One pedal driving and regen brakes explained: reality, myths, hype, fads and Tesla vs the rest.

Synopsis: Vehicle controls are shaped by history but are still slowly evolving.

Vehicle controls continue to evolve, often because the things in a vehicle that can require control also evolve. This is a look at new EV specific question of controlling regen and the trend of one-pedal-driving as well as some new other new vehicle control systems.

EVs are relatively new, and new thing they need to control is regenerative braking or “regen”. What many don’t realise, is that two different systems for controlling regen have emerged. Some vehicles, including the very significant Tesla vehicles, use a “GO pedal” based regen control system, some use a “STOP pedal” based regen control system, and most brands produce EVs that allow the use of either system.

Using the “GO pedal” based regen system requires adopting an EV specific driving which is highly suited to also adopting “one-pedal-driving”.

Just as only Tesla drivers can need to adapt to using the entertainment screen to see their current speed, it is also so far only Tesla drivers who need to adapt to “GO pedal” based regen control, as almost all other vehicles also provide brake-by-wire that enables “STOP pedal” based regen control, which does not require adapting to a new way of driving. Some who drive a Tesla are choosing to do things differently, so needing to adopt a different driving style in the name of efficiency can be a positive.

But even drivers of vehicles equipped with brake-by-wire where high-regen and one-pedal-driving may even result in reduced efficiency often choose one-pedal-driving.

In fact, although Teslas have always had high GO-pedal regen, Nissan and BMW introduced one-pedal-driving to their vehicles years before Tesla did.

Many people like one-pedal-driving, while some others do not. Some choose one pedal-driving in vehicles where it may be less efficient because they may mistakenly believe that what applies to Tesla vehicles must apply to all EVs, some want to believe it is more efficient, and others choose one-pedal-driving despite not believing it is more efficient.

We have entered an era where people can configure controls of a vehicle to suit themselves, and not everyone makes the same choices.

Which choice is the most enjoyable is personal and this webpaper can’t substitute for people making their own decision there, but it may help break through the myths and misunderstandings about efficiency implications and how systems work, for regen braking, one-pedal-driving, and other emerging new vehicle control options.

Vehicle controls and the Tesla difference.

Control by wire: the ultimate goal?

Vehicle control are all moving to ‘by wire’ means instead of a cable operated by the control physically operating what is being controlled, an electrical signal is sent by electrical ‘wire’ to a control unit which manipulates the equipment being controlled. While control ‘by wire’ means the control no longer need reflect the things needs to be physically controlled, keeping cars compatible means when ‘by wire’ is first introduced operation mimics how things were previously and change is gradual, so history often dictates why things are the way they are.

The end goal of ‘by wire’ controls would be to achieve the simplest and most intuitive controls possible that enable the driver to communicate what they want the vehicle to do. All controls began as ways to mechanically operate components used to achieve what the driver wanted the vehicle to do.

On path to that end goal is “self-driving” where the driver indicates a destination, but there are times such as when off-road when it may be more intuitive to use basic controls to indicate where to go rather than try to specify an exact destination. The basic controls from a logic perspective are:

• Steering: Currently almost always via a “steering wheel”.
• Stop pedal: Or currently the “brake pedal” as directly activating a brake mechanism is currently the normal way to stop.
• Go pedal: Also known as an “accelerator” even though it must be pressed to maintain speed, or a “throttle” or “gas pedal” in reference to mechanisms to control the amount of “GO”.

While many other things, such as ride height and traction modes, may be controlled by a driver these three are the things that all vehicles will likely always need some way of controlling.

ICE Vehicle controls: the starting point.

As the control of todays’ EVs are evolutions of the controls of Internal Combustion Engine Vehicles, that is the starting point for vehicle controls.

Early automobiles were steered by a tiller, but the steering wheel soon took over, and although some vehicles are experimenting with yokes, there is no change brought about by EVs and while steering controls my change, it is not really EVs bringing that change.

Controls for gears have been changed a lot over the years, but as ICE vehicles had already introduced “shift by wire” and clutch pedal are already rare the “gear selector” control of EVs already is similar to use to that of an ICE vehicle even though what is actually happening is very different.

The main remaining controls are the two remaining pedals, which have the functions of “STOP” and “GO”, and these are particularly interesting as because these are what is most different with an ICEV and an EV.

In an ICEV, the “STOP” pedal controls only the friction brakes. This control for brakes began as a lever, and the lever did need to be rather long in order to provide leverage needed by the operator. However, by 1918 when hydraulic brakes first emerged, the control had already become a pedal enabling leg strength to be used, and despite changes to the details and hydraulic assistance being added, and later brake by wire systems, the brake pedal remains a control that can physically control a friction brake system. Even with brake-by-wire, in the event of failure the system becomes a mechanical control of hydraulic pressure.

Next is the “GO” control.

I use the label “GO-pedal” instead of any of the traditional labels of “throttle”, “gas pedal” or “accelerator”, because there is no throttle or “gas” in an EV and the pedal does need to pressed even to maintain a constant speed without acceleration.

In early vehicles such as the Model T ford was a steering column mounted hand control. The pedal control appeared in vehicles like the 1910 Peerless Model 27 and the Cadilac Model 30 which also introduced the electric starter motor, although Wikipedia states Wilson-Pitcher in introduced a foot override for the hand throttle1900 that claim may not be quite right given the company was not formed until 1901, so while one sample car may have been built at that time, it is not clear what was actually introduced in production.

Vehicles with a hand throttle continued for a long time, still being present in off-road vehicles like the Mitsubishi Pajero in 1981 with the hand throttle functioning as form of cruise control.

Although now more commonly known as the “gas peal” or “accelerator”, it was originally called the throttle or “throttle control”, because it controlled a flap that closed off the pipe of fuel-air mix (video here) to be delivered to the engine. Accelerator ‘flat to the floor’ being the throttle ‘fully open’ to allow maximum fuel air mix into the engine. How far the pedal is pressed mechanically controlled the flap allow fuel air mix into the engine.

“GO by wire” required with an EV, and already in use in many modern ICEVs.

The “GO pedal” of a modern ICE vehicle with computer controlled electronic fuel injection is no longer mechanical a ‘throttle’ control as now a computer controls the fuel air mix injected into the engine.

