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Closeup of a BART train wheel on a track.

‘Next rainy season it’s going to be much better’: BART fixes wheel problem that caused delays

on September 3, 2023

Andrew Guzman was late for work nearly every other day last winter. During the monthslong deluge that soaked the Bay Area, his train to the downtown Berkeley BART station was often delayed. Frustrated, he clocked in late to work shift after shift.

“It shows that you’re not reliable. It reflects back on you, even though it wasn’t your intention to be late,” Guzman said. 

Sarah Linn usually gets to work 30 minutes early, but last winter, she was late five times because of BART. She became so frustrated with the service, she considered not paying the fare.

“Why are we paying for this?” Linn asked. “Things are always late and breaking down.” 

The delays and cancellations to BART’s regular service were extensive, affecting thousands of riders on several lines. From January to March, 9,709 trains were delayed due to the weather, accounting for more than half of all the trains delayed. Trips also took longer, with rain forcing speed reductions to the point that only slightly more than half of the trains reached their destinations on time, according to BART’s latest quarterly report

Last winter’s service was “historically poor by our standards,” said James Allison, BART’s media relations manager. 

The winter was historical weatherwise as well, as around 30 inches of rain drenched the Bay Area, inundating roads and the BART system. If this winter packs the same punch, BART says it will be better prepared after working on fixes for months, and riders will experience fewer delays. 

The biggest problem last winter was that wet weather led to wheel spots or wheel flats, which can occur during braking and force a car out of service. Though wheel spots occurred more frequently on the newer Fleet of the Future cars, the root cause of last season’s problems wasn’t the cars themselves, but the complexity of BART’s control system, Allison said. BART has since corrected the control system errors which caused wheel spots. 

However, BART‘s project to replace the 50-year-old, unpredictable control system software is still a decade off. BART and its riders are depending on the transit system’s short-term fixes to avoid another chaotic season. Riders need reliable service just as BART, after years of declining ridership and revenue, needs to keep those riders scanning their clipper cards this winter. 

Ridership was down significantly in January, with 20% fewer riders than BART had projected. And that projection was conservative – 57% less than pre-pandemic levels. BART is using federal emergency funds to make up for budget shortfalls, but those funds will run out in 2025. If riders don’t return or new funding is not secured, devastating cuts will come, BART has said.

What went wrong?

Ultimately, what went wrong in the rainy months was that there were too few cars, Allison said. More trains were taken out of service for maintenance because of the large number of wheel spots. 

Closeup of a BART wheel on a track with a smooth, shaved metal wheel spot
A BART wheel flat (Xueer Lu)

Water on the track reduces the friction between the wheels and the rail, and the wheels can lose their grip, slipping and spinning rapidly in wet conditions. Because trains are on a fixed track and not at risk of spinning out like a car, BART’s control system usually slows the train down in the rain. 

However, that wasn’t what happened during the weeks of extreme rainfall. When the wheels started to spin rapidly on the waterlogged track, the control system misunderstood why they were spinning faster. It automatically activated the emergency brake, as it would if the train was dangerously speeding up. When the emergency brake locks the wheels in place and the train slows to a halt, the jammed wheels grind against the track, shearing off layers of metal.

Those problems occurred on BART trains on eight sections of track — south of Concord Station, between Walnut Creek and Lafayette, between Pleasant Hill and Concord, between Dublin and the Hayward Maintenance Complex, north of Warm Springs station, at Lake Merritt station, Bay Point station, and north of Bay Point Station. 

In other instances, software errors issued incorrect speed codes to trains on those eight sections, causing the wheels to slip and bump against the track, which also contributed to wheel spots. 

There were so many wheel spots from the rain that BART mechanics were fixing train wheels one car at a time, during every shift for a month, said Jesse McDermont, BART’s assistant superintendent of rolling stock. 

“We got to a point where we couldn’t keep up,” McDermont said.

Xueer Lu video

Only three out of the four BART maintenance shops have the wheel lathe needed to repair the wheels, and one of those machines is 80 years old. 

The wheel lathe acts like a big sander, shaving the 33-inch wide wheels down until they are a uniform circle again. Repairing flat wheels can take from four to 16 hours — the bigger the spot, the more metal the wheel lathe has to shave.

“It was ridiculous. That machine ran 24/7,” McDermont said. He recalled that the Richmond shop’s machine was operated for so long that it overheated and had to be shut down at one point.

BART policy is to put a car in for maintenance for any wheel spot. However, according to Allison, small wheel spots are not a safety hazard for riders — more of an annoyance when the wheel defects produce the signature piercing, screeching noise. 

“It’s a comfort thing,” McDermont said. 

Catching wheel spots early means shaving off less metal so that the wheels can last longer — up to a full lifespan of 10 years. The longer a train rides on wheel spots, the worse the deformity gets, potentially damaging the track rails and leading to derailments. 

“In my experience, BART shops cars for wheel spots way sooner than anybody else,” said McDermont, who joined BART recently after working at other transit systems including Sonoma-Marin Area Rail Transit. “Someone said we had to take a car for a half-inch flat spot. I said, ‘What are you crazy?’”

From December to March, BART had retired so many trains due to wheel spots that it didn’t have enough available to meet its regular schedule. 

“We just felt that for that short period of time until we diagnosed what the issue was, we would live with the wheel flats and taking cars out of service, because we were confident that we would be able to fix it,” Allison said. “It wasn’t a long-term problem.”

But when the rain dragged on and BART mechanics were overrun with cars needing wheel spot repairs, BART temporarily altered its policy to allow cars with mild flat spots, which are less than half an inch, to continue running to mitigate the car shortage. 

The wheel problem was much worse on the Fleet of the Future trains, added in 2016, because the braking system is automatically triggered, and all of the cars are connected to it. So when the control system sent a faulty message to activate the emergency brake, wheels on several cars would get flats. In the older trains, the braking system is not interconnected, meaning that if one car’s brake is activated, other cars wouldn’t get wheel spots. 

“When you get a brand new fleet, sometimes it’s not going to work the way you expect it to.” said McDermont, adding that Sonoma-Marin Area Rail Transit also initially had problems with wheel spots on its new cars.

Last winter, BART was running more Fleet of the Future trains than ever. The combination of BART’s growing pains with the new cars and an aging control system created the perfect storm. 

“When we got the rain, we were still working a lot of the bugs out. The control system and the braking system weren’t quite in sync,” McDermont said.

New trains are more reliable

New trains need more time on the road to obtain real-world data for BART to come up with more accurate metrics. Relying solely on the manufacturer’s test data isn’t sufficient, given the Bay Area’s specific weather conditions, McDermont said. 

Even though the Fleet of the Future cars are getting more flat wheels, BART believes the new Bombardier-manufactured cars are more reliable.

The amount of time Fleet of the Future cars run between service delays, or when trains are behind schedule for 300 seconds or more, is 9,860 hours — that’s 4,731 more hours than the legacy fleet. Currently, there are 404 Fleet of the Future trains in service and 253 legacy cars. BART plans to retire the entire legacy fleet by 2025

“We’ve already made things a lot better from last year to this year by software updates and changing how things are done,” McDermont said.

The much-needed control system update will be completed in the next decade by the contractor Hitachi Rail. 

“I can promise you. McDermott said, “next rainy season it’s going to be much better — if we have any problems at all.” 

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