“The brakes worked,” said Dar to the assembled School Board members and CHP patrolmen. “There was no brake warning light. No smoke or smell of burning brake linings.”

He explained what had happened on the day of the accident.

The bus driver had left the national forest campsite with both of her emergency parking brakes set. After the first downhill stretch where they could smell the brakes burning, the next two miles had been uphill. “Brakes give off an odor,” explained Dar, “when the brake drum and shoes reach temperatures above approximately 600 degrees Fahrenheit.” The teachers, students, and driver had smelled the burning odor during both the first couple of downhill and uphill miles on the return journey. The driver had ignored the smell.

The brake warning light had gone off briefly and then started blinking again as the bus approached the top of the last rise before the long descent toward Borrega Springs. The surviving teacher, sitting in the first row on the right side, had seen it blinking.

“There’s only one engineering explanation for the brake warning light to signal brake overheating during this portion of the trip,” said Dar. “The emergency brakes had been applied continuously from the time the bus had left the campsite parking lot.” In addition, he explained, the surviving passengers told of the bus “handling poorly” and “surging slightly” during the first two uphill miles of the trip. The driver had ignored all of these warning signs and had begun the long, downhill section of the canyon road.

Dar explained that on the day of the accident, he had noted that the front wheels of the bus were freewheeling but that the rear wheels were locked. He explained further that this type of bus had automatic brakes that would be applied without driver input when air pressure in the system drops below 30 pounds per square inch. The locked rear wheels had told him that low air pressure in the brake system had caused the automatic brakes to be applied, and their Safety Board tests had shown that the system had not leaked and that the air compressor was sound. But the automatic brakes could not stop the bus because they had been overheated prior to their application.