velocity).

Phase 4: Hit fat pedal.

I dunno. That's what I am trying to find out. It seems to me that it takes just as long to move my foot from one pedal to the other irrespective of whether regen is on or not AND when phase 4 begins I have, with regen on, already removed energy from the car but with it off I haven't AND during phase 4 I have thrust from the friction brake augmented by the thrust from regen. Why am I worse off with regen.

Your issue is you are not looking into the future when driving, you are reacting to the immediate surroundings.

In your example, I would have noted the drivers behavior from the review mirror. As he approaches me, I pre-emptively remove my foot from the skinny pedal and place it on the wide pedal.

Then if he cuts in front and has to slam on the brakes i am in a much better position than you are.

Defensive driving vs just reacting.

Everyone drives differently, but because we do not drive exactly like you do, and we point out a deficiency of OPD in the style we drive.

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[Craigins]

The best thing about regen braking is that combined with regular brakes + regen braking = greater stopping force than traditional brakes alone. In other words, greater deceleration to change speed.

Regen + friction brakes = more stopping power.

However that has nothing to do with OPD. Regen could be tied to the wide pedal.

 

[SmorOfNaivir]

Edit: I made a graphic
https://docs.google.com/presentation/d/1sRhdlnBxoErxEzpaKW5B7DQ_SJ6ls3LImPrtFKaMYjQ/edit?usp=sharing

*brake

*braking

 

[mkg3]

Regen + friction brakes = more stopping power.

However that has nothing to do with OPD. Regen could be tied to the wide pedal.

Correct and agreed. That's why I'd said the best thing about regen braking, and not OPD.

 

[Craigins]

*brake

*braking

thanks, in a rush trying to finish it before a meeting, missed one a copy/pasted throughout the whole thing (except the last slide lol)

 

[shamoo]

So couple of thoughts about the statement.

1) covering the brake only apply when coasting and when on track, one is either accelerating, even throttling (whatever the EV equivalent term is) or braking. It is rare that the driver is coasting and,

2) Do you not use left-foot braking? Many drivers use both feet, especially with a clutch pedal disappearing in favor for double clutched paddle shifters.

The best thing about regen braking is that combined with regular brakes + regen braking = greater stopping force than traditional brakes alone. In other words, greater deceleration to change speed.

Of course the mfg know this so some are regressing and relying on regen to carry heavier load for stopping, such as VW ID.3, 4, Buzz..... They all have DRUM brakes in the rear instead of discs.

I figured I'd get some comments about #1 . Yes you're right. If you aren't braking or accelerating, you aren't optimizing your racing. On public roads I obviously can't do that, so I cover the brake more.

I don't use left foot braking actually. I tried it on track before and I just wasn't a fan. I used to do basic track instruction and if someone really wanted to learn it, I'd recommend another instructor. For HPDE, I'd tell them go to ahead and I could talk them through it, but I wasn't good at it myself.

 

[Singletracker]

I’m a big believer in driving smoothly and planning ahead. I tend to drive significantly quicker than most in the mountains, but still believe in being smooth, maintaining momentum, not necessarily racing from corner to corner, only to slam on the brakes. There‘s nothing like getting a good rhythm going on a mountain road. It drives me crazy following people who are constantly on the brakes and changing speed and pace, either because of poor planning or just ineptness, who then end up causing a herky jerky ride for everybody. You know the ones - they are the drivers that see the slow to 50 MPH sign for a corner and hit the brakes, even though they were barely doing 45 as they approach the corner - jeez. These are usually the slowest drivers on the road, BTW. Oh, yeah, you can also throw in all the tailgaters out there, who need to be constantly on the brakes. I sometimes wonder how often these idiots have to get a brake job.

Sorry for the rant. Just had a frustrating drive over Hwy 50 in the Sierras (Great drive with no traffic, but….) Having said that, my point is, I suspect drivers, who drive constantly riding or hitting the brakes, will have a harder time adjusting to OPD. Personally, I look forward to it. It sounds cool!

 

[ajdelange]

Your issue is you are not looking into the future when driving, you are reacting to the immediate surroundings.

Oh yes indeed you are! Or you had better be. Your brain uses an algorithm called a "Kalman Filter" to predict where you and all the threats are going to be and prescribe control inputs to put you where you would like to be. It uses a model of how cars move. "Tuning" the filter involves getting that model to reflect your driving conditions such that the parameters are different for the Beltway than they are in a rural area, for example. I am particularly aware of the aptness of this analogy because my wife's Kalman filter is not present or poorly tuned.

In your example, I would have noted the drivers behavior from the review mirror. As he approaches me, I pre-emptively remove my foot from the skinny pedal and place it on the wide pedal.

Then if he cuts in front and has to slam on the brakes i am in a much better position than you are.

Are you? Were I to do what you propose I'd slam on the brakes and get rear ended. Far safer, I'd say, to use regen and get the immediate, if not so dramatic slowing that comes from regen rather than slamming on the brake. In any case for this particular scenario my foot is over the brake at all times via Tesla's collision avoidance system. I wonder if it considers what's behind when it slams on the brakes. What does RIvian's system look like?

 

[Ripped]

Like I said in the other post, I am probably in the minority here, (Hyundai EV) being okay with the one pedal high level of regen for city driving in traffic.

