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Rail Makes Transportation Cleaner

Rail travel is cleaner than driving or flying, but will Americans buy in?

Trains move freight at a much lower cost than trucks. The U.S. freight rail system is the best in the world, but in many parts of the country passenger rail lags behind a European model. [Image credit: Patrick Dirden / CC BY-NC-ND / Flickr]

Transportation represents a large portion — about 29%  — of U.S. greenhouse gas emissions, and the share has been rising in recent years. Rail proponents often argue that investment in trains and public transportation is a key part of making transportation cleaner, and indeed, the Green New Deal calls for greatly expanding high-speed rail.

I’m a scholar of rail, and it’s clear to me that the quickest way to decrease greenhouse gases from transportation is to travel by train and move goods by rail instead of on the road or by air.

To explain why, it’s worth comparing rail to other modes of transportation on energy consumption and emissions, and to look at some of the developments that can make rail more widely used in the U.S. and less reliant on fossil fuels.

Energy and emissions profiles

Transportation by rail is a major part of the transportation system in most countries, including in the U.S., which has the longest freight railway system in the world with approximately 140,000 miles. Rail passenger services are essential in many areas, primarily in population centers such as New York and Chicago, and intercity rail has a significant market share in some corridors, such as the Northeast. Rail also offers long-distance routes connecting many smaller communities with each other and the large metropolitan areas in the country.

Data show that rail has a significantly lower energy footprint than trucks and passenger cars. Rail transport, with hard steel wheels on steel rail, has lower resistance to motion than road transportation. And the convoy formation of individual rail cars into trains also adds to its better energy and environmental performance.

A common measure for transportation capacity is ton-miles for freight and passenger-miles for passengers to indicate that a ton of freight is moved for one mile and for passenger systems that a passenger is moved for one mile.

Freight rail accounts for about one-third of the ton-miles and consumes only about 2% of the transportation energy in the U.S. The higher efficiency can be illustrated this way: On average, freight railroads move a ton of cargo for around 479 miles on a gallon of fuel, which is about 11 times more energy-efficient than trucks on a ton-mile basis.

Passenger rail is around three times more efficient than a car on a passenger-mile basis at current occupancy levels. The lower energy consumption leads to lower greenhouse emissions.

How U.S. and European rail differ

Often there is the perception that the U.S. lags behind other countries when it comes to rail, but in many cases that is not true. The country has, arguably, the best freight rail system in the world, which is owned, operated, and financed by private companies. Passenger service in specific corridors — for example, in the Northeast — is comparable with the European counterparts. On long-distance routes and in less densely populated areas, however, there are often empty seats on Amtrak trains.

The primary difference between Europe and North America could be summarized like this: In America there is a freight rail system with some passengers, while in Europe there is a passenger rail system with some freight. The emphasis is different.

A further difference is that the rail network is private in the U.S. and operated to yield a profit, while in most other countries the rail infrastructure is owned by the government (similar to the freeway system in the U.S.) and heavily subsidized.

To compete with air for passenger transportation

Running passenger and freight trains on the same lines is possible but poses many challenges, as the characteristics of the two train types are very different; freight trains tend to be long, heavy, and comparatively slow, while passenger trains are short, fast, and comparatively light. If there are not too many trains on a line, this mixed traffic can be managed, but if there are a lot of trains, then separate infrastructure is the way forward.

When journey times are less than four hours, people usually prefer to travel by train instead of alternative options, such as air or road. For many corridors in the U.S. it would be necessary to upgrade existing lines or to build new infrastructure to achieve competitive journey times.

For the high-speed rail projects in California, which the state recently decided to scale back, and Texas, where trains would be able to travel at speeds of 200 miles per hour or more, those states are building new infrastructure. Higher-speed options often allow existing rail tracks to be upgraded to accommodate speeds of around 110 miles per hour to around 125 miles per hour, and such projects are being implemented in Florida and the Midwest.

Routes to better environmental performance

The majority of trains in the U.S. are diesel-electric, where a diesel engine runs a generator, supplying electric traction motors that turn the wheels. However, electricity can also be supplied by the grid to trains via wayside infrastructure, and this option accounts for about 4.5% of rail energy, more than for any other mode, with the majority being used in transit and commuter operation, and some intercity rail. Therefore, when the electricity generation mix becomes less greenhouse gas-intensive, those rail systems automatically follow.

