In very slippery road and winter conditions, the 2004-2006 model year Prius with OEM or non-winter tires, the traction control can leave the car unresponsive even with the accelerator pressed to the floor. It does this to prevent useless wheel spinning. Those who live in snowy, winter climates should mount quality ice and snow tires (marked with a snowflake in a mountain) in the winter season. More recent Prius ECUs have an improved traction control system that will 'pulse-spin' the wheels in super slippery, icy conditions.