How Los Angeles Began Its Experiment With Steam-Powered Buses…Plus, Its Rare Documentary Film

Steam bus

(Click for more information)

Today marks the anniversary of an important experiment in the history of local transportation and alternative fuels.

On this date in 1972, the Southern California Rapid Transit District took delivery of a prototype steam turbine-powered bus for a year-long demonstration project.

SCRTD joined transit agencies in San Francisco, Sacramento and San Diego in testing the feasibility of using external combustion engines, the most familiar of which is the steam engine — technically known as the Rankine cycle engine.

Steam-propelled road vehicles dated back to a French tractor in the 1760s, and steam buses debuted in London in 1919 and in Detroit in the 1920s.

Here at home, the California Legislature had been addressing motor vehicle air pollution since at least 1959.

It determined in 1967-68 that state and federal agencies’ findings regarding alternatives to the traditional internal combustion engine warranted further investigation regarding application to transit.

The State Assembly decided to sponsor a demonstration project which evaluated the technical feasibility and public acceptance of external-combustion engines as low-emission alternatives to contemporary city buses.

The project was funded by UMTA, the Urban Mass Transit Association (the predecessor to the Federal Transit Association), and was the first federally-funded demonstration project related to alternative-fuel transit buses.

Los Angeles Mayor Tom Bradley

Los Angeles Mayor Tom Bradley inspects the engine bay of a steam-powered bus, August 20, 1972 (Click for more information)

In 1970, three different contractors began engineering systems for three different transit agencies in California.

William M. Brobeck & Associates of Berkeley was paired with nearby Alameda-Contra Costa Transit District (AC Transit) headquarted in Oakland, Lear Motors Corporation of Reno, NV was matched with San Francisco Municipal Railway (SF Muni), and Steam Power Systems of San Diego partnered with the Southern California Rapid Transit District in Los Angeles.

The California Assembly Office of Research provided overall direction to the three-agency project, assisted by two systems management firms.

They participated in two high profile demonstrations.

The Brobeck-AC Transit team was shown off to U.S. Department of Transportation officials, members of Congress and guests in Washington D.C.

On April 26, 1972, all three steam buses were demonstrated before members of the California Legislature in Sacramento.

A Steam Bus documentary film was recently discovered by Metro Transportation Library staff in its Archive.

It describes the project and shows footage from the project’s demonstration before Congress and transportation officials, and covers just how the standard buses were retrofitted for a lightweight steam engine system.

The Library has preserved the only known copy of this film in existence:

(Part II of the film can be found below).

Overall, the Steam Bus Project resulted in numerous findings regarding the use of Rankine cycle engines for public transit buses.

Acceleration, top speed and hill climbing were equal to or exceeded road performance of buses powered by six-cylinder diesel engines.

Tests conducted by the California Air Resources Board showed steam buses to be well below the 1975 California emission standards for heavy duty vehicles.

The California Highway Patrol reported that the quietest steam bus was 2.5 to 10 decibels below the quietest diesel buses in drive-by tests and 6 to 14 decibels below in curb-side tests, while interior sound levels were similar to or higher than diesels.

Conventional driver controls were used on the steam buses, minimizing special driver training.

And while these experimental vehicles also matched up well against diesel buses in the areas of revenue service (e.g. comfort, rider acceptance), they showed promise in their potential for further fuel consumption improvement and potential for emissions improvement.

In light of these glowing reviews regarding steam buses overall, what happened after the demonstration period was over?

Unfortunately, Los Angeles encountered more than its fair share of problems with the Steam Bus Project.

The California Steam Bus Project Final Report reports the Southern California Rapid Transit District experience as follows:

During the first week of public service, the SCRTD steam bus encountered numerous difficulties.

Its first two days of attempted public service on September 5 and 6 were aborted, because a bolt sheared on the combustor air fan assembly and a gear mechanism in the oil pump failed.

On September 7, the bus entered public service, but it completed only a one-way trip of 7.3 miles because a pulley slipped which prevented the fan from turning inside the boiler.

On September 8, the bus was withdrawn from public service when a boiler leak was detected; however, the bus traveled 86 miles on September 11 during performance testing until the boiler leak deteriorated.

After the bus was towed to San Diego and the repaired boiler was installed, the bus returned to Los Angeles on September 28 and re-entered public service on September 29, operating on Wilshire Boulevard.

It completed a successful 15-mile round trip with air conditioning operational and favorable performance, except for a loose battery terminal which caused a 27-minute delay.

The bus thereby completed its second and last day of public service because vendor and fleet operator contracts expired on September 30.

In 5.5 months since March, this bus logged 1,007 miles.

Ultimately, the Los Angeles Steam Bus from its San Diego-based manufacturer was in service for only two days, whereas the other test cities witnessed greater success.

Still, the California State Legislature’s Assembly Office of Research concluded that the Steam Bus Project successfully completed its goals.

Extensive surveys and measurements of community attitudes were conducted.

The steam propulsion systems were the first alternate power systems to be visibly supported by the public sector.

The participation of both public and private entities at an early date was viewed as very beneficial.

The Office went on to make several specific recommendations regarding the adoption of Rankine cycle engines.

It urged the exploration of an application for heavy duty vehicles in a research and development program including design engineering and bench testing rather than studies and demonstrations, including funding of at least $20 million over a four-year period.


The California Steam Bus Project Final Report contains many more details about this pivotal moment in California’s alternative-fuel transit vehicle history, as do other reports in our online full-text access document collection.

The entire project was further reviewed in detail in a paper presented at the International Automotive Engineering Congress held in Detroit in 1973.