TTC says no definitive cause of issue behind intense subway vibrations after lengthy investigation

After months of complaints from residents along the Toronto Transit Commission‘s Line 2 subway line in the latter part of 2018 and the beginning of 2019, the agency says it still hasn’t determined what’s definitively behind the source of the issue behind intense, extraordinary vibrations.

Global News has reported on the issue since October. Throughout that time, the TTC has said the vibrations and an associated clunking noise heard and felt by residents on parts of the Bloor-Danforth line are being caused by “wheel flats,” which are flat spots developing on subway car wheels. On parts of the system, mechanical lubricators are used on sections of rail to help minimize squealing from wheels. However, between turning off the units for testing and malfunctions in equipment, complaints were made about excessively loud screeches.

In a report being considered by the TTC board on Wednesday, agency staff noted it’s normal to see an increase during the autumn periods due to falling leaves and “seeping natural oils” that reduce friction and increase train sliding during braking. Wet weather, emergency braking, onboard computer braking software and material composition of the wheels have all been cited as contributors to “wheel flats.”

However, staff acknowledged they received an “unusually high” number of complaints about issues related to “wheel flats” in September and December.

“These two incidents overwhelmed the maintenance facility and corrective maintenance activities were no longer able to keep pace with the high volume of new wheel flats being generated each day,” the report said, noting the issued carried into this year.

“The number of new wheel flats continued to remain high throughout January and February 2019. Given the large backlog of flats experienced, to ensure subway service requirements were met, trains had to be placed into service with this defect.”

The problem forced the TTC to turn to engineering experts at the National Research Council of Canada (NRCC) in January and a rail consulting firm in May to probe the issue. The report said TTC staff, the NRCC and the consultants reviewed train and track data, inspected vehicles and track equipment, did a “systematic elimination of potential contributors to the problem” and looked at how other agencies responded to similar issues with “wheel flats.”

The TTC said after speaking with multiple transit agencies in the United States, many of which noted seasonal “wheel flat” issues, “staff at each location could not recall having wheel flat issues similar to the problem faced at the TTC.”

After reviewing the track data, the report said, “Patterns in wheel flat locations however was difficult to identify. Wheel flats appeared on both sides of the trains and were not consistent from axle to axle. Geographical location of wheel flats being generated along Line 2 could also not be determined.” Also, inspections and tests of train cars “did not identify deficiencies that would contribute to the wheel flat problem.”

READ MORE: TTC says it’s trying to rectify Line 2 noise issues in west end

As part of the review, the TTC said speed restriction zones have been put in place in open portions of the subway line during inclement weather to minimize wheel slipping. Also, staff said they have modified how the rail lubricators work and are testing new technology. Despite temporarily turning the lubricators off and temporary speed restrictions in outdoor portions, there was only a minor reduction in “wheel flats” during the test period.

The report noted the NRCC gave the TTC “action items to reduce formation of flats,” but the full list of recommendations from the organization wasn’t included in the TTC report.

The transit agency said there has been a noticeable improvement recently, coinciding with spring and summer seasons.

“With a recent seasonal reduction in new wheel flats being created, the effects of wheel flats on noise and vibration on Line 2 has been nearly restored to historically normal amounts,” the report said.

“Staff will continue to work with the National Research Council of Canada to investigate this problem and to improve operations to better avoid future unexpected spikes in wheel flats.”

There is a recommendation for TTC staff to report back to the board by the end of March on the status of the “wheel flats” issue and “results, conclusions and lessons learned” as part of the agency’s ongoing investigation into the issue.