Electric vehicles use regenerative braking to harness kinetic energy and return power to the battery. Most electric vehicles have several levels of regenerative braking from virtually nothing up to what feels like pressing the brake pedal moderately.
Some electric vehicles have a mode that enables a driver to drive almost without ever touching the brake pedal at all. This is generically called one-pedal driving, although has different terms in different vehicles, e.g. i-Pedal in a Hyundai Ioniq 5. The driver can turn the mode on and off at will.
When the driver pushes the accelerator, the car accelerates, as per normal. However, when the driver lifts off the accelerator, a high level of regenerative braking is applied by varying the magnetic resistance in the electric motor. The driver can modulate the amount of braking by lifting off more or less. If the driver lifts off fully, the maximum level of regenerative braking is applied and the vehicle will come to a stop (unless regular regenerative braking which usually leaves the car able to continue to creep forwards at around 5km/h).
The brake lights illuminate during one-pedal driving to make drivers following you aware that you’re slowing down.
This takes some acclimatisation on the part of the driver, and there’s a risk that the driver may become accustomed to not using the brake pedal, and therefore be slower at reacting in a real emergency (one-pedal braking won’t perform an emergency stop unless you also have autonomous emergency braking in your vehicle). No studies have been done on this so far.
One pedal braking also means less coasting, and when you initially start using it, you may find it difficult to deliver a smooth drive for your passengers.
The benefit of one-pedal braking is more energy recaptured, and less wear and tear on your service brakes (i.e. your regular brakes); this means less brake dust in the air and on your shiny alloy wheels. The slowing down part of one-pedal braking is very smooth. The disadvantages of one-pedal braking are the time taken to master a smooth ride (it’s possible you’ll be using more power initially as you learn its characteristics), and potentially getting out of the habit of using the brake pedal in an emergency.
If your EV supports one-pedal braking it’s important you get EV training so that you maximise the features and the range.