I’ll start with a brief discussion about the comparative fuel efficiency of heavy-duty (HD) trucks and freight railroads in the United States. We’ll then have a six-question quiz (for you, my readers) followed by some concluding thoughts.

Keep in mind that fuel efficiency is measured differently for HD trucks and for freight railroads:

• HD trucking’s measure is miles per gallon of fuel (MPG), so any “improvement” produces a higher number over time.
• Freight rail’s measure (reported by the railroads) is gallons of fuel per thousand gross ton-miles (Gal/1,000 GTM or G/KGTM), so any “improvement” produces a lower number over time.

Because the two modes use different measures of fuel efficiency, a direct comparison of HD trucking (MPG) and freight rail (G/KGTM) data is difficult to accomplish. In the past, freight rail’s fuel efficiency has been described as being at least four times “better” than HD trucks. In fact, in June 2023, the Association of American Railroads (AAR) raised freight rail’s energy effectiveness from more-than-400 to “… almost 500 ton-miles per gallon of fuel,” which is great news.

There has been one analysis and report, however, that “normalized and compared” HD truck and freight rail fuel “economies”. It was funded by the Federal Railroad Administration (FRA) in 2009 (yes, that was 15 years ago) “Comparative Evaluation of Rail and Truck Fuel Efficiency on Comparable Corridors” report. The report produced a good baseline look at the comparative performance of various HD trucks (tractor with dry van, reefer trailer, flat bed, etc) compared to freight trains moving double-stack containers, TOFC, mixed freight (“box car”) or solid (“unit train”) shipments of automobiles, on an equivalent ton-miles per gallon of fuel basis. Ironically, the year 2009 is coincidentally very important in this discussion because of an ongoing extensive program (started in 2009) to improve HD trucking fuel efficiency.  We’ll discuss that HD truck R&D shortly.

Here are two illustrations from the 2009 FRA report showing freight rail fuel efficiency compared to HD trucking, with both modes recalculated on the “ton-miles per gallon of fuel” basis. The first chart shows (as of 2009) the validity of the historic “4-times better” freight rail versus HD trucking conclusion, for different types of freight car types and HD trucks.

Here are two more charts from the 2009 FRA report, on the left showing average HD truck fuel efficiency 1990-2006, and on the right showing freight rail’s efficiency 1988-2006: 

As you can see, up to 2009, HD trucks were “flat lined” (and getting slightly worse) at about 5.5 MPG, and freight rail was continuing a long pattern (albeit at a very low rate) of fuel efficiency improvement. In fact, if you take the rail data and calculate annual improvement of G/KGTM … rail was improving at about 1% per year. (As you will see later, rail’s recent improvement has been “lower” and in some years negative.)

Back in 2009, we could rightfully say “HD trucking has had little-to-no improvement in fuel efficiency, and freight rail has made a long-term modest improvement.” But that was in 2009.

SUPERTRUCK (IF YOU NEVER HEARD OF IT, BEST YOU LEARN NOW)

I mentioned that 2009 is of importance, because it was the beginning of a major public-private co-funded (50:50 basis) R&D program called “SuperTruck”. The U.S. Department of Energy (DOE) and HD truck manufacturers and their suppliers started a chain of multiple R&D projects. The “private” side of the partnership has involved the tractor and semitrailer manufacturers, and suppliers of truck engines and transmissions, tires, aerodynamic accessories and even hardware to decouple parasitic loads like water and oil pumps from the engine crankshaft (i.e., “pumping on demand” instead of all the time, and reducing cab air conditioning energy by 50%). In other words, revolutionary changes to HD trucks.

• SuperTruck 1 (2009-2016) developed 20+ technical improvements (largely to reduce aerodynamic drag) that are now incorporated into all new tractors-and-semitrailers (plus retrofits). ST1 was focused on a 50% improvement in HD efficiency (over the baseline year 2009, which happened to be 5.5 MPG). For additional details click here. Here’s an image of a HD truck with aerodynamic treatment to reduce the historic “blunt body” air resistance:

• SuperTruck 2 (2016-2023) boosted the improvement in HD truck efficiency (again compared to 2009’s 5.5 MPG) from 50% to 100% (i.e., “doubling” the MPG to roughly 11 MPG). ST2 focused largely on high-efficiency diesel truck engines (with thermal efficiencies as high as 55% … compared to new Tier 4 locomotive engines achieving 42-44% thermal efficiency), hybrid transmissions, etc.
• And now SuperTruck 3 (2023-2027) is paving the way for a 75% reduction in heavy-truck carbon emissions (preparing for decarbonization of HD trucks) and further reductions in oxides of nitrogen (NOx) and particulate matter (PM) by developing battery-electric and hydrogen fuel cell propulsion for heavy duty tractors. For details please see “Fact of the Week #1346, June 10, 2024: US DOE SuperTruck 3 Initiative Seeks to Reduce Medium/Heavy Truck Greenhouse Gas Emissions by 75%”, on the internet.

I recently received an email from Dr. Siddiq Khan (DOE’s Manager Super Truck & Lead, Rail Decarbonization) confirming that the newest HD trucks can now achieve at least 11 MPG. He also pointed out that Navistar in December 2023 demonstrated a superb 16 MPG with its “International SuperTruck II” tractor-and-semitrailer design (see the magazine excerpt below from this article):

How quickly will these improvements in HD truck fuel efficiency produce bottom-line results? It will happen as truck operators acquire new tractors and semitrailers. The average “1^st owner” life of tractors and semitrailers in the U.S. before fleets are replaced is one decade (although the largest fleets have been seen to wholesale replace their entire tractor fleets in as little as two years to avoid major engine-and-transmission overhauls, cascading those tractors to lower tiers of fleets).

