“Metro Diesels Don’t Cause Smog”: The 1954 Tests “Proving” L.A. Buses Were Clean & Actually “Helped” Solve The Smog Problem

Metropolitan Coach Lines buses at Long Beach's Fairbanks Yard, 1956.

Earlier this year, Metro retired its last diesel bus from its fleet of over 2,2000 vehicles.

At that time, we took a closer look at the early history of diesel buses in Los Angeles and how Los Angeles Motor Coach‘s 1940 fleet expansion coincided with the 1943 “Birth of Smog.”

But by the early 1950s, scientists began looking into automobile exhaust as a source for air pollution.

We recently discovered an item in our Archive whose title alone is worthy of a double, if not triple-take: “Metro Diesels Don’t Cause Smog.”

In the April, 1954 issue of Metro Coach News, the employee newsmagazine of Metropolitan Coach Lines, the article highlights the findings of tests conducted by two independent engineering laboratories: The Smith-Emergy Company of Los Angeles and the Consolidated Engineering Corporation of Pasadena.

The test results conclusively show that the GMC diesel exhaust was both free from air pollutants which cause smog as well as carbon monoxide.

While only one-page long, the article contains other eye-opening facts.

Diesel exhaust testing apparatus, 1954

The decision to make the diesel exhaust tests was made during the course of public hearings before the Los Angeles Board of Public Utilities and Transportation on Metro’s proposals to replace streetcars on Hollywood Boulevard and the Glendale-Burbank Line with an all-motor coach service.

The exhaust collection process is delineated in detail.  Tests on diesel engines would be conducted using exhaust fumes from various engines collected in bottles.  The testing apparatus is explained, as is the exhaust sampling from vehicles that had been at constant speed, idling, accelerating and decelerating.

The test procedures were set up with assistance from Metropolitan Coach Lines’ General Attorney, who was also a civil engineer.  He was assisted by a number of chemists, consultants and faculty members from prestigious institutions.

The Smith-Emergy report documents the data collected during testing, but doesn’t draw any conlcusions.

However, the Metro Coach News article proudly proclaims that the diesel engines are not only free of air pollutants and carbon monoxide, but that:

Diesel coaches actually help solve the smog problem, since each motor coach replaces about 40 gasoline automobiles, which are considered to be among the primary offenders.

Rose Parade attendees line up for Metropolitan Coach Lines service to Pasadena, January 1, 1954.

The article implies that while cars had contributed to Los Angeles’ ongoing smog problem for over a decade, its diesel-powered buses had no role in air pollution.

We don’t know much about these testing procedures or ways in which they were conducted beyond what we read here, but we do know that in 1998, the California Air Resources Board (ARB) identified diesel exhaust particulate matter as a toxic air contaminant based on its potential to “cause cancer, premature death, and other health problems.”

In 2000, The Board adopted a Fleet Rule For Transit Agencies and more stringent exhaust emission standards for new Urban Bus engines and vehicles.

The Board also administers numerous diesel-related programs and activities, and sponsors health-related research in light of their attribution of about 3,500 premature deaths and thousands of hospital visits and asthma attacks in California each year to diesel particulates.

For more information, check out the California Air Resources Board’s in-depth timeline online titled Key Events In The History Of Air Quality In California.