BART Makes Headway against Headache-Inducing Howl

More than half of BART's fleet now has a less wear-prone, less noise-inducing tapered wheel profile

BART wheels waiting to get with the grind. Photo: BART
BART wheels waiting to get with the grind. Photo: BART

This week BART announced that it has ground and reshaped the wheels on more than half of its train cars, as part of an ongoing effort to reduce the transit system’s infamous and ear-splitting howl. The wheels are being ground to “an advanced wheel profile that reduces both noise and wear on the rail,” wrote the railroad in its announcement about the milestone.

BART produced an informative podcast/interview with Ben Holland, a managing engineer at the agency, to discuss the science of wheel/rail grinding and noise. In the podcast, Holland explains that a “train’s wheels and the rails interact together as a system. The effort to quiet the BART system is really a partnership between our railcar department and our track department. That means the shape of the wheel and the shape of the railhead together are critical to ensuring safe and quiet operation.”

As many Streetsblog readers are aware, BART trains were originally designed with a cylindrical/flat surface wheel. Normally, train wheels are designed with a slightly tapered/conical shape, which is what keeps a train on its tracks (the flanges on the sides of the wheel are actually a backup). The idea back in the 1970s was to use cylindrical wheels to compensate for the annoying side-to-side motion that one experienced on older trains. But as train technology evolved, better ways were found to reduce that side-to-side swaying effect. Meanwhile, BART’s cylindrical wheels created their own problems. They cause excessive wear to the rails–and they helped generate a corrugated pattern on the rail surface. That pattern acts like a violin string and generates BART’s terrible howling sound.

A BART wheel getting ground into a new shape. Photo: BART
A BART wheel getting ground into a new shape. Photo: BART

By slowly grinding and replacing rails, and grinding train wheels into a more standard, conical profile, BART is slowly getting those noise levels down. “We’re actually seeing 15 to 20 Dba sound pressure level improvement and that really correlates well to the noise that we hear. Of course, people react differently to noise but overall the feedback from our customers has been very positive. They’ve noticed the improvement and our complaints have dropped dramatically as a result,” said Holland in BART’s podcast.

In other words, BART is still loud, but it’s becoming possible to have a conversation on the train without shouting.

BART expects to have nearly all its wheels reshaped in early 2019. Meanwhile, the new “fleet of the future” already comes with the quieter wheel shape.

Check out the full interview here for a lesson in BART noise and train wheel/rail dynamics.

  • Michael Escobar

    I was on a brand-new BART railcar yesterday to travel north from Warm Springs – the newest BART extension aside from the new Antioch line. The trip through the tunnel underneath the park in Fremont was still hella loud. : (

  • Roger R.

    Crap. That’s not good. Do you do that trip often? Maybe install a dB meter on your phone and take some screen shots?

  • Michael Escobar

    I generally do it twice a week. Do you have a recommendation for a good iPhone dB meter app?

  • Roger R.

    No, sorry. I had one on Android OS years ago on an old phone, but I don’t recall what it was. If you get one, maybe do an ambient test on a stopped train or in the station for comparison. I’ll be curious what it says, especially on the “fleet of the future.”

  • Affen_Theater

    Agreed, that’s not good. Since @disqus_xdYSW1ScJg:disqus said it was a new “fleet of the future” train (using a conical wheel profile), I’d guess the rail heads need to be (re)ground to ensure they have the right (and smooth, corrugation-free) profile. Although those rails should be relatively new, they’ve probably seen essentially nothing but old corrugation-inducing conical wheels since they were installed for testing up until today’s revenue service.

    I have a real digital dB (sound) meter, but live in Caltrain country and almost never ride BART, especially in the Fremont WSX area.

  • Mike

    The primary reason the wheels have a conical shape is to handle turns in the track. Both wheels are rigidly attached to the same axle, so they spin at the same rate despite having to take a slightly longer or shorter path through turns. The wheels naturally center themselves along the track until they land on a spot on their cones that provide the correct diameters relative to their different travel distance, ie the inside wheel which is traveling a shorter distance shifts to a smaller diameter point on the cone so that its distance traveled is lower than the outside wheel which is traveling a longer distance through the curve. https://gizmodo.com/the-reason-trains-have-angled-wheels-is-incredibly-clev-1793213013

  • thielges

    I use SpectrumView by Oxford Wave Research. But take any dB readings with a grain of salt because I doubt smartphone microphones are calibrated.

  • Roger R.

    Well done. But I’ve always thought nobody’s better at explaining this than good old professor Feynman. But conical wheels are also susceptible to hunting oscillation, aren’t they? Which is why trains tend to snap side to side on straightaways sometimes, no? https://youtu.be/WAwDvbIfkos

  • SuperQ

    Yes, but modern trains have dampeners on the bogies, just like the shocks on a car, to eliminate hunting oscillation.

  • neroden

    The people who originally designed BART were idiots who thought they knew everything. They were aircraft engineers who didn’t bother to learn how trains worked. It resulted in a lot of stupidities, which BART has spent decades fixing.

  • Frank Kotter

    I’ve been living off and on in Germany for the past twenty years and passenger trains have neither squealed nor oscillated since my fist months there. Do any train nerds know if their technology and wheel/track marriage profile is exceedingly more expensive or any other reason this is something the Germans have mastered but not the Americans (not just the BART, many others….)

  • maddog49

    Merritt College in Oakland has a music instructor named Fred Frith. Mr. Frith is an accomplished avant-garde guitarist. He is an expert at making art out of common everyday noises. Years ago, Mr. Frith recorded the train wheel squeal from the Tokyo subway, then recorded some jazz to go with it.

    I don’t live in the S.F. Bay Area, but when I have visited, I have ridden on BART. Ever since I found out about Mr. Frith’s song, I have thought of it upon hearing the wheel squeal.

  • LazyReader

    BART is 40 years old and needs to be dumped. NOthing short of sinking billions of dollars of additional cash past it’s current expenditures is gonna cure it’s woes. The industry
    should stop building new rail lines; replace most existing rail lines with buses as they wear out; pay down debts and unfunded obligations; and target any further subsidies to low-income people rather than continue a futile crusade to attract higher-income people out of their cars.

  • Frank Kotter
  • LazyReader

    BART was cutting edge……..in 1972. But it’s innovation led to it’s downfall.

    It’s 1,000 volt traction system unlike any other in the industry

  • crazyvag

    Many parts of BART still provide better functionality despite not being cutting edge. Many can easily be leveraged further with little ease then many other systems would dream to have.

    There’s plenty of capacity left in BART that can be tapped without total replacement as you imply.

  • Blair Mastbaum

    It’s true. U-bahn, S-Bahn, and Deutchebahn are all incredibly easy on the ears.

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