For the lines where wayside electrification is not economically feasible — imagine routes that are long, such as Chicago to Los Angeles — or where traffic is relatively low, rail will continue to rely on on-board electric power generation.

Rail is developing options to reduce emissions for lines without wayside electrification too, with advanced diesel engine technologies, and exploration of less polluting energy options, including natural gas. Florida East Coast Railway has converted the majority of their locomotives to liquefied natural gas.

Having batteries to supply power to trains can significantly reduce or fully avoid conventional wayside electrification, decreasing cost and visual impact as no overhead wires are necessary on the right-of-way. These are suitable for relatively short distances and where power demand is low, such as light rail and streetcars. Detroit’s QLine, for example, operates 60 percent on battery power, or “off-wire.”

Hydrogen fuel cell applications to rail, often referred to as hydrail, enable long range with a lower environmental footprint than diesel, and such trains for regional passenger service are already in operation in Germany. In the U.S., the technology is being investigated by some passenger and transit railways, including in North Carolina, and its use for freight rail is being explored as well.

Even without these advances, rail is already more environmentally friendly than road or air. Dramatically expanding rail use, particularly passenger service, will require government investment in more frequent service on existing lines, starting service to areas that don’t have access to rail currently, reducing journey times, and building out a larger passenger rail network.The Conversation


Andreas Hoffrichter, is executive director of the Center for Railway Research and Education, at Michigan State University. This article is republished from The Conversation under a Creative Commons license. Read the original article.


  1. STEPHEN SHEEHY | | #1

    There is no passenger rail service in the US that is comparable to service in Europe. European trains are fast and frequent. Even the Northeast corridor Amtrak service is pathetic compared to European high-speed rail.

    1. JC72 | | #3

      Never mind that the distances traveled by European trains are comparatively short which makes travel times more competitive with airlines. For example train from Lyon to Paris takes just under two hours. It's a 1 hour flight but it's over 2 hrs when you consider the time you have to set aside for getting processed at the airport. So perhaps door-to-door it's almost a wash.

  2. Dennis_the_Menace | | #2

    I would like to know how the numbers in the comparative chart were calculated. I have a hard time believing that train travel is TEN times more energy efficient than automobiles. A Toyota Camry is 3300 pounds. If it carries only one passenger (average weight 170 pounds) then the dead weight to passenger ratio is 19.4. If the Camry is carrying 5 average passengers then the ratio is one fifth that at 3.88. The average Amtrak locomotive is about 150 tons and a passenger car about 65 tons. So six passenger cars pulled by one locomotive weighs 540 tons, or 1,o80,000 pounds. If each passenger car can seat 150 people and the cars are fully loaded, the total passenger weight is 306,000 pounds making the deadweight/passenger weight ratio 3.56, a little bit better than a fully loaded Camry. These numbers seem to be in the same ballpark, not different by a factor of 10 as the chart would indicate. And I have a hard time believing that engine efficiency and different friction levels produce a 10x factor. Something just doesn't seem right here. What other data accounts for a 10x difference between trains and autos?

    1. JC72 | | #4

      Per CSX a train can move 1 ton of freight a distance of 470 miles on a single gallon of diesel.

      The real issue is the amount of time that it takes.

      1. Dennis_the_Menace | | #5

        OK, now that's a significant difference. A car maybe moves 1.5 to 2 tons about 35 miles on a gallon of gas, so let's be generous and equate that to 1 ton 70 miles per gallon. The diesel train would be 5 times more efficient. I didn't think automobile engines were so inefficient that it was possible to get 5x improvement.

    2. Expert Member
      Dana Dorsett | | #6

      The aerodynamic drag dominates the power requirements at 50mph+, and the aerodynamic drag per passenger or per ton of a train at cruising speed is probably about an order of magnitude lower than a Camry. The rolling resistance may also be an order of magnitude lower or more per passenger, but that dominates the power numbers only at low speed.

  3. SolarFIRheated | | #7

    The biggest part of the equation is stop and go. Freight traffic has the priority over passenger service as passenger trains "rent" space on the corporate rails. Once a cross country train leaves, It will try not to stop, except for crew changes and fueling. Long, non-stop trains is where the efficiency numbers are generated. A coal train of 125-150 cars holding 100-125 tons of coal can rack up some big numbers. Rail traffic has the right of way over cars+trucks, too.

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