As recently as last year, the ride between BART’s Glen Park and Balboa Park stations was a screeching cacophony, as the rail system’s old cylindrical wheels scraped on its corrugated rail. Now, that journey is about 20 decibels quieter, Greg Shivy, the principal track engineer, said during a recent presentation to BART’s Board of Directors. The difference, he said, is that between a roaring gas-powered lawn mower and a steadily thrumming dishwasher. BART began shaving about 2 millimeters of metal off every wheel in its fleet two years ago, a simple solution to the head-splitting squeal a train makes as it roars along the track. That project is almost complete.

Source: BART rides getting quieter with repairs to steel wheels – SFChronicle.com