Study Shows Dramatic Drop In Pollution Following Switch To Electric Trains

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Over a six week period in the fall of 2024, Caltrain, which operates commuter rail service between San Francisco and San Jose, California, replaced all its diesel-powered self-contained trains and locomotives with electric equipment. The fact that this transition happened so quickly gave researchers a rare opportunity to measure the difference in air quality in and around the main San Francisco train terminal before and after the equipment changeover.

In particular, they were interested in measuring the amount of black carbon — what some might call soot — in the air before and after the switch. The results of that study were published in the journal Environmental Science and Technology Letters. Measurements were taken at three locations in and around the train station. The researchers said:

Caltrain’s San Francisco station is in a busy commercial and residential neighborhood typified by 3–18 story buildings. The station is a stub-ended design with 12 main tracks located to the southwest of an enclosed ∼1600 square meter station building and to the north of a 6.5 hectare rail yard. Prevailing westerly winds cause the passenger platforms and station building to be consistently downwind of locomotive emissions. We established three measurement sites in the vicinity of the SF station:

• Upwind site in an unused observation tower overlooking the rail yard. This site’s sampling inlet (8 meters above ground) was approximately 150 meters upwind of the parking location of most diesel locomotives. Nearby emissions sources include an on/off-ramp of Interstate 280 (∼200 to 250 meters  upwind), and arterial streets in the neighborhood.
• Platform site located outdoors at the NW end of passenger platforms, with sampling inlet placed approximately 25 cm above ground level and ∼150 m from the exhaust stacks of diesel locomotives.
• Station concourse site inside the station building, with the sampling inlets located 1.5 m above ground level, and ∼8 m from the platform doorways.

In addition, measurements were taken within the passenger cars themselves. On the journey from Sam Francisco to San Jose, the locomotive was in front, which meant its exhaust passed directly over the passenger cars and the vents that provide ambient air to the passengers inside. On the trip north, the locomotive was in the rear of the train, which meant fewer black carbon pollutants reached the interior of the cars.

Electric Trains Slash Emissions

The results of the study, as reported by Science Direct, were not surprising, but notable nonetheless. Switching from diesel to electric trains reduced passengers’ exposure to the carcinogen black carbon by an average of 89%. It also significantly reduced the ambient black carbon concentrations within and around the San Francisco train station.

“The transition from diesel to electric trains occurred over just a few weeks, and yet we saw the same drop in black carbon concentrations in the station as California cities achieved from 30 years of clean air regulations,” said study senior author Joshua Apte, a professor of environmental engineering and environmental health at the University of California, Berkeley. “It really adds to the case for electrifying the many other rail systems in the U.S. that still use old, poorly regulated diesel locomotives.”

Apte, an expert in air quality monitoring, was inspired to pursue the study after visiting a Caltrain station in August 2024, when the very first electric trains were being introduced. “I was stunned at how much the station smelled like diesel smoke and how noisy it was from the racket of diesel locomotives idling away at the platforms, dumping smoke out into the community. A light bulb went off my head and I realized this would all be going away in a few weeks.”

After securing the support of CalTrain, Apte and study lead author Samuel Cliff began installing black carbon detectors at Caltrain stations and carrying portable air quality detectors aboard the trains. For four weeks, they tracked the rapid improvements in air quality as old diesel locomotives were replaced by new electric trains. “A lot of these transitions happen pretty slowly. This one happened in a blink of an eye,” Apte said. “We had the unique opportunity to capture the ancillary public health benefits.”

According to Apte and Cliff’s calculations, the reduction in black carbon exposure achieved from Caltrain’s electrification cut excess cancer deaths by 51 per 1 million people for riders and 330 per 1 million people for train conductors. For reference, Environmental Protection Agency policy says any exposure that increases the average individual’s cancer risk by more than one per million is considered unacceptable. “If you think about this in the context of the whole of the U.S., where we have millions of people commuting by rail every day, that’s hundreds of cases of cancer that could be prevented each year,” said Cliff, a postdoctoral scholar at UC Berkeley.

Time To Take Action

The majority of U.S. commuter trains are still powered by diesel fuel, despite the fact that electric trains are quieter, more reliable, and produce fewer greenhouse gases than diesel locomotives. Apte thinks the study should motivate more U.S. municipalities to follow the lead of Asian and European countries in electrifying their railways. “This is something that we ought to find a way to do as quickly as possible, everywhere. California has long term plans to electrify most of its rail systems, but this shows that we shouldn’t be waiting another 25 years to get it done. We should be speeding it up.”

Indeed we should be. We reported recently that China plans to build nearly 30,000 miles of high speed rail in the next 5 years. But conservatives in the US, who were all forced to read Ayn Rand novels as children, are having none of it. For more than a decade, there has been a plan to build a high speed rail link between Dallas and Houston. Last year, the Biden administration put its shoulder to the wheel to move the process forward by providing $64 million in seed money.

Public Funding For Some

Last week, the current administration took the money back. Transportation Secretary Sean Duffy celebrated the policy reversal as he sneered, “I am pleased to announce that FRA and Amtrak are in agreement that underwriting this project is a waste of taxpayer funds and a distraction from Amtrak’s core mission of improving its existing subpar services. The Texas Central Railway project was proposed as a private venture. If the private sector believes this project is feasible, they should carry the pre-construction work forward rather than relying on Amtrak and the American taxpayer to bail them out. My department will continue to look for every opportunity to save federal dollars and prioritize efficiencies.”

Once again, the U.S. has chosen to put itself behind in the race to develop new technologies, whether it is batteries and battery materials, solar panels, rare earth materials, wind turbines, or electric cars and trucks. Duffy no doubt thinks the Interstate Highway System was an expensive boondoggle, because everything government does is wasteful and prevents private industry from generating profits. Oh, the horror!

Oddly enough, the one place the current administration is willing to subsidize rail systems is on the moon. According to Fast Company, defense contractor Northup Grumman said recently it has been tapped by the Defense Advanced Research Projects Agency to develop a concept for a lunar railroad. The railroad would transport people and cargo across the moon’s surface to support the growth of a commercial opportunity on the moon.

So, for commercial ventures that want to establish an industrial base on the moon, the vault doors of the federal treasury are wide open, but for us Earthlings, the message is, “No high speed rail for you!” Welcome to life in the USSR.