Why Do Diesel Trains Have Electric Motors?

Switchers (or shunters), locomotives used for moving trains around in railroad yards and building and disassembling them, were the first to utilise diesel–electric technology in the 1920s. The American Locomotive Company was one of the first companies to offer “Oil-Electric” locomotives (ALCO). In 1931, the ALCO HH series of diesel–electric switchers went into production. The system was modified in the 1930s to accommodate streamliners, the fastest trains of the day. Diesel–electric powerplants were popular because they substantially simplified the transmission of motive power to the wheels, as well as being more efficient and requiring less maintenance. When a locomotive has four or more axles, direct-drive transmissions can become quite complicated. A direct-drive diesel locomotive would also necessitate an excessive number of gears to keep the engine within its powerband; connecting the diesel to a generator solves this problem. In a direct drive system, a torque converter or fluid coupling can be used to replace the gearbox. Hydraulic transmissions are said to be more efficient than diesel-electric transmissions.

Do diesel trains have electric motors?

Despite the name, diesel locomotives use electricity to propel them ahead. A huge diesel engine spins a shaft that powers a generator that generates electricity. The traction motors, which are enormous electric motors at the wheels, are powered by this electrical energy.

Why do train locomotives use electric motors?

A locomotive that is powered by electricity from overhead lines, a third rail, or on-board energy storage such as a battery or a supercapacitor is known as an electric locomotive.

Because the electric generator/motor combination solely functions as a power transmission system, locomotives with on-board fueled prime movers, such as diesel engines or gas turbines, are classified as diesel-electric or gas turbine-electric locomotives rather than electric locomotives.

Electric locomotives benefit from electric motors’ high efficiency, which is often above 90%. (not including the inefficiency of generating the electricity). Regenerative braking, which allows kinetic energy to be recovered during braking and used to put power back on the line, can improve efficiency. Regenerative braking is available on newer electric locomotives thanks to AC motor-inverter driving systems. Because there is no engine or exhaust noise and less mechanical noise, electric locomotives are quieter than diesel locomotives. Because electric locomotives do not have reciprocating parts, they are easier to operate on the track and require less maintenance. Because the capacity of the power plant is significantly greater than the capacity of any one locomotive, electric locomotives can deliver higher power outputs than diesel locomotives, as well as higher short-term surge power for rapid acceleration. Electric locomotives are suited for frequent-stop commuter rail service. Electric locomotives are employed on freight routes with a significant volume of traffic or in locations with well-developed rail networks. Even if they utilize fossil fuels, power plants are significantly cleaner than transportable sources like locomotive engines. Geothermal power, hydroelectric power, biomass, solar power, nuclear power, and wind turbines are all examples of clean or renewable energy sources. Electric locomotives are typically 20% less expensive than diesel locomotives, with maintenance expenses of 25-35 percent cheaper and operating costs of up to 50% lower.

The expensive expense of infrastructure, such as overhead lines or third rail, substations, and control systems, is the main downside of electrification. Electrification is hampered in the United States by government policy, which imposes higher property taxes on privately held train systems that are electrified. The EPA regulates locomotive and marine engine exhaust emissions in the same way that automobile and truck emissions are regulated, in order to restrict the quantity of carbon monoxide, unburned hydrocarbons, nitric oxides, and soot produced by these mobile power sources. Because train infrastructure in the United States is privately held, railroads are hesitant to engage in electrification. Railway networks, like roads, motorways, and rivers, are considered part of the national transportation infrastructure in Europe and worldwide, and are frequently subsidized by the government. Rolling stock operators are charged fees based on how much rail is used. This enables the significant investments required for technically and economically advantageous electrification in the long run.

Why are locomotives electric?

Pistons attached to an electric generator are pushed by the ignition of diesel fuel. The produced electricity powers the locomotive’s motors, which are attached to the locomotive’s wheels. The heat generated by the compression of air during the upward cycles of the stroke is used to ignite the fuel in a “diesel” internal combustion engine. This sort of engine was created by Dr. Rudolph Diesel, the creator. In 1892, it was granted a patent.

