Nissan LEAF Shifter FAIL

The LEAF's shifter or gear lever — old terminology doesn't quite fit a reversible electric motor that doesn't need multiple gear ranges — is another example in the alarming trend of return-to-center automatic transmission gear selectors. I don't condemn it because I don't understand it or just because I somehow fear change. I condemn it because the LEAF shifter and those like it are a design failure on their own merit.

I concede it doesn't take too much effort to acclimate. I'm suggesting that any change is not only pointless but also potentially confusing and, therefore, dangerous.

Clarity of State FAIL

The primary trouble with these shifters is they fail to provide good feedback a driver can instantly and clearly detect as to which mode is selected. The control looks exactly the same no matter what gear the car is in.

The LEAF indicates its driving mode with lights. There are green LEDs behind the shifter that mostly indicate the mode. (D and B are ambiguously denoted by a single light, though both modes understandably produce forward movement.) Unfortunately these indicators are well out of the driver's normal sight lines and get washed out to invisibility in direct sunlight. Like a lot of conventional automatic transmission cars, there's a much more useful letter indicator in the instrument cluster (which does differentiate D and B), a good solution even though it is somewhat dissociated from the shifter by distance and an inherent lack of feel. And the digital gauges also get plenty washed out in direction sunlight, something that cannot happen with a physical lever that stays where you put it.

In all of the control operations described below, the actual control lever/knob/button returns to its starting position leaving no physical indication whatsoever in what state the car is or what will happen when one presses the accelerator or steps out of the car.

Unambiguous Control Input FAIL

Operation is where the LEAF's shifter gets really weird. Most of the problem with this design is that instead of staying in place after selecting a mode like a vast majority of shifters before it, this knob moves back to its starting position. But there are internal inconsistencies as well.

Reverse
In order to put the car into reverse, one slides the knob left and then forward. I'm not quite sure why a fancy, futuristic, electronic directional control would use the opposite direction of travel to select reverse. It may have a lot to do with the position of reverse relative to neutral and drive in the established PRNDL (Park, Reverse, Neutral, Drive, Low gear) automatic shifter pattern. This fails to mimic that familiar pattern because the lever's starting position is opposite when performing the most common reversing operation, backing out of a parking space.
Neutral
Disconnecting the prime mover or parking pawl from the wheels is accomplished by sliding the knob left and holding it there for a few seconds instead of moving it forward or back. Consider this a long press in touchscreen parlance. It's not a frequent mode selected but it somewhat breaks the paradigm established by drive and reverse which don't require a hold time.
Drive
Complimentary to reverse, slide left and then backward to engage forward movement.
B or Extra Braking Mode
Braking mode is a feature to signal to the regenerative braking system the intent to maximize its use to slow the vehicle and put as much of that energy as possible back into the batteries. Selecting this mode is the identical movement as selecting drive. In fact, this movement toggles between D and B, further confusing the movement/position = operation/state problem. Both modes engage forward travel so I concede this doesn't conflict in the bizarre paradigm implemented by this control. A discrete control that definitely selects B instead of maybe selects B or D would be a lot clearer. Yet still I think it better indicated by sliding a shifter into the traditional L, an equivalent function to the old low gear for descending hills regardless of its enhancement to battery charge.
Park
All of the modes above are achieved by sliding the mouse-like shift knob around a flat plane. (OK, a spherical section.) Park, however, is engaged by pressing down on a button in the top of the shift knob. Every dealer test drive I've ever been on in a LEAF has been prefaced by specific and careful instructions on how to engage park (and I see them eyeing me until I press the button), a sad testament no doubt born from experience to how weirdly non-intuitive this function is to newcomers. (Of course this only engages a pawl. I always recommend setting the parking brake on manuals, automatics and electrics alike.)

As can be seen above, the functionality of all the possible mode/gear selections are identical between the LEAF and a conventional automatic. Not only are the LEAF's controls inconsistent with the familiar automatic transmission lever, they are internally inconsistent and ambiguous.

I would strongly caution against discoverability, a Silicon Valley buzzword commonly associated with low risk graphical computer human interfaces. The consequences of operating a motor vehicle are too high to leave to guessing and idle exploration.

Futurism FAIL

I've heard it all before. I get it. This is a new kind of car that eschews tradition, leaps ahead of Edwardian era chemical combustion power and blazes a trail to a clean, peaceful future free from oil dependence. Great. I'm all for it. (A big thanks to Tesla for showing us that EVs don't have to mean a sterile econobox dystopia.) And why shouldn't a futuristic new car have a futuristic new interface that discards century old anachronisms?

