One feature of electric vehicles we hear a lot about is regenerative braking. Normally, the battery sends electrical power to the motor, turns the wheels, and sends you down the road. Regenerative braking effectively puts this system into reverse, harnessing the rotation of your wheels to turn the motor into a generator, sending power back to the battery and recharging it. Anyone who’s ridden a bicycle with a small generator to power the lights has experienced how much extra drag even a couple of light bulbs can put on the drive system. It’s far from a perpetual motion machine, but any energy an EV can recover and put back into the battery to extend its range is a benefit.
However, this presents another problem. Since regenerative braking does not use the vehicle’s standard braking system, the brake lights don’t need to be turned on, despite the significant amount of deceleration regenerative braking can provide. This came to light in a video by Technology Connections that demonstrated this issue on his Hyundai Ioniq 5, which could use regenerative braking to aggressively slow almost to a stop before turning on its brake lights. While the American Federal Motor Vehicle Safety Standards do not require EVs to light up the brake lights under regenerative braking, they explicitly do not prohibit it, either.
Consumer Reports picked up this story in June 2023 and brought it to an even larger audience than the original video. In response, Hyundai/Genesis and Kia told Consumer Reports they would implement a solution for this issue later that summer. Both Hyundai and Kia followed through and made this update available in August.
With EVs proliferating like bunnies these days, that still leaves the vast majority of them that could potentially have this problem. This is a danger for anyone following an EV, but particularly for motorcycles, which have much more to lose than a car by running into a rapidly decelerating car without brake lights. Even worse, there seems to be no consistency in whether any given EV will turn on the brake lights under regenerative braking. Tesla, for example, says:
If regenerative braking is aggressively slowingModel Y(such as when your foot is completely off the accelerator pedal at highway speeds), the brake lights turn on to alert others that you are slowing down.
This shows that Tesla has considered this scenario and programmed some good behavior, but it’s still unclear exactly at what point the brake lights turn on while you slow down. A car’s standard braking system errs on the side of caution, turning them on any time the brake is applied, regardless of whether it is gentle or hard. No such standard currently exists for regenerative braking. Without that standard, EV manufacturers can do whatever they want, from turning brake lights on under even light regenerative braking to not turning them on at all unless the brake pedal is pressed.
What about electric motorcycles?
Electric motorcycles are not nearly as common as electric cars at this point, but someday they may be. Their capabilities are impressive, their range is improving, and charging infrastructure will only get better. Like their four-wheeled cousins, electric motorcycles also use regenerative braking, which opens us up to being on the receiving end of a crash by an inattentive driver who didn’t notice we were slowing down because our brake lights weren’t on.
When I took a quick demo ride on the Zero DSR/X, one of my favorite features was Canyon mode. This unleashes the bike’s full performance capabilities of Sport mode yet adds Eco mode’s full regenerative braking capabilities. The end result was like riding a gas-powered motorcycle with strong engine braking. Particularly on the off-road course I rode, regenerative braking was powerful enough that I barely used the actual brakes at all. It was easy to modulate the throttle and simply roll off when I needed to slow down. This could also be useful on the street when carving corners through the canyons — hence, the name for this mode. However, like the Hyundai shown in the video, the brake light won’t necessarily turn on when using regenerative braking to slow down. My personal observations indicate that Zeros do not light up the brake light under regenerative braking.
We contacted Zero, as well as LiveWire, for any comments on this issue from the manufacturer’s point of view. LiveWire did not respond, but Zero provided the following statement:
There have been regulatory factors at play outside of Zero’s control. The evolution of motorcycle regulations generally lags behind that of car regulations. At Zero we’re proactive in monitoring upcoming changes and actively participate with the development of new regulations through our involvement with regulatory committees. We’re unable to comment on specific timelines, but we release new features on a schedule that balances the timelines of regulatory acceptance and technological development.
Indeed, even car regulations tend to lag behind developing technology. Look no further than the controversy over Tesla’s Full Self Driving mode for proof of that. It is no surprise that regulations for cars take even more time to trickle down to motorcycles.
However, electric motorcycle manufacturers could take it upon themselves to be proactive and address this situation before regulations force them to. I’m not singling out Zero on this. Their electric motorcycles are the ones I have the most experience with, but this applies to LiveWire and all others. Everything on these bikes is already computerized anyway. All it would take is a little bit of programming to say that when regenerative braking exceeds a certain amount, the brake light should turn on. This is exactly the fix that Hyundai and Kia have already applied, again through a simple programming change.
Photo: Justin Hughes
Until or unless such a change is made, we, as riders, can make a small change in our behavior to ensure our safety when using heavy regenerative braking. It may not be necessary for braking purposes, but a light tap or drag on either brake will manually turn on the brake light, letting anyone behind us know we are slowing down. This is likely the preferred riding technique anyway, but now has an additional safety aspect from the lighting and visibility perspective.
