My all electric has a b mode to shift in. simply put it engages the generator fully when you let off the gas pedal so you can generate electricity. however, when you do this the car brakes quite quick, so quick in fact they call this type of driving one pedal driving due to the fact you very seldom touch the break except for a full stop. the problem is the break lights don't go on unless you put your foot on the break. my concern is the car behind me. if he is not paying attention and does not realize i am slowing down at such a rapid clip bad things can happen, its almost the same as having defective brake lights. my recommendation is to have the break lights come on when you foot is fully off the gas pedal to avoid and rear end collisions for all cars that have this feature. thank you