"Many people might be surprised to learn that hanging, when carried out with modern techniques, can be one of the quickest and most painless ways to be executed. The modern method of judicial hanging is called the long drop.In the long drop, those planning the execution calculate the drop distance required to break the subject's neck based on his or her weight, height and build. They typically aim to get the body moving quickly enough after the trap door opens to produce between 1,000 and 1,250 foot-pounds of torque on the neck when the noose jerks tight. This distance can be anywhere from 5 to 9 feet (1.5 to 2.7 meters). With the knot of the noose placed at the left side of the subject's neck, under the jaw, the jolt to the neck at the end of the drop is enough to break or dislocate a neck bone called the axis, which in turn should sever the spinal cord. In some cases, the hangman jerks up on the rope at the precise moment when the drop is ending in order to facilitate the breakage. This is the ideal situation in a long drop. When the neck breaks and severs the spine, blood pressure drops down to nothing in about a second, and the subject loses consciousness. Brain death then takes several minutes to occur, and complete death can take more than 15 or 20 minutes, but the person at the end of the rope most likely can't feel or experience any of it."
More effective than lethal injection.
https://health.howstuffworks.com/diseases-conditions/death-dying/death-by-hanging.htm