On an EV, a computer controls motor speed, which means that the “GO pedal” on an EV is also a a “by wire” control to computer and the same type of control as an on a modern ICE vehicle.

Where things get more complex, is that historically the “GO pedal” by controlling fuel to the engine, inherently controlled engine braking, as engine braking is an inherent property of an internal combustion engine that happens as a result of reducing fuel supply.

This has meant that traditionally the “GO -pedal” has to some extent been a “STOP-AND-GO-pedal”.

Electric motors do not have any inherent “engine braking” and the closest EV equivalent to internal combustion engine braking, is regenerative braking aka regen, but as regen is not an inherent characteristic of an electric motor and can produce far stronger and more effective braking than engine braking of an internal combustion engine, the question arises as to whether regen should be controlled by the “GO pedal” or more logically by the “STOP pedal”.

Not everyone fully agrees on the answer, but all EV so far do at least offer settings with some regen control from the “GO-pedal” and all major brands other than Tesla also provide regen control via the “STOP-pedal”.

“Stop by wire” aka “Brake-by-wire”: For almost all EVs, but so far, excluding Tesla.

Note: brake-by-wire is also often labelled “blended braking”, but I have avoided this label as Tesla also uses “blended braking” to describe their use of a blend of regenerative and friction braking with the “GO-pedal”, as opposed to “brake-by-wire” with the stop pedal, which is quite different.

I use the label “STOP-pedal” in place of the traditional label “brake-pedal” because on most EVs the pedal no longer directly controls the brakes, but instead sends a signal to the computer that the driver wants some “stopping force” applied and how that is achieved is determined by the computer.

Not all EVs, mainly because Tesla, with a dedication to minimalism and firm belief that the self-driving future is practically already here, eschews using brake-by-wire.

I am unsure exactly when brake-by-wire was first introduced. From this very sound article from Road &Track it was already in use with the first modern EV, the GM EV1:

GM’s infamous EV1 used regenerative braking to improve range, which was controlled by what we now refer to as a “blended” brake pedal. When the driver stepped on the brake pedal in an EV1, the car blended both friction braking and motor regeneration with an extremely complex brake-by-wire system. A press release from back in the day noted that at low speeds, regeneration could handle 95 percent of the car’s deceleration needs.

Road &Track: One-Pedal Driving Isn’t Necessarily the Most Efficient Way of Driving an EV

Which means “brake-by-wire” was in production from 1996 with the GM EV1 if not earlier, for the purpose of allowing the “STOP pedal” to control regenerative braking.

In principle, this means both “STOP pedal” and “GO pedal” become simply inputs to a computer, which means either pedal can be used to do control the motors, regenerative braking, friction brakes, or even steering depending on software. In practice, the big difference between these two pedals is that the “STOP pedal” is designed to directly mechanically control the friction brakes inthe event of a system failure.

The added complexity is the requirement for creating a “by wire” control for braking requires a system that switches automatically to a mechanical control if the computer fails. It is the provision of this “fail safe” that makes “brake-by-wire” more complex than conventional brake pedals, and makes the STOP pedal still physically different in how it operates compared to the GO pedal.

As already mentioned, a hydraulic system to assist with applying force to the brakes was introduced as early 1918 as the system and the force required to push the brake otherwise is too great.

However, the hydraulic system is still not “by wire” as pressing the pedal still directly sends hydraulic pressure to apply force an activate the brakes, so even if the power assistance fails, a person can push as hard as they can, and the car will still stop. If the system fails the assistance is lost, but not the brakes.

For ‘brake by wire’, there needs to be a system that allows the physical pedal to still operate the frictions brakes if all else fails. The problem is, with an EV, mostly the friction brakes are not wanted even when the brake pedal is pressed. The solution is that the hydraulics have valve, kept open by the computer, that automatically closes unless instructed by the computer to stay open. When the value is closed, the brakes are in manual mode as with an ICEV, but normally, the computer handles all braking, and only uses friction brakes when necessary.

The Tesla difference: brake-by-wire vs minimalism & self-driving.

While other EV brands argue that brake-by-wire is necessary for optimal driving efficiency and allowing EVs to be driven efficiently without adopting new driving styles, so far, Tesla vehicles since the Modes S do not include brake-by-wire.

The same applies to providing a display in front of the driver for speed and other information, which again almost every manufacturer other than Tesla provides.

How important are the driver pedals? Already, significant distances are driven using adaptive cruise control systems without any use of the brake pedal. As these systems are computer controlled, they are already able prioritise regenerative braking and deliver optimal efficiency. Tesla already offers “full-self-driving” and is clearly dedicated to a future where almost all driving with need neither a driver display nor driver pedals for stop or go.

So far, just as Tesla drivers seem happy to accept adapting to having no driver display, and many prefer the adjustment to driving style required to drive an EV efficiently without the aid brake-by-wire. and enjoy one-pedal-driving.

Tesla loves minimalism.

That applies to not only cabin ambiance, but also technical equipment, and it is not always even noticeable.

Step into a Tesla model 3, and you can see there is no display in front of the driver. It is obvious.

But not all the things Tesla omits are obvious. If you drive a Tesla, it is not obvious that the driving is different because other EVs have brake-by-wire.

Tesla is also removing RADAR and ultrasonic parking sensors from its cars, but as there are already also cameras, with the rights software it is expected drivers will not experience any difference. What Tesla does is different, and even if it can make driving a Tesla different, it does not make Tesla vehicles necessarily better or worse.

To quote Elon Musk:

Over and over, the tendency is to complicate things. And I have another thing which is, the best part is no part. The best process is no process. It weighs nothing, costs nothing, can’t go wrong. So, as obvious as that sounds, the best part is no part.

Elon Must quotes.

Tesla likes to leave out what it can, and while sometimes the driver must adjust, many drivers see it as preferable in order to experience minimalism.

So far, I am not aware of any other EV without brake by wire. From the launch the Model S, at least until the current date of April 2023, all Tesla vehicles have not been equipped with brake-by-wire. This follows the “no part” philosophy, avoids having one more thing that could fail, some believe delivers a better brake pedal feel.

Regen: It need not make driving an EV different, unless you want it to be.

Overview: The big “you need high regen for efficiency” myth and Tesla difference.