When I back off the accelerator pedal slightly the regen does not kick in so hard.

Buy if Hyundai can have a 4 level setting for Regen 0 to 3, then I'm sure this could be easily software configurable for Rivian. Majority of people seem to like the idea.

When I get my R1T, I would like it for trailer towing with surge bakes as I usually pulse the vehicle brakes during long downhill stretches. Zero regen setting might help with that, or having the steering wheel paddles and cycle the regen on and off for pseudo-braking.

 

[timesinks]

Your issue is you are not looking into the future when driving, you are reacting to the immediate surroundings.

In your example, I would have noted the drivers behavior from the review mirror. As he approaches me, I pre-emptively remove my foot from the skinny pedal and place it on the wide pedal.

Then if he cuts in front and has to slam on the brakes i am in a much better position than you are.

Defensive driving vs just reacting.

Everyone drives differently, but because we do not drive exactly like you do, and we point out a deficiency of OPD in the style we drive.

The way I deal with this using OPD is to ever so slightly ease off the accelerator. "Coasting" is a misnomer because it doesn't mean holding a steady speed. When coasting, you are giving up speed to wind friction and rolling resistance. When I'm driving an EV, in these situations, I start easing up the throttle to slow in a manner that is similar to the speed I'd shed from "coasting". If I need to react, complete throttle lift results in significant and immediate further reduction in speed while my foot finds its way to the brake pedal.

In manual ICE vehicles, I would often down shift in these scenarios to increase the engine braking effect in the event of a panic stop rather than coast in a higher gear with my foot over the brake. I was definitely taught cover braking and have used it, but I found it most appropriate for ICE vehicles with automatic transmissions.

In general, the best way to be ready to stop is to actually slow down -- that will meaningfully shorten the stopping distance.

 

[ajdelange]

Buy if Hyundai can have a 4 level setting for Regen 0 to 3, then I'm sure this could be easily software configurable for Rivian. Majority of people seem to like the idea.

I've changed the poll to indicate choice of the number of levels of regen you think appropriate. Please go back and add your vote for that (you'll have to hit "Change Vote")

 

[Nermal]

I didn't see option for "R1T is my first EV and I love OPD in high regen during my short time with it but have nothing to compare it to" ?

The analysis going into this is fascinating. For me I always just thought of it as very strong version of backing off an ICE manual - if I don't think that's going to do it, I go for the brake. For that matter, the truck might have already made that decision with its own emergency braking algo. I guess that's part of the discussion in that backing off the right pedal implies hard braking before you even get to the brake pedal.

What would we all think of a way to engage the hold/parking/emergency brake on the move if OPD and brake pedal fail us a la the old handle between the seats? Might be an aftermarket opportunity for a dummy handle in the under dash storage area to serve as a security blanket. Totally joking on this paragraph.

 

[Bullitt]

OPD works great! To each their own, but this will be my 29th car/truck I’ve owned and its amazing as an enthusiast driving in canyons and also in stop and go traffic every day that I commute in.

 

[ajdelange]

What would we all think of a way to engage the hold/parking/emergency brake on the move if OPD and brake pedal fail us a la the old handle between the seats?

If you put the vehicle in P an auxilliary brake is engaged. Of course you don't do that at speed but I guess software could be re-wickered so that if you did that could be interpreted as an "emergency stop signal" which would, checking behind and forward, apply the brakes as fully as could be done without collision at either end. But I think the current emergency auto braking algorithms are deemed safe enough. Remember that there will be some situations where there is simply nothing you can do,

 

[RexRemus]

So couple of thoughts about the statement.

1) covering the brake only apply when coasting and when on track, one is either accelerating, even throttling (whatever the EV equivalent term is) or braking. It is rare that the driver is coasting and,

2) Do you not use left-foot braking? Many drivers use both feet, especially with a clutch pedal disappearing in favor for double clutched paddle shifters.

The best thing about regen braking is that combined with regular brakes + regen braking = greater stopping force than traditional brakes alone. In other words, greater deceleration to change speed.

Of course the mfg know this so some are regressing and relying on regen to carry heavier load for stopping, such as VW ID.3, 4, Buzz..... They all have DRUM brakes in the rear instead of discs.

On point #2 - "greater stopping force than traditional brakes alone" - that's not really true. Any modern vehicle is equipped with brakes that can exceed the grip of the tires - we wouldn't need/have anti-lock braking systems if the brakes were not capable of "locking up" the wheels (braking force exceeding the grip available at the wheel). Regen isn't some magical thing that lets you somehow "brake harder" than just traditional calipers and rotors - braking force is ultimately limited by grip at the tire.

Regen braking, as some others have stated, will take effect "sooner" than purely traditional braking - in an emergency stop with a traditional vehicle, you lift off the gas and coast and there is a delay before you can move your foot to the brake pedal and really start to decelerate (this assumes 1 foot driving as I think the vast majority of people do). In a vehicle with regen, especially strong regen like the R1x, as soon as you lift off the accelerator you are starting to decelerate fairly aggressively in the time your foot moves between gas and brake pedal. So you may see an improvement in "stopping distance" but it's not from a magical increase in braking force, it's in cutting out the reaction time delay before (moderately) aggressive braking begins.

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