Insufficient Brake Light Alerts on Select Electric Vehicles

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June 12, 2023
Edward Smith

Limited Brake Light Notifications on Certain Electric Cars

A significant safety concern may affect thousands of electric vehicles currently operating on American roads. This issue pertains to the brake lights of these vehicles, which may fail to light up when the vehicle stops during the aggressive-regenerative braking settings. Regenerative braking is a feature that allows an electric vehicle to slow down or brake while simultaneously recovering energy and channeling it back into the battery for recharging.

In numerous electric vehicles, the regenerative braking settings can be adjusted to an intense level called “one-pedal driving.” This setting enables the vehicle to decelerate rapidly and even come to a complete stop without the driver needing to engage the physical brake pedal. The vehicle accelerates by pressing the accelerator pedal in these vehicles, similar to conventional cars. However, even the slightest pressure release on the accelerator pedal initiates a rapid deceleration, akin to pressing the brake pedal in a traditional vehicle. Numerous drivers who use the one-pedal driving feature prefer to maintain gentle pressure on the accelerator pedal while slowing down, thereby ensuring better transitions between acceleration and deceleration.

Specific Models with Brake Light Issues

Consumer Reports evaluated over a dozen electric vehicles in its fleet, revealing a concerning issue related to the brake lights of specific models from Kia, Hyundai, and Genesis. During one-pedal driving, these vehicles fail to illuminate their brake lights unless the driver fully releases the accelerator pedal. This results in a lack of warning for vehicles behind them regarding their rapid deceleration. In contrast, other electric vehicles tested did activate their brake lights, highlighting the availability of technology to avoid confusion for following drivers in this regenerative braking mode.

Consumer Reports identified this issue in 2014 with the BMW i3, which resurfaced recently through a popular YouTube video posted by the Technology Connections channel. The video, which has amassed approximately 2 million views, showcases how the 2022 Hyundai Ioniq 5 can rapidly come to a near-complete stop without the brake lights ever activating when using the car’s i-Pedal, its regenerative-braking mode. The brake lights only illuminate if the driver removes their foot from the accelerator pedal. Maintaining some pressure on the accelerator pedal during the deceleration process makes it possible to bring the vehicle to a near-complete stop without the brake lights ever indicating the action.

Consumer Reports Tests Spark Concerns

Consumer Reports’ team of automotive experts conducted a comprehensive analysis following the Ioniq 5 report to assess the extent of the issue across various brands and models. They tested the behavior of brake lights on all 24 electric vehicles in their fleet, which were purchased explicitly for the auto-test program.

The engineers at Consumer Reports measured the rate at which each vehicle decelerated while using the regenerative braking modes, commonly known as one-pedal driving. They also observed the point at which the brake lights were activated in response to deceleration. On average, most EVs’ brake lights illuminated when the regenerative braking system reduced the vehicle’s speed by approximately 0.1g (g-force). This level of slight deceleration was considered significant enough to warrant informing other drivers by activating the car’s brake lights.

Although most EVs properly illuminated their brake lights during intense regenerative braking, a few vehicles stood out for their notably aggressive deceleration levels. These vehicles include:

  • 2022 Hyundai Ioniq 5 SEL AWD
  • 2022 Kia EV6 Wind AWD
  • 2023 Genesis Electrified GV70
  • 2023 Genesis GV60 Advanced
  • 2023 Kia Niro EV Wind

Lack of Brake Light Activation During Braking

When the Hyundai Ioniq 5 undergoes rapid deceleration using regenerative braking, its brake lights fail to illuminate, neglecting to inform other drivers of the car’s slowing down. These lights only activate once the vehicle has nearly come to a complete stop. However, this potential safety hazard does not exist in CR’s 2023 Hyundai Ioniq 6 SEL AWD test vehicle, as it consistently exhibits proper brake light illumination while slowing down in its i-Pedal mode, even if the driver maintains some pressure on the accelerator pedal.

Hyundai, Kia, and Genesis EVs allow the driver to adjust regenerative braking levels on the go using paddles behind the steering wheel. According to CR’s engineers, even in the less aggressive modes that do not support one-pedal driving, the driver still benefits from the full regenerative braking capabilities since EVs are designed to utilize regenerative braking to the maximum extent before the system automatically incorporates power from the conventional friction brakes.

The government lacks a clear standard for deceleration levels that would activate brake lights, despite the safety hazard of brake lights failing to illuminate during one-pedal driving. According to the Federal Motor Vehicle Safety Standard, the stop lamps on every vehicle must be activated when the service brakes are applied. When the service brakes are not applied, the standard does not require the stop lamps to be activated. Simultaneously, the standard does not forbid the discretionary activation of the stop lamps when an alternative system is responsible for slowing down the vehicle.

It should be noted that the brake lights also don’t illuminate when the driver of a conventional vehicle with a manual transmission downshifts a gear or two to help slow the vehicle. Furthermore, to reduce speed, the brake lights do not illuminate when downshifting a vehicle equipped with an automatic transmission, whether done through the gear selector or the steering-wheel paddle shifters.

Issues With Mercedes EVs

Consumer Reports encountered an additional safety concern while testing electric Mercedes vehicles’ brake lights. Upon activation of the one-pedal driving (Strong recuperation regenerative braking mode), the brake lights of the tested vehicles deactivate as the vehicle stops. In the beginning, as the driver releases the pedal, the brakes light up when the deceleration reaches approximately 0.15g. However, as the speed decreases to around 5 mph and the vehicle adjusts its deceleration rate to ensure a smoother stop, the brake lights abruptly switch off. They remain off for over 15 seconds, even after the vehicle has stopped, before automatically illuminating again after approximately 15 seconds.

The vehicles displaying this behavior were all acquired as part of Consumer Reports’ regular testing program and include:

  • 2023 Mercedes-Benz EQE SUV 350 4Matic
  • 2022 Mercedes-Benz EQS 580 4Matic
  • 2023 Mercedes-Benz EQE 350 4Matic sedan
  • 2023 Mercedes-Benz EQS SUV 450 4Matic

To avoid the problem, Consumer Reports advises drivers of the impacted Mercedes-Benz models to only use the normal and No Recuperation modes. However, if a driver insists on using the Strong Recuperation mode, CR suggests they press and hold the brake pedal once the vehicle reaches a complete stop.

The YouTube video below explains the issues with electric vehicles’ brake lights.

Northern California Personal Injury Attorney

I’m Ed Smith, a California Personal Injury Lawyer. If you were hurt in an accident and need legal guidance, call our law firm today at (916) 921-6400 or (800) 404-5400 for free, friendly advice.

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Photo by Ed Harvey on Unsplash

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