The sheer amount of "snake oil" bolt-on products sold to fleets in the 90s and 00s means the industry now demands rigorous third-party validation. The best open source testing I've seen comes from Mesilla Valley Transportation Services (https://www.m-v-t-s.com/certified-technologies/). They don't rely on ECM dashboard readouts or pump receipts. They run a control truck and test truck simultaneously on a track or controlled highway loop so weather, air density, and wind are identical. Anemometers on the trucks algorithmically factor out wind speed/direction, tyre temp, and weight. Tests are designed to answer the actual question rather than tick a standard's boxes. Their chief test engineer was ex NASCAR, IndyCar and F1.
My team actually tested a dual-fuel system with MVTS. The engineering was sound, testing proved a slight thermal efficiency improvement, but cheap US diesel versus the cost of the alternative fuel meant the ROI was non-existent. The physics worked, the math killed the project. (The economics work in Europe, thankfully.)
A lot of what's being discussed in this thread is already standard too. Mirrorless cabs are more the rule than the exception now (as pjc50 linked above), close-coupled trailers with gap fairings, wheel covers, under-trailer aero, all commonplace. A couple of current ones worth knowing about: the Scanias with the "Super" powertrain run a really aggressive overdrive at around 900rpm at the 90km/h (56mph)EU limit, where a conventional truck sits around 1200rpm. Requires huge low-end torque but claims 5-8%. The Mercedes Actros L claims 3% from its slippery front end alone. It is absolutely hideous though, so make of that trade-off what you will.
The biggest factor though is driver variability. All the aero and powertrain hardware in the world doesn't matter if the driver thinks they are the stig. The biggest shift in the last decade has been removing human inconsistency from fuel economy entirely.
Automated Manual Transmissions are now completely dominant in modern fleets. They shift perfectly for fuel efficiency every single time, totally capping the penalty of a bad driver. Layer on top of that Predictive Cruise Control. Modern trucks use GPS and 3D topographical maps to "see" miles ahead. The truck's computer knows exactly when to back off the throttle before cresting a hill to coast over the top, and exactly how much momentum to carry into the next dip. A human driver relying on their eyes simply cannot compete with a powertrain that knows the exact gradient of the road three miles ahead.
There are other things to consider as well when building a truck, as mentioned the maximum length limits, comfort, power price and more.
https://www.volvotrucks.co.uk/en-gb/news/insights/articles/2... : removing mirrors allows for much smoother cab airflow
https://go2stream.com/blog/aerodynamic-truck-legislation-rea... : UK legalization of fishtail-like devices
https://www.kudauk.ltd.uk/aerodynamics-explained : Kuda on the UK allowing higher loads, and therefore benefiting from extra wedge devices on the top of the cab.
I'm sure there's a lot more out there. The eventual switch to electric will probably come with another round of aerodynamic improvements to maximise range, as with cars.
https://www.colani.org/luigi_colani_Product_design_museum/Tr...
Makes you wonder if/why truck companies don't have aerodynamics experts on their payroll.
I don't understand why you put such a negative spin on this. Who loses when trying to become more energy efficient?
The reality is just that with the drive cycles and costs and tradeoffs of implementing all this it's not worth it to go this far.
Second, this sort of "round the whole thing" approach has mostly been replaced with "the simulation says we can do a 90/10 if we just do X, someone print up a block and toss it in the wind tunnel and see how it does" type approach so the result tends to be more surgical modifications and use of dead air and less "smooth out the whole thing with fairings".
I know next to nothing about trucks, and vehicles in general, but something I've noticed, and probably everyone else, is that trucks in the US looks very different from trucks in Europe, it's very easy to identify which one is a US-like truck vs a Europe-like one, because of the shape of the "cab" or whatever that part is called.
So one design has to be clearly better than the alternative, given that aerodynamics works the same all around the world, but still the designs are uniquely... unique.
But why is it like this? If trucks were designed for aerodynamics, shouldn't one of the designs have "won" by now, or are they truly equal in terms of aerodynamics?
Because aerodynamics is not the only concern the manufacturers are thinking about.
The difference is in the regulation. The maximum allowed length for a semi-truck is shorter in the EU than in the USA. And since they both want to transport the same length of container the European truck had to be designed shorter.
My dad used to drive concrete delivery trucks in europe. Most were the european arrangement with the cab over the engine, but one of them he drove had the American style long-nose. It was so unusual that they nicknamed the truck after this feature. They called it "csőrike" which is hungarian for "the one with the beak".
He also said it was a lot easier to maintain the long-nosed vehicle. With the european cab-over design you have to first secure everything in the cab and then tip the cab forward to have access to the engine and transmission. While with the long-nosed concrete truck you could just open the hood and get to work.
Front-engine designs are much easier for a mechanic to work on. Cabovers are much more length-efficient.
If we were overly concerned with aero, you would see multiple unit designs like Turnpike Doubles or triples (or in an extreme, Australian road trains) - https://www.fhwa.dot.gov/policy/otps/truck/wusr/chap02.cfm. For areas where we're too operationally locked in to singles, you would see 60 footer container trailers like they have in a few states in the western US.
You would also, in 2026, hopefully see multi unit designs where the trailers are self-propelled vehicles that can separate and dock automatically at half a mile an hour.
Videos can show the difference visually and note some wider patterns where Euro trucks continued to evolve in other ways -
https://www.youtube.com/watch?v=WpenLsHEHaY
https://www.youtube.com/watch?v=GZRHjhoURz0
https://www.youtube.com/watch?v=LVDIGe0y-to
https://www.youtube.com/watch?v=C0iUiyQOn5E
Are they? I mean by intuition I'd assume the same, but seems it isn't considered so black and white as far as I can tell, I can find reasonable research pointing both ways, but I'm guessing you're basing that on something more conclusive? Mind sharing the link so I could too read up on it?
TFA literally has NASA doing research and seemingly reaching a different conclusion than "long-nosed trucks are vastly more aerodynamic", seems to be about more things than just the hood, and those can be/are optimized on both variations.
But again, I know little about all of this, but would welcome being educated on it more.
Also American truckers do a lot more long-haul work and American roads are noisier, so they prefer being more insulated from the engine.
The air may be the same everywhere, but roads and safety laws aren't.
One of them must be better aerodynamically though, must'n it?
Furthermore Europe has relatively strict speed limits on trucks, which makes aero something of a lesser factor since drag grows to the square of speed: european trucks at european speeds have a pretty significantly higher efficiency than US trucks at US speeds.
But that goes directly against TFA, doesn't it? The final image is closer to the European design than the American one? Or am I misunderstanding the article?
> they are potenitilly safer
Maybe for the occupants, but for everyone else they seem strictly worse, not to mention the visibility much be much much worse, making it a somwhat iffy tradeoff.
https://www.ccjdigital.com/regulations/article/15291029/acha...
This is the most recent news I can find about them, though, so unclear if these engines will ever be produced for road vehicles:
https://www.govconwire.com/articles/ga-asi-david-alexander-a...
See also: https://achatespower.com/resources/
I was hoping we'd see these engines running generators in Edison trucks one day.