  • An electric fuel pump delivers diesel fuel to the engine, which is kept in a fuel tank. Because of its lower volatility, lower cost, and widespread availability, diesel fuel has become the favored fuel for railroad locomotives.
  • The diesel engine (A) is the locomotive’s most important component. It’s an internal combustion engine with many cylinders linked to a shared crankshaft. The tremendous compression ignites the fuel, driving the piston down. A crankshaft is turned by the piston’s action.
  • The primary generator (B), which converts the engine’s mechanical power to electrical power, is attached to the diesel engine. The electricity is subsequently distributed to traction motors (C) via various switchgear components’ circuits.
  • The output of the main generator is regulated by the excitation field current to its windings since it is always turning, regardless of whether the locomotive is moving or not.
  • The locomotive’s power output is controlled via an electrically operated throttle by the engineer. More fuel is fed into the engine’s cylinders when it is opened, increasing mechanical power production. The electrical output of the main generator grows as the excitation of the generator increases.
  • Each traction motor (C) is connected to a pair of driving wheels directly. Using electricity as the locomotive’s “transmission” is significantly more reliable than relying on a mechanical transmission and clutch. Starting a big train from a stop would quickly burn out the clutch.

What are the disadvantages of diesel-electric traction?

In essence, a diesel-electric locomotive is an electric locomotive with its own power plant. As a result, it provides some of the benefits of electrification to a railroad without the capital expenditure of the power distribution and feed-wire system. The diesel-electric locomotive, on the other hand, has a significant disadvantage over an electric locomotive: its output is virtually restricted to that of its diesel engine, hence it can produce fewer horsepower per locomotive unit. Diesel is less suitable than electric for high-speed passenger services and very rapid freight operations because significant horsepower is necessary for high-speed operation.

Why do diesels last longer?

A gas engine would have reached the end of its life 20 years ago at about 100,000 miles, but today’s engines are constantly making another trip around the odometer. However, while gasoline engines can now reach 200,000 miles and beyond, diesel engines can also reach 500,000 miles and beyond. The following are three reasons why diesel engines survive longer than gasoline engines:


We’ve all learned the hard way that larger isn’t necessarily better. Diesel engines, on the other hand, are designed to endure longer than their gasoline equivalents. Compression ratios and cylinder pressures are higher in diesel engines than in gasoline engines. Diesel engines are designed with these factors in mind. Their crankshaft and camshaft are larger, necessitating larger bearings and stronger main and rod bolts. Increased clearance from larger crankshafts and camshafts provides for greater oil flow. Better engine lubrication means reduced engine wear, which extends the engine’s life.

Other significant design features of the diesel engine contribute to its durability, including:

  • Most diesel engines feature a gear-driven construction, which means you won’t have to worry about timing belt issues. This also saves money on costly maintenance because the timing belt does not need to be replaced.
  • Piston cooling jet – Piston cooling jets spray engine oil on the bottom of your pistons in diesel engines. This engine oil spray protects pistons from premature wear by keeping them properly lubricated, which lowers friction and keeps them cool.
  • There are no spark plugs in diesel engines, so the gasoline burns more slowly. Because of the slower burn, there is less stress and more torque, which is essential for diesel engine efficiency.

Diesel Fuel

The fuel that diesel engines burn is another reason they survive longer than gasoline engines. Diesel fuel is a form of distillate fuel made primarily from crude oil, which allows diesel engines to wear their cylinders out more slowly than gasoline engines. This adds diesel fuel lubricating qualities, extending the engine’s total lifespan. On the contrary, gasoline is mostly composed of aromatic hydrocarbons, which function similarly to harsh and corrosive solvents. This lack of lubricity causes your engine’s components to wear out prematurely. Diesel engines have lower exhaust gas temperatures (EGTs), which contributes to their increased lifetime. Despite the fact that diesel fuel has 139,000 British thermal units (BTUs) compared to 115,000 BTUs for gasoline, the principles of thermodynamics dictate that the higher compression ratio diesel engine’s expansion rate actually cools the exhaust gases faster. The first flame front is cooler due to the lower auto-ignition temperature of roughly 410°F for diesel fuel compared to 495°F for gasoline. Diesel engines also have a substantially lower air-to-fuel ratio, ranging from 25:1 to 70:1, compared to 12:1 to 16:1 for gasoline engines. EGTs are cooled by a lower air-to-fuel ratio. In addition, gasoline burns more faster than diesel fuel. Because of the slower laminar speed of the flame during combustion in diesel engines, there is less shock to the rotating assembly, which adds to their durability.