In any EV equipped with brake-by-wire, the full regen potential is available via the brake pedal is pressed, which means whenever the vehicle can use regen and recover electricity. It will. There is no more need to adopt a new driving style to drive efficiently in most EVs than there with a Toyota Prius.

Both “GO-pedal” and “STOP-pedal” of an EV can be used exactly as with an ICE vehicle, and unless the vehicle is a Tesla, the result will be at least as efficient as any other configuration or driving style.

There is a myth that a very high-regen setting, or even one-pedal-driving, is necessary to drive an EV efficiently, but if the EV is not a Tesla, then as explained in this article from Road & Track: One-Pedal Driving Isn’t Necessarily the Most Efficient Way of Driving an EV.

In the USA and many other markets, Tesla has been the dominant EV brand to such an extent than some people thing of all EVs as Tesla vehicles, and there can be an assumption all EVs are like Teslas. The truth is that Teslas are EVs with quirks and differences from other EVs, and while the Tesla way has a lot of very ardent fans, the Tesla way is not the only way.

Regen level settings: A selectable level of regen, or only selectable “GO pedal regen”?

Almost all EVs offer some form of “regen level” adjustment. Even Tesla, who initially offered a “low” regen setting, removed it in a late 2020 software update, but then it was reinstated in an April/May 2023 update.

These “regen level adjustments” are about driver preferences, not some magic that needs to be learnt to drive an EV efficiently. These settings are fine tweaks that as Jack from Fully Charged says, are to some extent for “massive EV Nerds“.

Yes, Tesla vehicles are different, and the lack of brake-by-wire means that, in in a Tesla, changing the regen setting to “low” setting is reducing the amount of regenerative braking available with the impact discussed below, but driving a Tesla on “normal”(full) regen is discussed here and is similar to other vehicles.

That is all for the different, Tesla style regen settings, and the rest of this section applies to other EVs which do have brake-by-wire.

GO-pedal-regen: With brake-by-wire vehicles, “regen” settings are only the “GO-pedal-regen” settings, and do not change the total amount of regen in use.

What is often misunderstood, is that the full regen capability of the vehicle will always be still be available via the “STOP-pedal”. In any vehicle with brake-by-wire, the total regen available is unchanged by regen settings, and all that changes is how the vehicle behaves in response to driver input via the “GO pedal”. Some brands like to try to even avoid the name “regen” with the setting in order to avoid confusion.

The GO-pedal regen is important because it is the regen the driver notices, and “STOP-pedal” regen if configured well feels no different to conventional friction brakes. The difference is only noticeable via a readout of energy recovery.

Many brands even provide dedicated controls to dynamically change the response of “GO-pedal” regen level”, through controls such as steering wheel mounted paddles. The settings in some vehicles can become complex, but in the end the settings are just tweaking response from the pedals to match driver preferences, and all brands keep simple settings for maximum efficiency, because that results in best result on statutory tests that will determine the official range and efficiency.

The bottom line is that default settings will normally be as efficient as any other setting and offer and convenient driving experience enables a driver to drive with optimum efficiency.

Driving with highest possible “GO-pedal” regen: many drivers’ favourite.

The highest setting of “regen” can allow almost one-pedal driving. Using the highest possible regen, with or without one pedal driving, is many drivers’ favourite way of driving an EV either because:

1. They are driving a Tesla and low-regen can be less efficient.
2. Even though driving a brake-by-wire vehicle, the driver mistakenly believes high-regen is more efficient.
3. Regardless of what mode of driving is most efficient, high “GO-pedal” regen is regen you can feel, which is more engaging and provides a new and different experience.

Whatever the reason, many are disappointed with vehicles from brands such as Porsche and BYD that provide no option for their full regen via the “GO-pedal” and only provide the highest regen through the brake-by-wire of the “STOP-pedal”. Some drivers even mistakenly believing such vehicles have “weak regen”, when the reality is all EVs have strong regen, even if on some EVs it requires using the brake pedal. Go-pedal regen is the ren a driver can feel.

Some EVs only offer their highest regen though a setting for “one-pedal-driving”, but the clearest system is one such in Tesla vehicles, where the regen setting and “stopping mode”, which control the use of friction brakes to supplement regen braking at very low speeds, is a separate control. Contrary to popular myth, regenerative braking is ineffective for bringing vehicles to a complete stop. A high “GO-pedal” regen driving mode that still rolls at very low speed allows drivers to train muscle memory for using the STOP-pedal as would be used in an emergency, which could be particularly desirable for new drivers.

The only thing required to move from highest possible “GO-pedal” regen and one pedal driving, is the addition of a system to stop the vehicle at very low speeds. See the section on “one-deal-driving” for full details.

Tesla low-regen setting and efficiency.

The lack of brake-by-wire means the regen from “lifting off” is the only regen, and thus full regen is only available on the highest regen setting.

Using the Tesla “low” regen setting that was initially available but removed in a late 2020 software update but now reinstated in an April/May 2023 update reduces the amount of regen available to the driver.

The reasons for having a lower “Go pedal” regen setting in a vehicle without brake-by-wire are:

• To provide a more familiar experience for drivers unfamiliar with driving with high regen braking.
• Providing a mode with reduced risk of excess use of regen braking, for use on freeways or other times when little braking may be required.

Without brake-by-wire, the low regen via the GO-pedal setting can result in reduced efficiency, and increased reliance on the friction brakes which will increase wear. The low regen setting is best used when vehicles will be driven by drivers unfamiliar with high regen, with Tesla owners best served by becoming familiar with “normal” (full) regen as soon as practical.

STOP-pedal based regen control: An efficient solution for any vehicle with “brake-by-wire”.

An a very efficient alternative to driving with a high “GO pedal” regen setting for drivers of vehicles that are equipped with brake-by-wire is to rely on the computer control regenerative braking when pressing the “STOP-pedal” to result in maximum efficiency.

The regen control many reviewers and drivers mistake for “almost no regen”.

Having a much lower regen level for the “GO-pedal” means that when “lifting-off” there is very little braking effect, leaving many drivers feeling very little regenerative braking is in use.

Porsche raised eyebrows when its first EV, the Taycan, debuted without offering a one-pedal driving mode of any sort. It seemed Porsche was leaving an obvious efficiency on the table, though really, it just chose to regenerate energy primarily with the brake pedal. Up to 0.3gs of deceleration—which covers the vast majority of braking events in everyday driving–is handled by motor regeneration, after which point, the friction brakes are added into the mix. Porsche proudly touts that it can put up to 265kW of energy back into the battery pack, which is more than any other automaker. Additionally, the Taycan will even continue to regen when ABS is activated.