The problem is: It isn't. First and foremost, the LEAF is a car. It is not a special and unique snowflake. It is a step forward in the technological progress of personal transportation just like every other new battery electric, internal combustion engine and hybrid vehicle. Just like the rest, it is a car and it must function like any other car. It is undeserving of a unique user interface for common functionality.

The fact is, most automatic transmissions have been electronically controlled since the '80s and '90s. The same is true for newer single- and dual-clutch automated manual gearboxes and CVTs. There's no reason those transmissions couldn't have been controlled with logic-voltage, momentary switches (they are inside the shifter mechanism) or even a web interface or smartphone app to take it to a silly extreme. The revolution was heralded by the first electronic kick-down switch under the accelerator pedal. The point is, those transmissions were not given new user interfaces because it breaks a well-understood, time-tested paradigm.

As it turns out, not understanding history is a sure way to repeat its mistakes. The old PRNDL (PRND321 or whatever manual mode replaces low on your 10-speed) pattern is really only about 50 years old relative to the LEAF. When fully automatic transmissions were still fairly new in the 1950s, every manufacturer had their own pattern. GM's popular and reliable Hydramatic used a PNDLR pattern that put forward and reverse gears next to each other. Some didn't have a parking gear at all. Chrysler's famous push button automatic had a familiar RNDL arrangement of buttons with park on a lever to the side. Ramblers had push buttons too and high-end Edsels had them in the steering wheel hub where you'd expect the horn button! But at least the buttons stayed pressed when a gear was selected. Beyond various problems with those individual patterns themselves, the real trouble was that they were different. Moving from one car to the next could mean accidental confusion resulting in something from embarrassment to mechanical breakdown to tragedy. This problem consumed the entire second chapter of Ralph Nader's infamous book, Unsafe at Any Speed. (It wasn't actually all about the Corvair.) In 1965 US government code standardized on the best example which effectively forced manufacturers to follow suit. We humans are really good at familiar patterns or muscle memory.

Differences between automatic shift patterns was eliminated 50 years ago for safety. Why reintroduce this problem?

As an aside of future automobile interfaces, whatever happened to the stupid idea of controlling your car with a joystick like a video arcade game? I like to think someone tried to implement it and discovered how hard it is to control that car and hang on at the same time.

If electric cars signal the transportation future, why bother with this clumsy half-step that confuses the old console shifter with the new reality? Electrical switches don't need much space, move it to an obvious place on the dashboard. Make the entire user experience different enough so as not to be confused with the old way yet intuitive enough that any driver could sit down and immediately understand its operation. E.g., a relative forward motion puts the car in forward mode. Normally I'm a proponent of solidly-located rotary controls like a steering wheel in bouncing, jostling car cabins but don't waste time with other broken interfaces like Mercedes' and other's PRNDL rotary dial. Look forward.

Automatic transmission shifters have been through a number of designs. A PRNDL lever is still the best of them.

Principle of Least Surprise FAIL

Drivers have become acclimated to the shift lever in an automatic transmission since the first such two-pedal automotive user interfaces. It's an interface that still makes perfect sense for controlling a vehicle that has only a single gear; every slot of the traditional PRNDL shift pattern is represented by functionality in the LEAF's return-to-center shifter. Given this exact, 1:1 mapping, why change the interface? Nothing is gained and the possibility of confusing new LEAF drivers or anyone switching between a LEAF and car with a conventional automatic shifter is risked.

Why Is this Important?

Selecting the drive mode is a critical control that affects people in and around a car. The gravity of this action should exceed that of pushing a button to turn on the radio or twisting a knob to turn up the A/C.

Other Return-to-Center Shifters

But wait! I hear you say. There are other shifters that return to center! Yes, my criticism extends to the Toyota Prius, various Fiat-Chrysler products and other such automatic transmission shifters too.

But what about motorcycles, paddle shifters and other sequential shifters? Those are either fully manual transmissions with a significantly different user interface (e.g. clutch pedal or lever) that cannot be confused with a conventional automatic or they are specific performance or even racing applications. Manual gear selection on conventional automatic transmissions is generally achieved with different, compatible motions often within a separate plane or gate from the PRNDL pattern which is still there. They are not the same as the problematic LEAF shifter.

Summary

This isn't hard. The best solution is a lever that stays in position and follows the conventional PRNDL pattern (or PRNDB if you prefer). The best solution is no change at all.

  1. Make it show its state.
  2. Make it clear the action that will be taken.
  3. Make it distinct from less important controls.

Until you come up with something better at all these things than a PRNDL shifter, please just stop. Yes, better because familiarity still counts for a lot.