In case you are wondering about aggressive regen and notifying drivers behind you of your deceleration via brake lights, don't worry because AC Propulsion has already figured this out. Their motor control samples motor speed at something like 10Hz, and since the motor drives through a fixed ratio, motor speed is an unambiguous indicator of vehicle speed. So, by continually sampling speed one knows when the car is slowing down, and the brake lights are turned on automatically if the deceleration exceeds a low threshold. It works in reverse too. The brake lights also come on with actuation of the brake pedal as in a normal car. Interestingly, you can be using quite strong regen holding speed steady on a downhill and the brake light will not come on.
My question: will the Nissan Leaf boast a similar feature?