Road and Track: One-Pedal Driving Isn’t Necessarily the Most Efficient Way of Driving an EV

After years of EV market dominance by Tesla, and ICE vehicles without brake by wire, many people assume that pressing the brake pedal simply activates the friction brakes. For those not being aware of “brake-by-wire” assume Porsche must be crazy to omit high “Go pedal” regen and one-pedal-driving. However, the reality is Porsche offers even higher regen than any Tesla does, just the Porsche only offers that high regen via the brake pedal.

This mindset shaped by experience with Teslas created the false belief that high GO pedal regen is necessary for EV efficiency.

Although technically this approach can offer even greater efficiency that used by Tesla, in practice any gains are difficult to detect, and the main benefit is that drivers do not have to learn a new way of driving. Which would be a big plus if not for the reality that many drivers want to adopt a new way of driving when moving to an EV!

Of the major brands, it is not just Porsche. BYD, the brand producing even more electric vehicles than Tesla, and who even supply battery technology to Tesla, also eschews using the “GO pedal” as the main control of high levels of regen and discourages one-pedal-driving.

With this approach, driving an EV feels like driving an ICEV vehicle. Which, even if technically more efficient, for many drivers is a problem.

Because the main management of regenerative braking results from the driver pressing the “STOP-pedal”, GO-pedal regen can be configured to create a familiar driving experience. Because brake-by-wire means that a computer is now controlling what happens when the STOP-pedal is pressed, the outcome still feels just the same is the outcome from pressing a conventional brake pedal.

Both GO and STOP pedals produces responses that feel like what happens with driving an ICE vehicle, even though underneath fully optimised regen is being used whenever braking is required.

The efficiency results from the computer using maximum regen braking before applying the friction brakes, and the efficiency is computer controlled rather than manually controlled.

The biggest negative is that it feels just like driving an ICE vehicle instead of providing the driver a new and different EV driving experience.

Drivers don’t get to feel that regen is at work when braking is activated by the STOP-pedal the way they do when it is activated by the GO-pedal, but most EVs provide a display indicating the power being either used or regenerated and reading that display can be the only real indication of the role of regen in proving any braking force.

One Pedal Driving: Popular way to drive an EV, or a fad?

What is one pedal driving?

In theory, one-pedal-driving means only one of the two pedal controls in an EV are required during normal driving: the GO pedal.

EVs still all have 2 pedals, just as with ICE vehicles with an automatic transmission. There is never a third “clutch” pedal control in any current EV, but the “GO pedal” and “stop pedal” are both still present with the left pedal as the “STOP pedal” and the right pedal “GO pedal” as usual.

The left pedal, the “STOP pedal”, is in fact very much still required, it is just in theory rarely required, so the label “one-pedal-driving” is something that can be done for periods of time, and not a always being able to fully control the vehicle by only the one pedal.

How one pedal driving works: The steps required.

The is a common misconception that one-pedal-driving avoids the use friction braking. This is wrong.

One pedal braking works by providing both regen braking and friction braking and can activate all of the following steps simply as a result of lifting-off the “GO-pedal”:

1. Regen braking: Up to the very maximum use of regen braking practical for the vehicle.
2. Low speed friction braking: Application of friction brakes to take over from regen braking at very low speeds when regen braking becomes ineffective and only minimum friction braking is require in order to bring a vehicle to a halt and then keep it stationary.
3. Supplemental friction braking(optional): An optional but desirable application of the friction brakes to supplement regen braking to provide consistent response in circumstances when the battery is unable to support normal usual levels of regen braking.

Despite the two cases where friction braking is required, unless the brake pedal is used, the regen braking supplies almost all the braking force and the contribution of the friction brakes has a negligible impact on efficiency and little contribution to wear on the friction brakes. However, understanding the role of the friction brakes is key to understanding the limitations of regen braking.

Step 1, regen braking, is obvious. Steps 2 and 3 are less obvious.

Tesla introduced “step 2: low speed friction braking” in 2019 which is what made one-pedal0-driving made one pedal driving practical in a Tesla:

Stopping Mode enables the 100% one-pedal driving many people have heard about but Tesla has never offered. Tesla cars have almost allowed one-pedal driving, but only slowed to about 3 miles per hour, so you would need to tap on the brakes to avoid rolling into either the intersection or the car ahead of you.

Tesla One-Pedal Driving Update — In A Word, Perfecter

Tesla introduced step 3, the automatic use of friction braking to supplement regen braking, perhaps as recently as May 2022 although I had thought Tesla had earlier implementations.

Outside of China, since 2017 the most popular EVs have usually all supported one-pedal-driving since 2017.

The Nissan Leaf introduced one-pedal-driving in 2017, and at that time was the most popular fully electric car in the world and around the time Tesla took over as the biggest selling EVs Tesla also added featured one-pedal-driving.

This means most EV drivers have had access to one-pedal-driving, and many now view one-pedal-driving as a defining feature of a vehicle being a true EV. The misunderstanding is that many people mistakenly think one-pedal-driving is essential for efficient driving of an EV, when there are other alternatives that are, equally efficient, or potentially more efficient.

Whilst some articles do report one pedal driving is NOT the most efficient approach, it is only in vehicles, that unlike Tesla vehicles, are equipped with brake-by-wire that these potentially more efficient approaches as possible. This quite thorough article examines some of the alternatives offered by other brands.

How to configure and optimise one-pedal-driving.

How to configure the EV for one pedal driving varies from EV to EV. For most EVs, it is “regen setting” choice, but for a Tesla, the main requirement is to set the stopping mode to “hold”, and the preferably the “regenerative braking” set to “standard” and not “low” in order to allow maximum possible “GO pedal” regen control.

With one-pedal-driving enabled, an EV will decelerate towards a stop whenever driver stops pressing the “GO pedal”.

In one pedal driving, press the Go pedal harder to go faster and ease off to go slower. Completely easing off the “GO pedal” will make the vehicle stop quickly enough for most situations, which means that the STOP pedal will be rarely required.

