A number of changes have been announced for the Grand National following a safety review, but the field size is to stay at a maximum of 40.
An official inquiry was launched after the deaths of two horses in April.
The start will be moved 90 yards closer to the first fence, while measures will also be taken to stop horses getting caught up in the starting tape.
The Becher's Brook landing zone is being levelled further, while there will be a review of fence designs.
The changes to the start may slow the speed the first fence is approached at, while moving the start further away from the crowd will reduce noise that can distract the horses.
On field size, Aintree Racecourse and the British Horseracing Authority (BHA) said they believe the course and fences can accommodate a maximum of 40 runners, but will "continue to monitor" the issue.
The charity World Horse Welfare, while welcoming most of the changes, said it was disappointed the field size was not being reduced.
Following the review, the start will now be moved forward 90 yards, reducing the race to four miles and three-and-a-half furlongs, from four-and-a-half miles.
In addition, the starter's rostrum will be put in a position that allows a "no-go zone" to stop horses that false start getting on top of the tape.
Jamie Stier, director of race day operations and regulation for the BHA, said: "It is possible that a more controlled environment at the start, along with reducing the distance between the start and the first fence, could have the effect of reducing the early speed of the race. If this were to be the case, it would be an added benefit."
In April's event, Cheltenham Gold Cup winner Synchronised unseated rider Tony McCoy on the way to the starting area and ran loose in a chaotic opening which was delayed and also featured a number of restarts. He later broke his leg in a fall and was put down.
The fence design project at Aintree will last three years and focus on using materials other than the timber and protective rubber padding that make up the central frame at present. Fence heights will remain unchanged.
Becher's Brook will "undergo further levelling of the wider landing zone, correcting the settlement which occurred following work carried out in 2011", according to the review.
The other horse to die in the 2012 race, According to Pete, may have been injured when brought down by On His Own, who could have been unsighted at the fence, or when another horse, Weird Al, collided with him as he got up.
Fences four, five and 13 will also have their landing areas levelled to "smooth out undulations".
Other measures include £100,000 being invested in irrigation to produce "the safest jumping ground possible" and a new bypass and pen around fence four to catch riderless horses.
John Baker, who runs Aintree Racecourse as part of his role as North West regional director for Jockey Club Racecourses, said: "In recent years, we have made significant investments in safety and believe today's announcement demonstrates we will continue to do so whilst preserving the unique character and appeal of the nation's favourite race."
World Horse Welfare chief executive Roly Owers welcomed "Aintree's demonstrated commitment to making the course safer", highlighting the work to fences.
However, he said: "We are disappointed that they have not proposed reducing the size of the field, although we note that they are keeping this under review.
"While there is clearly no magic formula here, changes need to be made to significantly reduce the faller rate which will reduce the number of injuries, fatalities and loose horses which pose risks to themselves and others on the course.
"We believe the single most effective way of doing this is to trial a reduction in the field size - say for three years. "
In April, only 15 of the 40 horses finished the race and the two deaths led to questions about the National's future from animal welfare groups.
Several alterations had been made to the course for 2012 after a previous review following the fatal injuries suffered by Ornais and Dooleys Gate in 2011.
According to the BHA, 20 horses have died in races over Grand National fences since 2001 and 10 have lost their lives in the race itself in the past 12 years.