Trains in the United States are big polluters. To start, almost all rail in this country still runs on diesel. This is a big deal because diesel exhaust wreaks havoc on our human health: it is a known human carcinogen and toxic air contaminant. Inhaling diesel particles can lead to asthma, chronic obstructive pulmonary disorder, cardiovascular issues, lowered lung function, impacts to reproductive health, and the harrowing list goes on and on.

Our state air regulator tasked with protecting our lungs and cleaning our air — the California Air Resources Board (CARB) — estimates that train pollution makes up about 15% of health-harming nitrogen oxide, or NOx, pollution from freight sources in California. In fact, starting in 2023, it is dirtier to move goods by rail than by trucks in California. This is one of the key reasons why CARB is focusing its latest efforts on eliminating locomotive pollution in our state.

Later this week, on April 27, CARB will vote on whether to adopt its In-Use Locomotive rule, a nation-leading standard that would bring all railroads operating in California to zero-emissions. This innovative rule will require all freight, industrial, and passenger railroads operating in California to clean up their fleets over time, resulting in $32 billion in health benefits and preventing more than 3,200 premature deaths. At the height of the rule’s implementation, it will prevent 63 tons per day of NOx emissions, making it the single largest emissions reduction effort in California’s plan to meet clean air standards.

It will be a truly historic moment in the fight for public health and clean air if the Board adopts this rule.

Community voices are at the center of why CARB is voting on this life-saving rule this week. There are few places where this dirty diesel locomotive pollution is more saturated than in communities located near railyards. Southern California’s Inland Empire and Los Angeles regions are all too familiar with locomotive pollution. Not only do these areas suffer from some of the worst air quality in the country, but of the 18 major railyards in California, at least 10 are situated in this region.

These facilities can reach up to several miles long and are filled to the brim with diesel locomotives, double-decker rail cars, heavy-duty big-rigs, cargo handling equipment, and other heavy-duty machinery. It’s not uncommon for railyards to operate at all hours of the day and night, blaring horns and churning diesel exhaust directly into people’s homes.

To make matters worse, many of these railyards border people’s homes. For example, Union Pacific’s Colton Railyard, which measures 5.5 miles in length, is just 350 feet from the nearest residences and neighbors a local high school. At the time of CARB’s 2008 Health Risk Assessment for the site, the UP Colton Railyard accounted for a roughly 35% increase in cancer risk for those most highly exposed.

All the while, the railroads have successfully pushed back on efforts to being regulated for years. It’s been 15 years since the U.S. Environmental Protection Agency (EPA) adopted the most stringent Tier 4 locomotive emission standards, and even today, less than 5% of trains that operate in California meet this Tier 4 standard. This is because under the federal standards there is a loophole that allows locomotives to operate indefinitely under the same emissions tier as when they were first manufactured. In practice, this means it’s not uncommon to have 60- or 70-year-old locomotives lawfully polluting just as much today as they could back in the 1950s and ‘60s.

The largest freight railroads, like Burlington Northern Santa Fe (BNSF) and Union Pacific (UP) have evaded regulation by pointing to rail as a cleaner mode of goods transport than trucks. But as trucks have gotten cleaner — thanks to California’s nation-leading zero-emissions standards, rapid technology advancements, and positive total cost of ownership for electric models — trains remain stuck in the past.

But the thing is, we have the technology today to require all rail in the United States use electric, zero-emission technology. In fact, about one-quarter of the world’s rail lines are already electrified. Locomotives powered by electricity via an overhead power line are the most established and widely used locomotives around the world. They have the most power and are capable of carrying the heaviest loads. From China, France, Russia, and South Africa to Switzerland, Ethiopia, Japan, and South Korea, much of the world operates electric freight rail systems. It’s time the United States caught up.

To top this up, important advances in battery-electric locomotive technology, rapidly declining costs of batteries, and increasing availability of fast charging show that battery-electric locomotive models are ready for the transition to zero-emissions. Lead researchers have even concluded that battery-electric freight trains can achieve cost parity with diesel today.

Thankfully, CARB seems ready to take bold action to address the diesel pollution crisis that has been bearing on Californians for far too long. The Locomotive Rule would set California on an ambitious, but achievable path to reducing pollution from railyards.

Locomotive operators have three options for compliance under the proposal. The first pathway requires that railroads invest in their zero-emissions future and retire the oldest locomotives still in operation in the State. Operators will have to deposit funds into an account every year depending on the emissions from their locomotives. Before 2030, these funds may be invested in zero-emission locomotives and infrastructure or technology that meets EPA’s most stringent Tier 4 standard. After 2030, locomotive operators can only use funds for zero-emission locomotives or infrastructure. Likewise, beginning in 2030, locomotives that are 23 years or older must be retired from use in California.

Railroads remain compliant under the second pathway if they can achieve the same emissions reductions as they would by adhering to the first compliance option.

Finally, a third pathway was added in response to concerns from passenger rail and applies to any rail operator. This option sets emission reduction milestones that become more and more stringent over five-year increments. Beginning in 2030, half of a railroad’s annual fleet usage must come from Tier 4 or zero-emission locomotives; in 2035 this grows to 100%. In 2042, half of the railroad’s fleet usage must be from zero-emissions, and by 2047, the full locomotive fleet must be zero-emissions. Since many passenger rail operators in the State have already adopted Tier 4 technology, this option offers them additional flexibility to complete the transition to zero-emissions.

CARB has a big day ahead. The Board has an opportunity to shape how one of the most polluting industries impacts the health of Californians and the very air we breathe. Now is the time to begin reaping the benefits of years-long hard work and advocacy for a cleaner future for rail. The train is leaving the station — and it better be electric.