Lorraine Explains: One-pedal driving presents more EV kinks to work out

Article content

Consumer Reports revealed last week that some models of EVs, when operating in the most aggressive setting of regenerative braking, are not engaging their brake light system if the driver’s foot is not fully off the accelerator.

Article content

Just when I thought I was out, they pull me back in. It took decades to get regulators to finally accept that too many vehicles on our roads with daytime running lights were not adequately lighted, and then make necessary changes. The smaller front lighting system left too many drivers with a dark rear-end, most fooled because they were staring at a fully illuminated dash. We will face years and years of overlap with drivers still not understanding how dangerous it is to be unseen by those following. Here we go again.

The report highlights the problem they discovered on the following vehicles:

Article content

What is one-pedal driving?

It’s the result of something called one-pedal driving; each manufacturer calls it something different, for Kia, Hyundai and Genesis it’s called i-Pedal, Nissan calls it e-Pedal, and some simply have a button or setting with a symbol. The setting allows a driver to recapture as much electricity as possible to return it to the vehicle. Braking produces a lot of energy, and in internal combustion engine vehicles, it’s lost to heat through brake pads. EVs already recapture that energy, and one-pedal driving allows them to do so even more aggressively. From The Drive, “in [one] study, scientists found that one-pedal driving recaptured up to 26% of decelerated kinetic energy, extending the range in some models by a whopping 62 km (38 miles).”

Article content

If you let up on the accelerator in an ICE vehicle, the vehicle will coast; coasting saves fuel. In contrast, when you apply the brakes in an EV, you are recapturing energy — that would otherwise would go to waste — and extending your range. One-pedal braking goes one step further: if you are not actively accelerating, the car is braking.

Do brake lights work with one-pedal driving?

It’s a weird sensation at first, but once you realize what the car is doing, many become advocates. With a little practice, you can pilot your car while rarely having to actually apply the brake yourself — hence, one pedal. This is actually where the problem is arising. In order to make this a smooth transition, many drivers, even when they’ve chosen the i-Pedal or aggressive braking mode, keep their foot lightly on the accelerator. It’s the best of both worlds: full retrieval of energy that might otherwise be lost and a smooth ride. Who doesn’t want to extend their valuable range?

Article content

Except.

That Consumer Report discovery highlights an important issue on our roads. Driving is a team sport, and you are responsible for keeping your vehicle in safe running order, for driving it responsibly, and for making your intentions known to other road users. The absence of brake lights while your vehicle is aggressively slowing down is dangerous. 

If you’ve driven a car with a manual transmission, you know you can engine brake by gearing down. Brakes usually last longer in a manual for this reason. But any good instructor will also have told you that you still have to tap your brakes as you’re gearing down because otherwise, you are just another unpredictable idiot that nobody can trust. The problem for manufacturers, or at least the challenge, is to remove as many hurdles as possible between idiots and other drivers. I’m aware you can lead a driver to a turn signal, but you can’t make him blink. But you still have to have indicators.

Article content

The video on the Consumer Report piece is insightful. A vehicle traveling over 40 km/h is brought to a stop by i-Pedal with no indication from the outside that it is stopping. Most drivers are familiar with the coasting of ICE vehicles, especially in stop-and-go traffic, but deliberate braking — not coasting — requires that action to be signalled to others on the road.

If a car ahead of you begins firmly slowing down and you have no warnings about what is happening, you’re at the beginning of what could be a deadly chain reaction, especially if that car then accelerates, leading to more questions. Did the brake lights fail? Did the car cut out? Did the driver do that on purpose?

Consumer Reports purchases all its own vehicles for testing, which means there could be additional models these problems apply to, but also noted a concern in the course of its testing with the Strong Recuperation mode (one pedal braking) on a handful of Mercedes-Benz EVs. “…the brake lights on the vehicles we tested turn off as the vehicle comes to a complete stop. Initially, after the driver steps off the accelerator pedal in Strong Recuperation mode, the brake lights illuminate when deceleration reaches about 0.15g. Then, as the speed drops down to about 5 mph—and as the vehicle reduces its deceleration rate to smooth out the stop—the brake lights suddenly turn off.” The test crew believes the length of time the brake lights are not illuminated — 15 seconds — is unsafe. 

All of these things are highly fixable, and indicative of the rapidly advancing technology manufacturers are putting out. Hyundai (and Genesis and Kia) might be tempted to say, “don’t keep your foot on the accelerator when you’re in i-Pedal” but that’s not a fix. If a preponderance of people are using your technology in a way that makes it unsafe, it’s on you to change that.