Ms. Ward, who had been riding a pink Trek bicycle, died of major head trauma after colliding with the left side of the truck's cab, Redwood City CHP Officer Art Montiel said in a phone interview. A bicycle helmet was found at the scene.
Ms. Ward had been dragged under the truck and was found under the trailer near its right rear wheels, Mr. Montiel said.
The rig has 26 wheels, 10 for the truck and 16 for the trailer, which was carrying a forklift, Mr. Montiel said. The rig had been heading west from a job site near Sand Hill and Alpine roads, he said.
Both Ms. Ward and the truck had been traveling westbound on the brief straight section of roadway just west of the stop sign at the northbound entrance to I-280.
The truck had been headed to the southbound entry ramp of the freeway, Mr. Montiel said. "For unknown reasons, the two collided," he said. "We're looking for witnesses. We can't seem to put two and two together to make it obvious what happened."
There are three westbound lanes of traffic on Alpine Road as it approaches the southbound ramp: a left and middle lane that merge as they head straight into Ladera and Portola Valley, and the right lane that curves on to the freeway.
As they ride into Ladera, bicyclists traveling west on the right edge of Alpine Road have to negotiate a crossing of the freeway entry lane so as to get to the middle lane and continue west.
It's possible, Mr. Montiel said, that Ms. Ward had crossed the freeway entry lane behind the truck and was beside it on the right edge of the middle lane when she was forced into the truck's side by another vehicle coming up behind her in the middle lane.
The impact point was on the side; the front of the truck was not damaged, Mr. Montiel said.
"Why was she that close?" he wondered. "I'm hoping somebody will call in."
Tests of the truck driver for impairment came up negative, Mr. Montiel said.
The I-280 entry and exit ramps were closed for three hours.
Ms. Ward, a trained nurse, won state Sen. Joe Simitian's "There Oughta Be a Law" contest after suggesting a bill to add a bittering agent to antifreeze so that children and animals would not be accidentally poisoned. The law was passed in 2002 and was introduced as a federal bill by Congressman Gary Ackerman, D-New York, in 2004.
Investigators are asking for witnesses to come forward. Anyone with information is asked to call Officer K. Nielsen at 369-6261.
Sue Dremann of Embarcadero Media contributed to this report.