Mary Keitany was back where she prefers to be Sunday in the New York City Marathon — far, far ahead of everyone else. Keitany, an Olympian from Kenya, took off alone in the race’s second half and finished more than three minutes ahead of her challengers, with a time of 2 hours 22 minutes 48 seconds. It was her fourth victory here, and the second fastest race any woman has run on this course.

It started out typically enough. For the first half of the race, Keitany, 36, tucked into a pack of about 24 women, including some of the top talent in this event. Keeping her stride loose, Keitany looked like just another jogger — albeit, a pretty fast one — as she made her way through the early stages.

Once she reached Manhattan, though, there was a race to run.

Soon out of view of her closest opponent, Keitany tore through the second half of the marathon in 1:06:58, a time few women in the field had achieved. It was about nine minutes faster than her first half, and she never wavered as she ground toward the finish.