Believe it or not, there’s a precise answer to that question.100 feet. VTL section 1163(b) specifies that: “A signal of intention to turn left or right when required shall be given continuously during not less than the one one hundred feet traveled by the vehicle before turning.”
What does this mean?
If you’re making a turn, you must utilize your turn signal at least 100 feet before the location where you plan to turn. Your turn signal must be “given continuously,” meaning that you have to keep the blinker in use from this 100-foot threshold until you complete the turn.
As a practical matter, is this a legal defense in court?
Maybe. There are judges who may want the officer to be precise in this testimony. Technically, the statute doesn’t require signaling at all before the 100-foot mark. That said, you’re not likely to win an argument with the police officer if you say that you began signaling at 100 feet, when he says you didn’t start until 50 feet. Still, these are the kinds of technicalities that attorneys often use to win cases. Failure to signal is a two-point violation, and in the TVB courts of New York City, the only way to avoid those points is to go to trial and win.