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Comment by oh_sigh | Hacker News Reader

I can go from 75 to 5 mph in my ICE with the brake lights never coming on. Or, I can maintain 75 mph with my brake lights on 100% of the time.

But really, there should just be a standard - it seems obvious and easy for EVs to get it right: If deceleration is > X m/s^2, then brake lights are on.

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The European Union has a regulation that requires EVs to illuminate their brake lights anytime the regenerative-braking system’s deceleration rate exceeds 1.3 meters per second squared, or about 0.13 g.

Cool. How did you know this incredibly specific value? Assuming that it is correct, how was it determined? I would like to learn more.

Simply because I've been driving TVs for a while and "in the beginning" when there was no rules for brake lights to be turned on when regenerative breaking, I got into trouble (German highways) with cars driving behind me and not being able to anticipate / react fast enough when I used it.

I quickly learned to force the break lights and started to follow this issue closely. That's how I became aware of the number.

How the EU saddled for 1.3 and not 1.2 or 1.4 is beyond my knowledge.

Unless I downshift using paddles, my ICE will coast forever from 75. My PHEV, on the other hand, will slow down much faster. I want my PHEV to illuminate the brake lights if I'm decelerating above a certain rate, just as you suggest.

It never occurred to me that I might want my ICE to do the same, but I suppose it would be helpful if I'm heading downhill and downshift without touching the brake.

How will we then be able to tell which drivers are ignorantly riding their brakes all the way down a long hill, versus the drivers using engine braking?

By listening? Engine braking makes noise, which is why it’s banned in some areas.

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