Race organizers, citing “a sense of urgency,’’ unveiled the new rules four months after registration for the 2011 event closed in a record 8 hours and 3 minutes. The registration crisis denied access to the world’s premier marathon for thousands of qualified runners for the first time.

“For us to tell people there was no room for them was a very bitter pill for us,’’ said Thomas Grilk, executive director of the Boston Athletic Association, which manages the event. “We do not ever want to do that again.’’

The new registration policy is aimed at guaranteeing entry to the fastest marathoners through a rolling, online admissions process that permits top qualifiers to register first.