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the bigger problem is that brake pedal application is read by some sort of switch or sensor, and when it fails the car will be undriveable.

...or how about the additional degree of freedom (at least one, perhaps more) that is introduced into that system as you allude to. If the failure of the sensor/switch leads to zero throttle, "interesting" outcomes become probable.

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Current stable:
2019 BMW M2 Competition slicktop 6MT
2011 BMW M3 sedan slicktop 6MT
2007 BMW 328i wagon (slushbox for now)
1975 CanAm 125MX2

That's just it...all these failure modes will have to be considered and the software written to accommodate, too. My guess is a failure of the switch is pretty easy to detect and allow the car to keep working, albeit with a CEL as well as no system now in place to detect improper pedal application.

It is a lot of work and a lot of money spent that will save fewer lives than legislating all our cars be neon colors. Not worth it, IMHO.


--Donnie

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My Blog

Am I missing something? I skimmed the document up to page 18 and found some encouraging statements that appear to make this completely a "non issue" for enthusiasts and for cost except for the few remaining mechanical throttle systems which NHSTA expect will convert to ETC soon. What new cars still have mechanical throttles?

Page 8:

"Based on compliance information that NHTSA receives from vehicle manufacturers annually, almost all model year 2012 light vehicles sold in the U.S. will have a BTO system. Based on our experience with these BTO systems, we believe they will comply with this proposed rule without significant modification. Consequently, any manufacturer design, validation, and implementation costs associated with this proposal should be minimal. Furthermore, compliance testing costs are expected to be low since the proposed test procedure is nearly identical to existing brake performance test procedures. Tests could be conducted along with existing brake performance tests."

Also on page 16:

"return after the driver stops pressing on it, BTO will engage as soon as the driver applies the brake pedal (there may be a delay built into the system on the order of one second; in some systems, other pre-conditions have to be met for the BTO to engage, as discussed below)."

Further down page 16:

"Some manufacturers’ implementation of a BTO system may include checking for certain prerequisite conditions prior to actuation. The BTO system may check conditions such as vehicle speed, engine revolutions per minute (RPM), brake pedal travel, and pedal sequence (i.e., whether the brake was pressed first and then the gas pedal, or vice versa) to determine if the driver’s intention is to stop the vehicle. Based on these conditions, the BTO system may determine that the combined brake and gas pedal inputs are actually intentional, and it would not

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necessarily intervene in that case. This may occur, for example, if the vehicle is at very low speed and the driver presses on the brake first and then on the accelerator. This behavior is consistent with intentional driving maneuvers which may be used for such things as trailer positioning or similar situations. We believe there is no particular safety issue in these situations, and in fact this type of “two-footed” driving capability can be desirable and may be in widespread use. Since there is no reason for the BTO to intervene in this case, today’s proposal would not prohibit this kind of BTO design. In fact, our proposal intentionally avoids restricting the specific design aspects of BTO systems so that current BTO systems can be accommodated to the greatest extent possible, because we believe those systems (based on our testing) would address the safety issue at hand."


Is there something "nasty" I missed?

Dick

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Dick Rasmussen

FS 50 2018 Mustang GT

I think what's an issue with enthusiasts is for those who use left foot braking at speed with both brake and throttle modulation attempted at the same time. I use a ton of this on places like VIR south course in the bitch turn and also at the bottom of hill left. In autocrossing I make extensive use of left foot braking to get nice smooth transitions and also to get just the right weight transfer I want at some points. With a throttle cutout, all of that type of advanced car control is eliminated.

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Current stable:
2019 BMW M2 Competition slicktop 6MT
2011 BMW M3 sedan slicktop 6MT
2007 BMW 328i wagon (slushbox for now)
1975 CanAm 125MX2

Maybe in cars with some kind of performance suspension mode (like the Corvette's Active Handling) this "feature" will be disabled when you take off the nanny

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1990 Faded Reddish CSP Lite Miata
2002 Electron Blue Corvette Z06
2005 Mazda 6 Wagon
2003 Nissan Pathfinder DTV (Dog Transport Vehicle)

Let''s hope. Perhaps when fully disabling DSC/PASM/whatever (for cars that will still allow such), the brake/throttle cutout will be disabled too...good point.

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Current stable:
2019 BMW M2 Competition slicktop 6MT
2011 BMW M3 sedan slicktop 6MT
2007 BMW 328i wagon (slushbox for now)
1975 CanAm 125MX2

I can see your concern Chuck. Hopefully the cars that would be used this way will be able to turn BTO off just like most performance cars can turn off the current "nannys".

I haven't done enough open track to experiment with simultaneous gas/brake (except for heel/toe for open track and street downshifts). When I opened tracked my 88 Mustang there was no way I was going to put any more heat into those brakes than absolutely necessary. The one time with the 2001 at VIR south was the same except I still had brakes at the end of the weekend which I never did with the 88.

In autocrossing I never left foot brake (left foot was too dumb for threshold braking) and I have always just used the throttle for the things you use both left foot braking and throttle to do, even with totally stock cars. Whenever I left foot braked in autocrossing I slowed down too much . . . maybe because I got on the brakes sooner and lost the "coast time".

Dick

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Dick Rasmussen

FS 50 2018 Mustang GT

Dick,

One place that jumps to mind is the "bitch" on South Course (the first turn off the back straight to join the Patriot Course section). It's a "weird" turn with sort of a double apex and an off camber exit. In Brian Marks' E36 M3 track car, after my first turn in there was a short section of back on the throttle to a mid-point where I could just do this super smooth left foot brake/throttle modulation to get "just the right" amount of rotation right at the apex, and then full throttle drift the car right out to the outside of the off camber exit. It's hard to describe in words, but it was a real treat in that car as it was so responsive and communicated so perfectly with you allowing you to place it and control it so nicely. Brian had to go and sell that car.

In some autox courses, I've found that LFB can really help "thread the needle" on some elements where you are just going for it right the very limits and need to transition the car. The smoothness which LFB allows creates that extra bit of grip by not allowing those throttle to brake to throttle shifts to upset the chassis and contact patch, start oscillations, etc. One of the smoothest LFB driver's I've ever ridden with on an autox course is Jinx Jordan. I spent some of the runs I did with him (Extreme School) just watching his footwork.

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Current stable:
2019 BMW M2 Competition slicktop 6MT
2011 BMW M3 sedan slicktop 6MT
2007 BMW 328i wagon (slushbox for now)
1975 CanAm 125MX2

Since I never learned to left foot brake (kept hitting the brake on upshifts), the subject issue probably would not matter to me. Not being able to heel-toe would really stink. Of course, it's quite difficult on my 2007 already, since you really have to give the throttle a firm push to wake it up. While my '90 5.0 will neither stop nor turn, it does have nice, immediate throttle response.

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Art McDonald
Premier Amateur #518
2008 Dishman Cup
Pivot Cone Snob

Rodney is a waxer (but in a good way)

I really just hope they don't screw up heel toe downshitfing with all this. I don't typically left foot brake, so that part doesn't affect me to much, but I still don't like them restricting things unneccesarily.

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2012 MX-5 Sport SUV