Lower RPMs

The third factor that determines how long a diesel engine lasts is its operating efficiency. In comparison to a gas engine, diesel engines have lower revolutions per minute (RPMs) and produce more torque. The ability to create the same power at lower revolutions implies less wear on your pistons, rings, cylinder walls, bearings, valves, and guides, extending the life of your engine. When diesel engines are not in use for long periods of time, they are usually left running. The regular cycling of turning the engine on and off saves wear compared to a gasoline engine since a major percentage of wear occurs at starting. It also decreases heat cycles and maintains stable operational temperatures.

Expert Spotlight:

PSP Diesel in South Houston, TX, is known for their 6.0L Ford Powerstroke builds, and Stephen Peters has this to say about why diesel engines survive longer:

“Diesel users often use their engines for far more than what they were designed for. In contrast to the conventional start/stop patterns of a gasoline engine, this is typically done to generate maximum torque and run for longer periods of time during the day. They aren’t exposed to abrupt starts and stops. One of the most abrasive actions on a motor is starting it. While idling your engine is not good for its longevity, that is exactly what the majority of these trucks are doing. They run long hours and are worked very hard because they are started at the beginning of the day and shut off at the end, but that is their job.”

Peters continues, “Diesel engines are simply intended to be more durable. For example, the blocks are larger, the walls are thicker, and the pistons are larger. And, even with the extra weight, let alone the tight tolerances in the rings to avoid blow-by, the design was created with lubrication in mind, reducing friction and damage to the rubbing parts.”

How much electricity does a diesel locomotive produce?

The hybrid diesel locomotive is a marvel of engineering and power. It blends cutting-edge mechanical technology, such as a massive 12-cylinder two-stroke diesel engine, with heavy-duty electric motors and generators, as well as a dash of computer technology.

This 270,000-pound (122,470-kg) locomotive is capable of towing passenger-train cars at speeds of up to 110 mph (177 kph). The diesel engine produces 3,200 horsepower, which may be converted into about 4,700 amps of electrical current by the generator. Over 64,000 pounds of torque is generated by the four drive motors using this electricity. The rest of the train is powered by a V-12 engine and generator that is completely independent from the rest of the railway. The head-end power unit is the name for this generator. The one on this train has a power output of over 560 kilowatts (kW).

Are electric trains better than diesel?

A group of progressive activists and railroad business specialists has proposed that the federal and state governments, in collaboration with the railroad industry, participate in a long-term initiative to electrify US railroads. They detail a plan to update freight and passenger railways with overhead wires to carry high-voltage electricity generated in towns along the lines, and replace diesel locomotives with electric engines in a book published in October 2016, Solutionary Rail, a people-powered campaign to electrify America’s railroads to a clean energy future. These cables would also help supply electricity generated by distributed renewable energy sources by creating a new, nationwide electrical transmission system. The book lists various advantages of an electrified railway system over the current system in the United States, but industry and government analysts are pessimistic that the proposal will be implemented.

One thing that all analysts agree on is that long-haul transportation by train is more efficient than by truck. Steel rolling on steel is far more efficient in terms of energy transfer than rubber rolling on concrete, creating just approximately one-fifth of the friction. Trains are also more aerodynamically efficient than lorries. Overall, railways transport freight 1.9 to 5.5 times more effectively than trucks, with substantially lower overall labor costs and far less pollution. Truckers could also benefit from a change to rail for long-haul freight because they could focus on the last miles of the voyage and work more normal hours. A cleaner, more robust railroad system may replace a significant percentage of truck traffic, while also improving the reliability and competitiveness of intercity passenger service compared to highways and airlines.

Electric Trains vs. Diesel Trains

Trains are more efficient than trucks, but not all trains are created equal. Diesel trains send roughly 30% to 35% of the energy generated by combustion to the wheels, whereas delivering electricity straight from an overhead powerline delivers about 95% of the energy to the wheels. According to the authors of Solutionary Rail: Electric Trains, there are several further advantages of using electricity rather than diesel to power trains.

  • While diesel fuel prices are now low, many analysts believe that the long-term trend will be for them to rise. Electricity prices, on the other hand, are lowering as the usage of renewable energy sources expands. Even at present pricing, using the energy conversion rates mentioned above, it is predicted that running a train on electricity is 50% less expensive than running one on fuel.
  • On the global market, electric locomotive engines cost around 20% less than diesel locomotive engines, and maintenance expenses are 25-35 percent lower than diesel engines.
  • Diesel locomotives would be phased out, reducing air pollution such as soot, volatile organic compounds, nitrogen oxides, and sulfur oxides, all of which are harmful to human health and the environment. This is particularly essential because many railroads run through cities. It would help minimize city noise levels and highway fatalities caused by trucks (rail freight causes only about one-eighth as many fatalities as truck freight per ton-mile).
  • Switching from diesel to electricity would also help with the problem of replacing petroleum-based liquid transportation fuels with greener alternatives as part of our efforts to reduce greenhouse gas emissions.

