From https://www.rtands.com/track-maintenance/on-track-maintenance/corrective-and-preventive-rail-grinding/ February 26, 2019

The Bay Area Rapid Transit (BART) system is a pioneer in using acoustic data to guide its corrective grinding program. BART combines acoustic data collected by microphones on the trailing ends of revenue trains with data from a Corrugation Analyzer Trolley to pinpoint locations that need to be ground. BART uses CoreTracker, a proprietary software utilized by ATS Consulting, BART’s acoustics consultant, to look at noise data in a graphical form, and to generates reports that identify priorities based on the decibel level.

“We tend to see roaring corrugation at frequencies between 400 and 600 Hertz,” said Greg Shivy, BART’s principal track engineer – maintenance and engineering. Noise levels, along with complaints from passengers and nearby residents, increase in tunnels and aerial structures, and at speeds above 50 mph.

Like most transit systems, BART gets precious little time for maintenance – about 90 minutes during the week and up to 4 hours on weekends. Near term, much of the grinding effort is spent chasing corrugation. But it has been effective. “We saw a 73 percent reduction in customer noise complaints, last year,” Shivy said.

But addressing hot spots is only one driver of the grinding plan. BART only recently completed a migration of its fleet from a cylindrical wheel shape to a conical BT3 wheel profile. New “interim” rail profiles have been designed and applied to correspond with the changing wheel shapes. Using a pair of 12-stone in-house transit grinders, BART plans to grind nearly 4,000 pass miles across the 125-route-mile system to achieve the desired rail profile over a four-year period.

About 1,000 pass miles were completed last year. And by the end of this year, BART will have completed the interim rail profile across the system. It will then go back and install the final profile.

With all the wheels converted to the new cylindrical profile as of January of this year, BART start with a clean slate. “We’re going to look closely at corrugation growth rates to see how they correlate to curve radius, speed and track types,” Shivy said. “It will be interesting to see how corrugation growth rates change with the new wheel and rail profiles over time.”

And with the corrugation issues on the run, BART will be able to get its grinders over the system more quickly with less metal removal to address RCF and other surface conditions. A more efficient grinding program coupled with comprehensive pre- and post-grind measurement of surface conditions will go a long way toward improving conditions at BART and educating the industry, overall.

“The ability to measure rail profile, wear, surface cracks, and corrugation is enabling us to take a more scientific approach to rail grinding,” said Gordon Bachinsky, president of Advanced Rail Management Corp., which manages BART’s rail measurement and grinding programs. Monitoring noise levels, as is done at BART, will not only identify problem areas, but verify that they’ve been addressed, he said. “These improvements, along with more rigorous requirements for surface finish, will push grinding, and possibly milling, into an exciting new era.”