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Sepulveda Transit Corridor Project: How quiet is that monorail? It is not a whisper.


LA TRANSPO - In the monorail fan clubs, there is a phrase bandied about which is used as a type of touchstone on the supposed superiority of a monorail: “Whisper quiet.” 

I’ve been a transit advocate shortly after I began riding buses and trains in Los Angeles in 1993 to first reduce my personal deposits of car exhaust to the air pollution in the basin, making the Los Angeles region the perennial area in the U.S. with the dirtiest air. 

Then, with the realities of the existential threats of climate change from global warming carbon gases, I increased my personal efforts to ride transit as much as possible, and curtail driving. Vehicle exhaust is one of the greatest sources of carbon gases moving the Earth to frightening warmer and warmer temperatures. 

In transit meetings, on-line transit boards, and other places, monorail advocates would say their secret code, somewhat like the secret code of fraternal organizations: “Whisper quiet,” with the intent they had the upper hand in all matters transit. 

From riding monorails at Disneyland and Seattle, this idea of a whisper quiet train has never seemed right. While on the ground underneath those monorails I could easily hear them approaching. They were not quiet, at all. The rubber tires on the thick monorail and the noises of the train cars were easily heard. 

Many of the whisper quiet club seem to be men up in years, who confirmed their whisper quiet assumptions when close to a monorail. But, many men suffer hearing loss which would affect their experience. And if the wind was blowing away from the monorail and them, the sound would be quieter than in reality. 

According to a study by Yale University, a whisper is twenty-five decibels. 

It is difficult to find decibel readings for monorails. There are many for trains and subways, but very few for monorails, which confirm they are an outlier in mass transit. Most monorails are found in amusement parks. Those in cities are boutique transit, with other forms of mass transit following the same routes. 

The Sepulveda Transit Corridor is a very complex project, and there will not be any supporting transit, other than the workhorse Metro bus which could never carry the the number of daily passengers which the subway will be able to.  

It may be hard to find many noise level readings for monorail because of the lack of monorails in the world. 

Wikipedia lists 218 subways worldwide.  Wikipedia lists 43 monorails worldwide. Many of which are found in amusement parks (Disneyland and Disney World), zoos, or are slow moving, casual riding monorails, unsuitable for the large number of passengers to be moved at high speeds through the Sepulveda Pass. 

However, there is a decibel reading from Soundprint which list the Seattle Monorail at 65 decibels. This is not whisper quiet. 

The operating speed of the Seattle Monorail is 45mph, again, according to Wikipedia. 

The proposed Sepulveda Pass monorail, to be credible, would have to travel at higher speeds, perhaps up to 65mph and faster. And this leads to more issues about noises above a whisper. 

Monorails ride thick, single rails on rubber tires. To support the weights of the trains the tires will need high air inflation, which could create louder noises. Then there is the issue of more tire noise at higher speeds. 

From United tires library: 

Rubber Tires will sound louder due to, “Constant high speeds, Heavy load on the vehicle, Rapid speed acceleration and Hard braking. 

High-speed cornering. Due to these factors, the air in the grooves may be more compressed and get louder. At high speeds, there's more air circulating on the tread, which multiplies the regular tire noise. There's also air within the tire, which is like a large resonance chamber, so it may cause a drumming sound.

Furthermore, tires may squeal when you accelerate rapidly or maneuver at high speeds. This happens is because the tires are trying to find traction.”

Then there is the case of monorail noise remorse. Mumbai, India, hired a Chinese company to build for them a monorail.

From Asia noise news:

“The Mumbai Metropolitan Region Development Authority (MMRDA) had promised that the noise level of the monorail will be between 65 to 85 decibels (dB), but a survey conducted by an expert showed that it is over 90dB.

Exactly a year ago, PRK Murthy, chief of transport and communication, MMRDA, had said efforts were being made to further reduce the sound levels of motor. On the contrary, when noise activist Sudhir Badami checked the sound level, he was surprised to find that it was above 90dB.

The noise level inside the cars is more than 93dB. MMRDA had claimed that it will be a silent or quiet mode of transport,” said Badami.”

It must always be remembered that the Sepulveda Transit Corridor Project has two alternatives of the monorail above ground, on pillars, high in the air. Noises travel further, and louder when emitted from heights. The so-called whispers of the monorail would be screams and shouts, carrying through the neighborhoods of Sherman Oaks, Bel Air, and if the monorail goes to the Expo Line, neighborhoods of West L.A.

Subways are underground, and the noises from subway trains remain underground.

(Matthew Hetz is a Los Angeles native, a composer whose works have been performed nationally, and some can be found here.  He is the past President of the Culver City Symphony Orchestra and Marina del Rey Symphony. His dedication to transit issues is to help improve the transit riding experience for all, and to convince drivers to ride buses and trains to fight air pollution and global warming. He is an instructor at Emeritus/Santa Monica College and a regular contributor to CityWatchLA.)

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