Olympics-Three-day event safety rules tightened for Beijing

LONDON, June 6 (Reuters) - Safety rules have been tightened for the three-day event at the Beijing Olympics after a number of fatal accidents in the equestrian sport.

From Aug 1, horses and riders will be eliminated after one fall at a fence in the cross-country and showjumping, the International Equestrian Federation (FEI) said on Friday.

According to the current rules, horses are eliminated after one fall while riders are ruled out if they are unseated a second time.

"The reason for the change is firstly medical given the difficulty to evaluate the gravity of a fall which can result in a mild concussion," FEI said in a statement.

"A subsequent lapse in judgment exacerbated by a concussion could result in serious injury."

U.S. Olympic rider Darren Chiacchia was badly injured in a fall at a horse trials in March and was in a coma for 42 days. In August 2006, eventer Sherelle Duke, a friend of British Olympian Zara Phillips, died in a fall in southern England.

The cross-country course for the Olympic three-day event, which will take place in Hong Kong in August, is newly built and largely untested.

Course designer Mike Etherington-Smith, who was also in charge of the course at the Sydney Games, has said his Hong Kong design is more compact than his 2000 Olympic course and "will look spectacular on television". (Writing by Robert Woodward, editing by Miles Evans)