Let’s take a calm but sobering look at what we know and what is being discussed (and proven) regarding HD truck fuel efficiency:

• Up to 2009 HD trucks could “only” achieve about 5.5 MPG.
• The newest HD trucks today can now achieve 11 MPG (2x better in 14 years).
• And some new HD rigs have demonstrated as much as 16 MPG (well past the ST2 goal).
• Even 20 MPG is now a “discussion topic.”

Do these numbers get our attention? SuperTruck also facilitates the transition of heavy-duty trucking into compliance with the Environmental Protection Agency (EPA) “Greenhouse Gas Emission Standards for Heavy-Duty Vehicles” released in April 2024. That regulation requires 30% of all heavy-duty trucks be zero-emission by 2032.

FREIGHT RAIL FUEL EFFICIENCY (WHERE HAVE WE BEEN, WHERE ARE WE HEADED?)

Now let’s “change lanes” and look at freight rail’s fuel efficiency. My former Union Pacific coworker Wayne Kennedy (Kennedy Consulting in Omaha, Neb.) has been tracking the fuel efficiency of the seven (now six) Class I railroads since he and I left UP in late 2018, using public data. Here is Wayne’s latest chart showing Class I industry-average fuel efficiency for 1997-through-2023:

Focusing on 2009-2023 (to compare against HD trucks since the start of SuperTruck), Wayne’s data shows:

• Freight rail achieved 1.19 G/KGTM in 2009 and reached 1.07 G/KGTM in 2023, a 10% cumulative improvement or 0.7% cumulative annual improvement.
• New HD trucks achieved 5.5 MPG in 2009 and reached 11.0 MPG in 2023, a 100% cumulative improvement or 5% cumulative annual improvement.

Here is Wayne’s chart showing rail’s weighted annual improvement in G/KGTM, year by year, since 1998. The long term cumulative annual improvement over the past quarter of a century has been 1.07% per year (the dashed red line) and in fact the recent annual results have “gone negative”:

Now that we’ve discussed the background information, here is your “fill in the blanks” quiz. Spoiler alert: To save print space and save you time, I’m showing the questions and the answers:

1. HD truck averaged 5.5 MPG in 2009 and 11.0 MPG in 2023, a 100% cumulative improvement, an annual improvement of 5.0%.
2. Rail averaged 1.19 KGTM in 2009, and 1.07 G/KGTM in 2023, a 10% cumulative improvement, an annual improvement of 0.7%.
3. Maximum new HD truck fuel efficiency in 2023 is 16.0 MPG, 190% better than the average in 2009 and 45% better than the ST2 goal.
4. Cumulative improvement in HD truck MPG 2009-2023 has been 100%.
5. Cumulative improvement in rail G/MGTM 2009-2023 has been 10%.
6. SuperTruck 3 is developing battery and fuel cell propulsion for HD trucks.

WHAT DO THE NUMBERS TELL US?

1. We’ve been improving our fuel efficiency, but our rate of improvement over the past 14 years has been only about 1/10 that of HD trucks.
2. HD trucking is becoming ever more fuel efficient thanks to the three SuperTruck programs since 2009 that will have plowed more than $600 million into commercially successful reductions in the fuel consumed by trucks.
3. Overall, the SuperTruck programs have created about two dozen technological changes that have been commercialized in new HD tractors and semitrailers (which generally have “1^st owner” service lives of under a decade).
4. HD truck suppliers, with assistance from the DOE, are in the final SuperTruck 3 program developing battery-electric and hydrogen fuel cell propulsion plants for tractors, to assist reaching net-zero carbon operation (and another big reduction in HD exhaust emissions by reducing the use of diesel engines).

Can freight rail follow the same path as HD trucking? To some extent, yes, provided a clear industry and supplier consensus (and funding … hello, DOE) to focus locomotive, freight car and operational R&D. But freight rail is still radically different from rubber-on-pavement trucking, so future technological improvements for rail will have to be tailored specifically to rail, largely not adapted from trucking. Unlike HD trucks, our locomotives and freight cars are historically designed, built and financed for lives measured in multiple decades. (A new freight car today will likely be unchanged and interchangeable until the year 2074 (or 2089 with fatigue testing and analysis.)

THE FEVER THAT WON’T BREAK

Time is passing, very quickly. We’ve multiple meetings, presentations, articles and discussions about freight rail fuel efficiency over the past decade. And now we have data clearly showing how HD truck has improved.

In closing this article, let’s go back to 1965, five years after U.S. railroads dieselized and the “golden era” of heavy-duty trucking when highway speeds and truck drivers weren’t controlled or regulated as they are today. I’m not praising trucks or all-day-and-night driving back in 1965. But that year a brief-hit single song, “Freightliner Fever,” written by Truman McCoy Lankford landed on the radio charts.

The second verse of that song is a great metaphor for the SuperTruck revolution:

Now, there’s a railroad a-runnin’ by the highway out in Santa Fe
And I passed an old freight train makin’ his run the other day
The engineer said to the fireman, so pale
He’s blowing this freight train off of the rails
He got the fever
He got the freightliner fever

SuperTruck has got the new fever. And it likely won’t ever break.

Further Reading: Alternative Energy Efficiency: ‘Does it Pencil?’