The two main goals for efficiently using one-pedal-driving, in order are:

1. Try to avoid needing the unnecessary of friction brakes.
2. Avoiding the unnecessary use of even the regen brakes.

Number 1 is all about avoiding creating situations when more braking force is required than what is available from backing off on the “Go pedal” alone. This requires anticipating traffic and starting braking early.

Number 2 is avoiding the trap of thinking that regen braking is “free” in that it loses no energy at all or even means gaining energy. All energy gained by regen will never be as much as required to get the speed (or altitude) back again.

Given the STOP-pedal is still required for an emergency stop, it may be useful to have new drivers spend considerable time without using one-pedal-driving until the reflex for an emergency stop is well established.

Why don’t all EVs feature “One Pedal Driving”?

It becomes a interesting question when you consider there is zero real cost, and the answer is: because they don’t want to!

Even Tesla was “late to the party” with one-pedal-driving, adding the feature as a no cost software update in 2019.

All that is required to provide “one pedal driving” is for the “Go-pedal” to be “go-by-wire”, and as all EVs have “GO-by-wire” every EV can offer one-pedal-driving by simply providing right software.

All modern EVs have “GO” being “by wire” as the computer controls for the motor. This means that instead of the “go pedal” mechanically operating mechanical systems to control speed, as was the case with the throttle on the original ICE vehicles, instead with EVs the “GO pedal” provides a signal to the vehicle computer systems.

With this “GO” being “by wire”, the vehicle computer system can determine how to interpret the implications for how far the pedal is pressed. Since the computer has full control over motor power, motor based regenerative braking and, at least on any vehicle with an adaptive cruise control with stop-start, the ability to apply friction braking.

So, any EV can have “One pedal driving”, and all that is required is software.

Reasons a brand does not provide one pedal driving could include:

• Concerns one-pedal-driving can be less efficient than alternatives for brake-by-wire vehicles.
• Concerns over safety as drivers become less practiced as use of the brake pedal.

Any EV that does not have one pedal driving could get one pedal driving through a software update, but it could take a change in philosophy.

Why, or why not, use one-pedal driving?

The logic behind each of the identified for choosing maximum “GO-pedal” regen, suggests in every case it makes sense to add that second step 2 of low-speed friction braking and use one-pedal-driving. Although it is generally a myth that adding this step is more efficient, there is also no reason it would be less efficient. An even more satisfying experience of what feels like engine braking beyond that offered by an ICE vehicle, with zero loss of efficiency.

The overall effect is a new and different driving experience, and most people enjoy new experiences. Many people feel that moving to and EV is far more satisfying if there is also a new driving experience.

Downsides? It can take a little practice, it may not be the most efficient way of driving, and it is important to maintain the reflex to still use the brake pedal in an emergency.

On the subject of practice:

If you’ve ever driven a Tesla, the first time probably went something like this: Everything’s going fine until you need to gently slow down. You lift off the accelerator pedal, and wham! You nearly come to a complete stop. If you have passengers, they probably hate you.

Road and Track: One-Pedal Driving Isn’t Necessarily the Most Efficient Way of Driving an EV

This learning curve already applies to use of high-regen, and adding one pedal-driving does not result in there being more to learn, with some even feeling one-pedal-driving make regen more natural, as the strong braking effect continues rather than fading away as the available energy for regenerative braking to harvest falls away.

The biggest potential downside would be if needing to use the brake pedal became too rare, causing the reflex to reach for the brake in an emergency to become “rusty”. There have been some EV crashes where this may have been the cause, but people to failing to brake in an emergency also happens in vehicles without one-pedal-driving.

Is one pedal driving a FAD?

For many, one-pedal-driving has been part of the “EV experience”, but once EVs are common, will it still make sense?

It would make even more sense if we could genuinely eliminate the need to press the STOP-pedal, but would we really want to remove any way of overriding “GO” in an autonomous vehicle?

Formula 1 race cars have not adopted one-pedal-driving, which also highlights the limits of the system. One-pedal-driving, by providing no access to full braking force, is inherently limited. It may even be that the use is limited to the vey situations where the goal is “self-driving” as opposed to the racetrack.

Plus, it is not necessarily efficient.

But if it is a fad, then it is clear there is an appetite for something new. Perhaps one-pedal-driving via the “STOP-pedal” could be made even more workable, particularly if combined with a degree of self-driving, where the driver can still overrule the system by slowing? It seems to make little sense for the driver to be intervening to go faster, just as it seems illogical to have what is a separate control for “STOP…NOW!”.

Fun vs Efficiency: is one-pedal-driving or high regen more efficient or more fun?

What are the options?

It very much depends on whether you are happy with an EV that drives like an ICE vehicle. A Tesla is very much designed for people who want something different, while owners of an EV Porsche may want an EV that still drives like a Porsche. If the vehicle will be predominantly vehicle will be using adaptive cruise control or autonomous driving, then settings for how the pedals behave should have negligible impact on efficiency, so the priority may be what a question of the driver finds more fun when they do take over.

There are a few scenarios that depend on vehicle:

• For a Tesla the choice will normally one-pedal-driving but perhaps a choice of low-regen for maximum range on a long bland freeway, although in those circumstances the vehicle maybe self-driving anyway.
• For a Porsche or BYD^* and some others its low regen for efficiency or performance but while there somewhat higher GO-pedal-regen for a possible change, there is no option of no one-pedal-driving and regen is mainly via the STOP-pedal.
• For almost all other EVs, it is choice of being like a Tesla for fun and something different or provided there is brake-by-wire unlike a Tesla, then using low regen like a Porsche or BYD for maximum efficiency.

The beg caveat is that many times when driving for efficiency, autonomous driving may be active, so the settings may more be about whatever the driver prefers, of for when efficiency is not important.

*While all Porsches are performance vehicles and BYD vehicles can include the Seal or U9, but although not all BYD vehicles are known for performance there is still no one-pedal-driving.

Making a choice: For most driving, do what you enjoy, that will work best!

In a Tesla, or any other vehicle without brake-by-wire, a higher regen setting does technically enable more efficient driving.

In any vehicle with brake-by-wire, the same efficiency is technically possible with any available setting, and all regen settings do is change which pedal is activating the regen.