Solutionary Rail not only asks for the electrification of railroads, but also for the use of renewable energy sources to power the new electric railroad system. Renewable energy sources might be connected across the country if transmission lines are installed with enough capacity, producing a nationwide electric power grid that also supplies all of our railway energy demands. Railway electrification would not only provide a new market for renewable energy, but it would also offer it access to a variety of other sectors. The variable production of electricity by wind turbines and photovoltaic solar panels would be offset by the large range of sources (the country isn’t always gloomy or windless).

Why Didn’t U.S. Railroads Go Electric?

Why aren’t electric locomotives more widely used in the United States since they have so many advantages over diesel locomotives? During much of the twentieth century, railroads in the United States were the world leaders in innovation and the use of cutting-edge technology. They have now fallen behind many other sophisticated nations, which have been investing in electric-powered trains for many years. Steam locomotives were replaced by more efficient electric locomotives and diesel-electric (often referred to as just diesel) locomotives in the early to mid-twentieth century. During that shift, railroad firms in the United States preferred diesel locomotives over electric locomotives because diesel has lower upfront costs, even though electric systems are less expensive to operate and maintain. Electric locomotives were chosen by railroad operators in many other developed countries, partially because the railroads were owned by the governments of those countries, who could better finance the necessary transmission infrastructure. Because railroads in the United States have historically been a regulated private sector industry, financing electrification upgrades is far more difficult than building diesel-fueled systems. As a result, electrified rail is currently used on less than 1% of railroad tracks in the United States, despite the fact that electricity provides more than one-third of the energy used to power trains worldwide.

In the United States, a few passenger rail lines (Amtrak’s Northeast corridor and the Harrisburg, PA, line) have been converted to electric power, while the rest of passenger rail and all freight train is diesel-powered. CalTrain, California’s commuter train system, is being upgraded to very high speed rail (VHSR) service, which will run on electricity. The system is expected to be operational by 2022 at a cost of $5 billion at the outset. Other electric VHSR systems (which would be powered by electricity) are being studied around the country, although money has not yet been secured.

Is Rail Electrification a Feasible Undertaking in the United States?

Transitioning from the current railway infrastructure in the United States to a nationally electrified rail system is a major endeavor, and the Solutionary Rail proposal does not include a cost estimate. It does, however, note that many other countries (Switzerland, Sweden, the Netherlands, Italy, France, Germany, Russia, China, India, Japan, and so on) have made substantial attempts to electrify their railway networks, and that many more are currently doing so. However, because their railway services are government-owned and run, whereas U.S. railways are privately held, it is easier for other countries to acquire finance for big infrastructure expenditures like this than it is for their American equivalents (except for Amtrak, which is partially government-funded).

If there was ever a political reason, the US government could mandate that all railways be electrified by a specified date. The massive investment required is an apparent roadblock, and there is little appetite in Congress to reduce the nation’s carbon impact by converting to electric rail. Our would be more difficult in this country than in Europe or Asia, where urban populations are denser. While several other technologically advanced countries (e.g., Japan, Germany, France, Mexico, and Australia) have seen steady decreases in their consumption of petroleum (from which diesel is derived) in recent years, the United States’ consumption of petroleum has increased, owing in large part to transportation demand. I Despite the fact that the transportation sector emits 27% of all greenhouse gases in the United States, there is no national discussion about limiting the usage of combustion engines. ii

Public-Private Partnerships, Industry and Labor Groups Could Make the Difference

Some suggest employing a combination of federal, state, private sector, and possibly regional money to construct an electrified rail network through public-private partnerships (PPPs). In recent years, PPPs have been successful in a number of railroad projects, including the Norfolk Southern Heartland Corridor, which connected the Ohio-West Virginia-Virginia lines (and commenced service in 2010), and the Alameda Corridor, which connects Long Beach and Los Angeles, CA (which began operation in 2002). Electrification of freight train might begin with a demonstration project along the Northern Corridor, which connects various cities and villages from Seattle to Chicago. Several funding models to involve public and private actors in the investment process have been presented.

