Full self driving (supervised) was active and functioning properly on interstate 70. The self-driving feature decided to move one lane over to the furthermost lane to the left. That lane was half covered with snow. The speed was approximately 65MPH When the front left wheel hit the snow the the car swerved to the right and hit the snow bank against the rail. I immediately steered to the right and could limit the damage Damage was not severe and I could drive the car to destination