In practice, even though the same efficiency is possible with different settings, achieving the technically possible optimum efficiency does get easier with a lower regen setting. One-pedal-driving is in reality more about driving fun than efficiency, and not matter how many myths people choose to believe, the two have rarely gone hand .

But also in practice, efficiency in an EV matters most because range matters most when on a long trip on a quite bland highway, which is normally when there is far less braking, which will usually mean there is least to gain from regenerative braking and most to lose controls being overly sensitive resulting in applying unneeded braking.

Even when driving in urban conditions, where EVs are all so much more efficient than ICEVs that small differences in efficiency often matter, many drivers are often using adaptive cruise control or other driver aids, which result in the human driver rarely pressing the “GO-pedal” anyway.

A practical example.

With a Tesla, if you cannot get better result with “standard” regen, then you may need more practice. I conducted some tests with a BYD vehicle with brake-by-wire, and personally found I consistently achieved slightly better efficiency using a the lowest “regen” setting. Working harder to avoid “lifting-off” more than absolutely necessary and thus avoid activating regenerative braking more than necessary, and it was sometimes more work, but did marginally improve results which confirms that changing regen settings can make efficient driving less work.

But a big surprise when I found a learner-driver I had been instructing achieved better efficiency than I did over a similar course. I have been trained in rally, racing and advanced driving, and yet a learner who still had more to learn could be more efficient? Really? Further analysis revealed they were driving slightly slower on average, and this was the reason. In reality, if you want a little more efficiency, driving slower is a simpler and more effective manner than almost anything else, but it is less fun.

For maximum highway range: use the lowest “regen” if possible.

There can be times when maximum range is needed to reach the next possible charging point, and on the few occasions this does occur, it will be when travelling between towns or cities on the highway.

With a Tesla or a vehicle or without brake-by-wire, “if possible” means “if driving on low-regen does not result in needing use of the brake pedal under normal conditions”. If low regen is possible, it will make fine control of the amount of regen simpler. However, if the vehicles will be using adaptive cruise or autonomous driving the entire time, the setting may make no difference.

With any EV with brake-by-wire, which so far means any EV other than a Tesla, low-regen should, and normally will, be the safest way to ensure maximum range. Also consider the more technical answer.

The more technical answer.

There is evidence that Porsche is correct, and that in vehicles equipped with brake-by-wire, a very low “regen” setting will be most efficient, even though for those accustomed to Tesla vehicles, this can feel like “there is no regen!”

Tesla makes a high regen standard for a reason, but then added the option restored the low regen option for a reason.

Follow brand guidelines. If brand has a recommend setting, there is a reason. Also, it is worth considering if the guideline for when to use a setting apply for the situation in question. Many guidelines are designed around the testing procedures for consumption the car will need to pass such as EPA, WLTP, etc. as having the best figures on these tests can really help sales.

Brands work very hard at achieving the best efficiency for the vehicles during the test cycles.

Unintended acceleration and one pedal driving.

Wikipedia currently 6 factors as potentially responsible for sudden unintended acceleration:

1. Pedal misapplication^[3][1][9]
2. Unresponsive (entrapped) pedals^[10]
3. Electronic throttle control or cruise control failure (see drive by wire)^[11]
4. Stuck throttle (unrelated to pedal position)^[12][13]
5. Shorting of tin whiskers^[14][15]
6. Diesel engine runaway – excessive pressure in the crankcase can force mist of engine oil into the intake manifold, which can be burned in the same fashion as diesel fuel.

The only link being suggested here between one pedal driving and unintended acceleration is “Pedal misapplication”. This is the type of unintended acceleration that can be considered as the fault of the driver, because it is the driver pressing the accelerator instead of the brake when they wish to stop the car. Many learner drivers make this mistake at least once while learning, but over time pressing the brake pedal to stop becomes “muscle memory” that no longer requires conscious thought. But could use of one-pedal-driving result in new drivers have a weaker muscle memory to push the brake pedal, potentially resulting in increased unintended acceleration as a result of pedal misapplication?

The answer so far is “maybe”? Being a theorist, not an experimentalist, I look for data collected by others and will link data here:

• Whistleblower Drops 100 Gigabytes of Tesla Secrets to German News Site: Report
• Tesla recalls over 1.1 million vehicles in China for issues including regenerative braking strategy
• Fatal accident puts Tesla in spotlight in China

Tackling myths and misunderstandings.

Regen is not only what drivers feel when lifting of the “GO pedal“.

Many “road-tests” of vehicles report vehicles without strong regen as a result of little “regen” being evident when lifting off on the “GO-pedal”. Consider these passages from this 202 review of the Porsche Taycan by an experienced EV journalist Tom Moloughney:

Porsche’s implementation of the regenerative braking system for the Taycan is different than the systems on other electric vehicles available today. It’s both very strong and very weak at the same time, it just depends on how you look at it.

………

To put the Taycan’s 265 kW regenerative braking potential into perspective, the Tesla Model 3 can generate a maximum of 77 kW, less than 1/3 of what the Taycan is capable of pumping back into the battery.

….

Many of these EVs employ a blended braking system which, when depressing the friction brake pedal, increases the amount of regenerative braking while also employ the actual friction brakes.

This is what the Taycan does, except the lift-off regeneration force is milder than on most other EVs. In fact, you can barely feel the vehicle slowing down from recuperating, it basically feels like the car is coasting. However, when the driver presses the friction brake pedal, the Taycan doesn’t actually actuate the friction brakes unless you really need to stop in a very short distance. What is actually happening, is the vehicle is stopping by using engine braking and recuperating as much energy as possible.

Unlike the Taycan, Tesla doesn’t employ a blended braking system.  The regenerative braking works strictly on lift-off and the brake pedal is only used to control the friction brakes. They have a setting for strong lift-off regeneration and one for weak lift-off regeneration. There’s no additional regenerating when depressing the friction brake pedal, as most other EVs offer. 

We Evaluate Porsche Taycan’s Unique Regenerative Braking System

The article is very much about a person accustomed to thinking in terms of “lift-off regeneration” coming to terms with:

So what Porsche did was to implement a blended braking system, where the lift-off regeneration is extremely mild, but the brake pedal regeneration is very strong.

