Woody, a guide dog, stops trainer Sioux Strong in her tracks as a Prius hybrid silently approaches. Advocates for the blind are pushing Congress to pass legislation that would make the cars' electric motor louder, making them easier for those with impaired sight to detect in traffic. (Photo by Thomas Boyd)

PORTLAND, Ore. — Earlier this month, Erin Rumer and her guide dog, Driver, were in downtown Portland when the yellow Lab stopped short, putting his training to use.

Confused, Rumer stopped.

Listened.

And heard the echo of silence as a hybrid car darted past, throwing a wake so quiet the air quivered — and it was gone.

The near miss comes just months after the pair's graduation from a hybrid-traffic training class, which Rumer says raises a red flag: The classes help guide dogs recognize silent dangers, but the blind — as well as other pedestrians and bicyclists — remain at significant risk.