Witnesses said the woman who had been riding a rented bicycle, appeared to lose control of the bicycle and crossed a double yellow line into oncoming traffic on a steep curb at the 7,000-foot level. She then attempted to set the bicycle down on the pavement in front of the upward-bound tour van.

The oncoming van, belonging to another bicycle tour company, apparently tried to stop but struck the woman at about 10 a.m., park officials said.

Park rangers responded with life-support equipment and arrived to find a doctor from one of the bike tours tending to the woman. Rangers administered oxygen, park officials said. The rangers performed cardiopulmonary resuscitation until an ambulance arrived and paramedics took over.

The woman was pronounced dead at the scene between 10:45 and 11 a.m., park officials said.

Traffic was stopped in both directions and the road remained closed into the afternoon. The Maui County Fire Department responded with a fire truck and a helicopter.

"This is a sad day for everyone," said park superintendent Marilyn H. Parris. "But I am very proud of the level of response from the park and the cooperation of all the supporting agencies involved."

A chaplain familiar with critical incident stress is on scene to help everyone involved, park officials said.