We Evaluate Porsche Taycan’s Unique Regenerative Braking System

Even to an experienced journalist, the concept of a vehicle having high-regen, but that regen not being evident when “lifting-off” was radical. Unlike others with less experience, Tom Moloughney did not fall for the trap of assuming that low “lift-off” (GO-pedal regen) means low regen, and mistakenly assuming that the brake pedal will always activate friction brakes (I believe that reviewer also now understands having now worked with others, but videos are not easy to edit).

This myth that “GO-pedal” is the only regen, perpetuated by the lack of understanding of brake-by-wire , is the biggest myth around regen and one-pedal-driving.

One-pedal-driving can be less efficient than more conventional driving.

There are so many myths around “high-regen” and one-pedal-driving but the most culminated in the belief that one-pedal-driving is some holy grail of efficient EV driving. It isn’t. Road & Track explain in this article: One-Pedal Driving Isn’t Necessarily the Most Efficient Way of Driving an EV.

It is not that one-pedal-driving is inefficient, just that it can be slightly less efficient than more conventional “GO-pedal” response and using the STOP-pedal. One-pedal-driving can still be satisfying, and ther is no reason to avoid its use, but niether is there any reason to feel it is in some way necessary.

Consider the following other myths tacked by:

• Regen braking is not the main reason EVs are efficient.
• EVs are not less efficient on the highway because there is less chance to use regen.
• Regen braking does not bring vehicles to a complete stop.
• No, regen settings do not change available regen.

These myths all contribute to the myth of one-pedal-driving being necessary rather than just fun.

Vehicles identified as having “low regen”, often have very powerful regen.

See the previous myth. This is mistaking the amount of regen a vehicle has based on what is felt from the “lifting-off” or “GO-pedal-regen” is also extremely common.

No, regen settings do not change available regen.

OK, Tesla is at least partially an exception due to the lack of brake-by-wire, but even on a Tesla, full regen is always available when using “auto-pilot” or any other automated driving system.

With other EVs, “regen-settings” just change how the “GO-pedal” is configured, and full regen is available via the STOP-pedal.

Regen braking is not the main reason EVs are efficient.

In hybrid vehicles, regen braking plays a more significant role, but even in hybrids just the use of an electric motor to aid acceleration reduced fuel consumption and allows use of a smaller less powerful gasoline engine, further improving fuel consumption, and regenerative braking is only one part of the improved efficiency.

With an EV, the main gain in efficiency is elimination combustion, which converts the energy in fuel into heat, and most of the heat is lost through the radiator and engine cooling system and the exhaust with only around 25% of the heat typically able to be converted into moving the vehicle.

Regen is still a form of braking and is not more efficient driving without using the brakes at all.

All use of any form of braking is results in wasted energy. Slowing down reduces kinetic energy. Regen can save around and then later return as much as 70% of the kinetic energy, while friction braking saves 0%, but still around 30% of the energy lost.

EVs are not less efficient on the highway because there is less chance to use regen.

EVs are actually more efficient on the highway than they are in urban driving, and EVs are less efficient when they need to use regen than when no brakes are required. The reason EVs use consume more energy on the highway, is because going faster requires more energy. Air resistance increases with the square of speed, so for 2x the speed, the air resistance increases by 4x!

Familiarity with ICE vehicles creates a distorted perspective.

How can ICE vehicles have low consumption at higher speeds?

Internal combustion engines mask the impact of speed on the need for energy because the provide increased efficiency as they are required to work harder at greater speed. Unlike an electric drive train, where efficiency is high at all times, the efficiency of an internal combustion engine can vary from around 5% at very low loads, to 30% and in some cases higher at higher loads.

So, with an ICEV the effect of driving faster is in part compensated for by the energy improving in efficiency. The result is that factors that have a big impact on EV efficiency, matter less with an ICEV. The problem for ICE vehicles is that operating at low loads is problematic, which means stepping up to a more powerful internal combustion engine, can make a vehicle less efficient when driven at normal speeds.

Regen braking nis not what makes EVs efficient. EVs, like other vehicles, are most efficient when it is possible to avoid all braking.

Regen braking does not bring vehicles to a complete stop.

In one pedal driving, the last bit comes from using the friction brakes, which does not harm efficiency.

Look at what Tesla changed in order to introduce one-pedal-driving: they introduced stopping mode in addition to high-regen. Previously, or without stopping mode, regen becomes ineffective at around 3 mph. Do people really think Tesla turn-off regen braking when the vehicle slows unless “stopping-mode” is set to hold?

Consider how regen-braking works. The key is the word regenerative. The braking power comes from absorbing the electrical energy generated by using the motor as a generator, and the efficiency come from the fact that there is electrical power being generated. Regen braking only functions when the vehicle has enough kinetic energy that turning the motor generates electricity.

The faster the vehicle is moving, the better regen works, but there is a lower limit regen braking being of any use. The good news is that at the speeds when regen stops working, friction braking works extremely well. These are the types of speeds when friction brakes work so well that new drivers end up stopping being stopped before they expect, as less friction brake force is needed when nearly stopped.

At these low speeds, there too little energy to harvest, but also too little energy to worry about being lost, or to cause wear on the friction brakes. There is no real cost to the fact that friction brakes come into play for stopping, but it can still be worth understanding.

Regenerative braking cannot keep the vehicle stationary, as it is not practical to be generating electricity from a stationary vehicle!

An electric motor can be used to hold a vehicle stationary, but doing so consumes electricity and would eventually flatten the battery and is definitely not regen braking, nor a sensible idea. Again, friction brakes are the best solution and use no energy keeping the vehicle stopped.

Regen braking does not spin the electric motors backwards!

I have seen this myth written on several pages and repeated in online videos.

The motor of an EV is connected to the wheels. When the motor spins backwards, it makes the vehicle moves backwards. It is called reverse!

Further using the power of the motor to push against movement would require using energy, while regen braking is generating energy.

As explained in more detail below, the motor, when used as a generator, resists being turned, and the vehicle forcing the moot to be rotated generates electricity.

Background: An In depth look at brakes of varied types.

The principle of braking: Conversation of energy.

There is a principle of physics: Energy is never created or destroyed.

Energy from the battery or fuel tank is converted into kinetic energy: the energy of motion.

The goal of brakes is to reduce speed, which requires converting the energy of motion into a different form of energy. The rule “energy is never created or destroyed” means braking will always be transforming kinetic energy into another form of energy.

