The first fence at Aintree will also be moved 60 yards closer to the beginning and a standing start will be introduced in an attempt to reduce speeds at the first hurdle - which had risen to some 35mph on average.
Other changes include reducing the height of 11th fence - which had an unusually high ratio of fallers compared to others - by two inches, changes to the alignment of the running rail on the inside of the course to help catch loose horses, bringing forward the start time to make use of safer conditions, and no more pre-race handler parades.
One horse died at this year's Grand National, which was also marred by delays due to animal rights activists.
There have been five horse deaths from 395 runners in the 10 Grand Nationals raced since changes were introduced in 2012 after a safety review.
Emma Slawinski, director at the RSPCA, welcomed the new steps but warned more could be done.
"We look forward to seeing this announcement pave the way for further changes," she said.
Nevin Truesdale, chief executive of Aintree owners the Jockey Club, said the changes were part of the organisation's "relentless focus on welfare".
