I've read that negative acceleration can mean two things: 1) Something is slowing down 2) Something is speeding up in the opposite direction Can it mean those two things at the same time? So, if I'm driving a car at 30 mph, and then I slow down... how is it that the car is speeding up in the opposite direction? That doesn't seem right. I would agree that it is slowing down, though. Because it would appear that the car is not be negatively displaced. It seems like the real situation is distance traveled is changed. And acceleration denotes the direction of travel. So, negative acceleration in the positive direction is deceleration, but negative acceleration in the opposite direction is basically increasing speed in the opposite direction? Right?