What is Clean Diesel?

Share This Page

About Clean Diesel


Rail transportation is vital to the U.S. economy. Freight train engines rely almost exclusively on diesel and haul roughly one-third of the freight in the U.S. Commuters in cities across the country rely on America’s railroads every day. The latest diesel innovations deliver near-zero emission reductions and contribute to climate goals.

Freight train engines rely almost exclusively on diesel. The first over-the-road diesel freight engines entered service in the 1930s and the number of diesel-powered trains in the U.S. surpassed 1,000 in 1940 - most for passenger service.

According to the latest available data from the U.S. Bureau of Transportation Statistics (BTS), at the end of 2018 just over 26,000 freight locomotives were in operation in the U.S., and 431 passenger rail AMTRAK locomotives. Other state transit agencies operated regional rail services powered predominantly with diesel engines. With the exception of a few passenger rail lines that are electrified (Amtrak’s Northeast corridor and Harrisburg, PA line), the remainder of passenger rail and all of freight rail in the U.S. is diesel-powered consuming 65 million gallons of diesel fuel in 2018.

While the average car engine today has about 200 hp, locomotive engines typically start at ten times that amount. Train operators rely on diesel power across the full range of rail power applications:

Diesel engines have substantial economic advantages over other power sources for locomotives. In addition, diesel locomotives accelerate quickly and run at high speeds with minimal track damage. They function with similar efficiencies as electric locomotives, but do not require the capital investments in substations and electric distribution networks.

Regulations and Standards

The diesel industry and rail manufacturers continue to invest resources and make strides toward producing the cleanest train technology possible. Diesel engine technology in railroad locomotives has advanced dramatically in recent years. Fuel-efficiency has increased 61 percent since 1980.

In 2004, the U.S. Environmental Protection Agency (EPA) released its Final Nonroad Diesel Rule that will require train engines meet strict air quality standards. As part of this standard, trains will be required to operate using low sulfur diesel fuel that reduce sulfur emissions by 99 percent. These fuel improvements will create immediate and significant environmental and public health benefits.

At the same time, clean rail standards will also require the use of advanced emission-control technologies similar to those already in place for heavy-duty diesel trucks and buses. The availability of clean non-road diesel fuel means that advanced clean diesel emission control technology will reduce NOx and PM emissions by 90 percent from new rail engines.

Today, the transformation to near-zero emissions in locomotive engines for every application is complete, with new engines manufactured beginning in 2015 now achieving the U.S. EPA Tier 4 emissions regulations for both particulate matter and oxides of nitrogen. Replacing a single older switch locomotive with a new Tier 4 near-zero emissions diesel engine can generate the same emission reduction benefits as taking 8,000 cars off the road for a year.


Advanced Rail Technology Delivers Clean Air and Climate Benefits

While new Tier 4 near-zero emissions diesel solutions for passenger and freight rail are here, introducing them into the fleet of locomotives may take some time. Research confirms that locomotive engines are in service on average for more than 50 years. This means that there is a large population of much older engines designed before emissions standards were required still in service. Replacing these much older locomotives with new near-zero emissions diesel engines can do a lot to immediately reduce emissions in the communities where they serve.

Global locomotive manufacturer Siemens partnered with engine manufacturer, Cummins, to develop a near-zero emissions locomotive for AMTRAK’s aging fleet. Seventy-five new AMTRAK Charger locomotives are expected to enter service in 2021 powered with powerful 4,000 HP Cummins QSK90 diesel engines to reduce emissions by 90 percent and saving fuel as well. These new more efficient diesel engines are expected to reduce C02 emissions by 10 percent.

Diesel engines are capable of integrating hybrid systems and there is no reason why locomotives cannot benefit from these advances. Near-zero emissions diesel engines are coupled with energy savings and storage technology to deliver superior environmental performance. Engine manufacturer MTU developed a hybrid PowerPak system that can be customized for any rail application to deliver a 25 percent reduction in CO2 emissions alongside Tier 4 environmental benefits.

Machine learning can make big machine more efficient. ProgressRail, a division of equipment manufacturer Caterpillar, integrated advanced electronic controls into the latest locomotive designs that couple Tier 4 near-zero emission reduction benefits with fuel savings performance. If you have ever seen a locomotive in action, you may have noticed several locomotives operating in consist to move passenger or rail cars. The latest electronic innovations allow these engine to operate as efficiently as possible and eliminate idling to deliver superior fuel savings performance.

The original diesel engine patented by Rudolph Diesel over 100 years ago was designed to operate on biofuels. Today the same holds true as diesel engines old and new can operate on renewable diesel fuel and high quality blends of biodiesel to deliver significant greenhouse gas emission reductions. VirginAtlantic operating the Brightline highspeed passenger rail service in Florida is committed to using biodiesel to reduce the carbon footprint of the ride by 20 percent.  



About Clean Diesel Overview

Sign up for diesel direct

weekly analysis & commentary from the diesel technology forum