Technically probably one mile over, I do not know if there is a consensus in New Jersey or elsewhere, maybe there is. In the 18 plus years that I have been handling speeding tickets and other municipal Court matters I have never seen anyone incarcerated for a mere speeding ticket. Generally there is a Threshold regarding suspension of a person's driving privileges. Generally if you are traveling thirty miles over and/or more likely if the person is clocked at 90 or higher there is often a higher chance that a Judge will suspend a persons License or the prosecutor may request one. I have represented people on tickets where they were alleged to have been traveling as fast as 106 in a 65 five and the person received a suspension but was not incarcerated and I was able to lower the points. It depend on the Judge and the facts. I was in a Court where a Motorist was charged with allegedly traveling 123 in a 55 or 65 (I do not recall) and he received a fairly long suspension and a stern warning from the Judge and he was not incarcerated. If you crash a car at a high rate of speed and kill someone, then you have most likely opened the door to a Jail cell if the person is charged with a criminal charge for acting recklessly. I would not recommend speeding to test your proposed theory because it is really worth testing how fast you need to go to push a Judge into considering jail time. I was also in a Court where a young kid was alleged to have been traveling 141 in a 55, I did not hang around to learn the final outcome, but I know that his lawyer was concerned. Everything depends on the facts, were you on the highway, were on a residential street with children present, The statute permits a Judge to put you in jail for speeding, also just because I have not seen it does mean it doesn t happen depending on the situation, but it is an extreme penalty where the only offense the person is charged with is speeding. I hope that helps, feel free to call with any other questions. (201)-342-5030