Discription of Events: suddenly started slowing down the car at significant rate and I kept needing to slam the breaks at least good 20 times. Suddenly stopped the car and opened the door on Route 9 and started cursing loudly. Kept opening window to swear racial slurs. She was a white women in little over middle age. everytime there is traffic stop, she would put her car on reverse and back up closer to my car while screaming explicit language. This went on for good 20 minutes on route 9 from Natick to Newton.