Every type of brake needs to have a way to dissipate the energy produced by concerting the kinetic energy into a new form of energy.

Friction brakes.

Friction brakes transform the kinetic energy into heat and must be able to dispose of the heat in order to continue converting kinetic energy into heat.

Disc brakes and drum brakes are both types of friction brakes. Friction brakes convert the kinetic energy into heat energy. The hotter friction brakes become, the less effective they become as their capacity to accept even more heat becomes reduced. To not lose effectiveness, friction brakes need to be able to dissipate heat, which gives rise to ventilated disc brakes.

Internal combustion engine braking.

The engine braking of a combustion engine also converts kinetic energy into heat, by using motion to pump or suck and compress the air in the cylinders. Compressing the air raises the temperature of the air, which is pumped through the engine transferring heat to the cylinder block and out through the exhaust.

Air brakes.

Just for completeness, “air brakes” are not a form of air compression braking, but simply and alternative way of operating friction brakes.

Regenerative braking.

Principle.

Regen brakes transform the kinetic energy into electrical energy, and must be dispose of electrical energy in order to continue converting kinetic energy into electrical energy.

Note that regen braking is just one form of possible braking by than electric motor: it is the efficient braking that recovers energy.

An electric motor can also be used applying power to exert a force against the motion of the motor or exert a for force to resist a stationary motor beginning to spin or rotate, but both of these methods would consume energy from the battery and generate heat, and thus are less efficient even than friction braking, which wastes energy, but does not consume energy!

Regenerative brakes use an electric motor, with the motor configured to operating as a generator, and thus to convert kinetic energy into electrical energy.

How this works, is that moving a magnet past a conducting coil generates a voltage. The means that, since rotating an electric motor rotates a coil past magnets, rotating a permanent magnet electric or induction motor with power to the magnets will generate voltage. Since generating voltage requires energy, this creates resistance to rotation, but once the motor is up to speed, as maintaining the voltage requires no extra energy, the resistance diminishes.

However, if an electrical load such as a circuit with a battery is connected across the coil causing a drop in voltage, spinning the motor will then require whatever force is necessary to restore the voltage. Add the electrical load which consumes some of the voltage, and the motor becomes hard to turn. This is regenerative braking.

Testing the principles.

These principles can all be tested with an appropriate electric scooter or electric bike. I tested with a Unagi scooter that seems to use induction motors, so it needs to be switched on to see the effects and there is no noticeable resistance to pushing the scooter when it is “off”, as would be expect from induction motors, and is consistent with the scooter offering selection between either 1 or 2 motor operation. When “on”, there is force needed to start the scooter rolling, but once at walking speed there is negligible resistance to keeping the scooter rolling. The Unagi scooter has regen braking that cannot fully stop the scooter but can slow the scooter sufficiently for the rider to need to use one foot for stability.

The power of regen braking is determined by the amount of power produced by the electrical “load” of the circuit charging the battery. At very low speeds, there is insufficient voltage to power the circuitry that charges the battery,

The effectiveness of the regenerative braking is reliant on the ability to ‘dissipate’ electrical energy by storing that energy it in the battery. Without keeping the voltage at the motor below the voltage generated by spinning coils in a magnetic field, the braking effect would become minimal far sooner than a friction brake becomes too hot, but as long as the electric power can be transferred to the battery as electrical charge, regenerative brakes can prove an effective and almost wear free brake system that generates electricity. The latest Formula-E race cars, have no other rear brakes!

What really limits regenerative braking?

In a vehicle without brake-by-wire, regen can be limited by the amount available from lifting off the accelerator, but this is mostly a constraint of the past, for todays’ vehicles, the limits are mostly determined by:

• The power of the motor(s).
• Front-wheel-drive vs rear-wheel-drive vs all-wheel-drive.
• The ability of the battery to accept charge.

The power of the motor(s): the more powerful a motor, the more deceleration it can provide, and hopefully this needs no further explaining.

Front-wheel-drive vs rear-wheel-drive vs all-wheel-drive: While the main wheels for handling around curves and for acceleration are the rear wheels, the main wheels for braking are the front wheels. The best possible result for regen braking is from most regen braking power from the front motor and less regen braking power from rear motor. Ultimate regen braking power, as with Formula-E is determined mostly by the regen braking of the front motor, but the gentler the braking, the less critical it becomes whether the braking is from the front or rear, but the best balance will aways be when the front wheels are doing most of the braking.

The result is the friction brakes are needed most in a rear-wheel-drive vehicles, less in front-wheel drive-vehicle, and even less in all-wheel-drive vehicles. Rear wheel drive better for ‘go’, front wheel drive better for ‘stop’.

The ability of the battery to accept charge: Braking is about converting the energy of movement into another form of energy and are limited by the amount of energy they can deal with. Just as friction brakes are limited by the amount of heat they can dissipate; regen brakes are limited by the amount or electric charge they can send to the battery at the current state of charge. A vehicle with a flat charging curve can handle a similar amount of max regen at all levels of charge, while a vehicle with a peaky charge curve will likely vary more in terms of regen braking relative to state of charge. Many vehicles have regen-charging limits higher than the regular charging limits, due to the fact that the duration of regen is much shorter than that of charging.

More new vehicle controls.

Steering by wire and funny yokes.

Several brands see the introduction of new EVs as an opportunity to introduce new controls. Telsa, Lexus and BYD among those looking at steering yokes, that look similar to those in F1. Note that in F1, the steering yoke can only be rotated by slightly less than a half circle in either direction, which allows the drive to keep their hands in place with no need for arms to cross. An F1 car has a huge turning circle and would be useless in a car park. Even on the racing track, it is necessary to spin the rear wheels and force a slide to do a U-turn. Getting a yoke to work in a vehicle that must also be maneuverable in a parking lot is a very different challenge.

This video gives some analysis, but it deserves more, and I do not think Lexus is there yet either.

Camera based “mirrors”.

This is another new topic, with analysis still to be added.

The challenge of replacing mirrors with cameras is that while driver can maneuver their head to “pan” the view available in a mirror, no one had yet provided an equivalent in a camera-based system.

Updates.

• 2023 May 27 th: Added “Unintended acceleration and one pedal driving“.
• 2023 May 12 th: launch as a stand-alone page.
• 2023 January 7 : More on one pedal driving.

Future Updates: Induction and other content to follow….