A push to electrify might garner the help of a variety of industrial and labor groups. Railway electrification would create new opportunities for rail employees (as well as many other industrial trades), making it appealing to labor unions, which might assist win public support for electrifying and modernizing railroads. Several railroad unions are likewise in favor of a more sustainable economy and would certainly support railway electrification. Railroad Workers United, for example, has approved a resolution to move the railroad industry away from fossil fuel shipping and toward more sustainable business prospects. Railroad Workers United represents rail workers from a number of unions involved in North American rail transport. The agriculture sector may be interested in railway electrification as a cost-effective means of moving produce. Agricultural items make up a far smaller percentage of freight rail shipments than fossil fuel shipments, and hence take a back seat in rail traffic. Rail shipments might become considerably more punctual and frequent than they are now, thanks to the greater capacity that electrified railways could give. Electric utilities may also play a role in assisting railway electrification. Utilities are one of freight rail’s most important customers, especially for delivering coal to power plants and carrying coal ash away. The revenues of freight train will decline as utilities become less reliant on coal, unless the railways establish a new business model, such as one that includes energy transfer. Finally, Native American tribes may gain from the project if their right-of-ways are properly negotiated and compensated, as well as if they are allowed to use the new transmission routes to distribute the electricity they create.

The fact that no federal, state, or municipal government action has been taken since the publication of Solutionary Rail in 2016 does not bode well. One critic challenged the idea to electrify railroads shortly after it was published, citing a number of economic issues. The critic, on the other hand, overlooked the environmental benefits of converting to electric-powered rail. Prioritizing the reduction of fossil fuel consumption, including the transition away from diesel fuel, is vital to avert the worst effects of climate change. Although such a transformation will be costly and time demanding, it is nonetheless necessary.

According to the US Energy Information Administration, petroleum consumption in the United States increased by 3.06 percent from 2013 to 2015. https://www.eia.gov/todayinenergy/detail.php?id=30652

ii. Environmental Protection Agency, Sources of Greenhouse Gas Emissions, September 26, 2017, https://www.epa.gov/greenvehicles/fast-facts-transportation-greenhouse-gas-emissions.

How far can a train go on a gallon of diesel?

The formula for our 2018 fuel economy rating is as follows: (Source: CSX R-1 Report 2018)

  • Lines 1+3 (Line 4) of Schedule 750, Diesel Fuel Consumption (Freight + Switching) = 423,998,863 gallons

Over the previous decade, CSX has spent more than $2.8 billion on improving locomotive fuel efficiency and lowering emissions.

The ton-mile-per-gallon is a unit of measurement used to compare the effectiveness of various types of transportation while moving freight.

The rail business keeps track of revenue ton-miles and publishes them “Surface Transportation Board Annual Report” (commonly referred to as the R1 Report). ‘The’ “The annual value of “Ton-Miles of Freight” is recorded in Schedule 755, line 110 of the R1 Report. In the R1 Report, Schedule 750, line 4, the rail sector also tracks and reports annual fuel usage. The system-wide train efficiency value is calculated using these two stated values.

For example, CSX recorded 208,712,027,000 ton-miles of freight in the R1 Report in 2018, and the combined line haul and switcher reported fuel usage was 423,998,863 gallons.

In other words, based on our 2018 revenue ton miles and fuel use, CSX trains can move a ton of freight nearly 500 miles on a gallon of fuel.

A freight truck’s fuel economy can be calculated in a similar method. For example, assuming an average 7 miles per gallon truck fuel efficiency and a typical truck payload of 19 tons, a heavy-duty diesel truck moving 19 tons of freight over 500 miles would burn approximately 71 gallons of diesel fuel. This freight haul’s efficiency would be computed as follows:

This efficiency could be described as follows: “On a gallon of gas, a truck can transport a ton of freight 134 miles.”

Similarly, a normal train might transport 3,000 tons of freight for 500 miles while using 3,049 gallons of diesel fuel. This freight haul’s efficiency would be computed as follows:

This efficiency could be described as follows: “On a gallon of fuel, a train can transport a ton of freight 492 miles.”

As illustrated by the ratio of 492 train ton-miles per gallon split by 134 truck ton-miles per gallon in this example, the train is nearly 3.7 times more efficient at moving freight.