> would increase fuel economy by 15-25%
Makes you wonder if/why truck companies don't have aerodynamics experts on their payroll.
> would increase fuel economy by 15-25%
Makes you wonder if/why truck companies don't have aerodynamics experts on their payroll.
They absolutely do design trucks for aerodynamics. Fuel economy is a huge avenue of competition for semi trucks.
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".
> They absolutely do design trucks for aerodynamics
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?
> If trucks were designed for aerodynamics, shouldn't one of the designs have "won" by now,
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.
Mostly length regulation, and the prevalence of "sleeper" cabs and other trip length related factors. Economies are a little more self contained and less overland-transcontinental in Europe as well - the amount of freight going Rotterdam to Istanbul is a lot smaller than the amount of freight going LA to Boston, and it's a significantly shorter journey regardless.
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
https://www.youtube.com/watch?v=_ILjQpEX_8Y
https://www.youtube.com/watch?v=KxRKFO_OiQM
This is down to regulations. The total length of the vehicle is capped in Europe so to get more useful cargo space, the cab is shortened to a cab over engine design with a completely flat (short) nose. Making the cab longer or more pointy/aerodynamic cuts from the length available to the trailer. There’s usually more money inside the trailer than in the fuel savings so everyone accepted this solution.
An other important regulation is truck speed limits, because drag grows to the square of speed.
The energy of a potential impact is the main driver of that regulation. Also increasing with the square of the speed, and with the (sizable) mass.
That does not change the result: drag is much less of a concern for trucks in Europe than it is in the US.
> important regulation is truck speed limits, because drag grows
No I just meant that drag was a second thought when the regulation was conceived on either side of the ocean. The regulation was not created "because of drag". The main driver was road safety. Efficiency and pollution were secondary. There are other ways to achieve them like improving aerodynamics or power trains, and much of this cost is paid by the freighter alone. This is why speed limits didn't increase as trucks got more efficient and drag went down. Because there's no way to reduce the potential energy of a 40-50t vehicle (or up to almost 90t Finland) travelling at 130km/h.
> No I just meant that drag was a second thought when the regulation was conceived on either side of the ocean.
Again, not relevant.
> The regulation was not created "because of drag".
That is not a claim I made. Please do not involve me in your fights against the ghosts you made up.
All trucks have standard shipping container trailers. Europe has strict length limits for the overall cab/trailer that preclude a hood in front of the cab. There is great resistance to changing the law, even though long-nosed trucks are vastly more aerodynamic, because the law provides protection for european truck makers from American competition.
> even though long-nosed trucks are vastly more aerodynamic
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.
Even though several Europeon truck makers compete is America. they have the designs and ability to compete
My understanding is that in Europe regulations focused on the length of the whole vehicle, whereas in America the length of the cab and trailer were regulated separately.
Also American truckers do a lot more long-haul work and American roads are noisier, so they prefer being more insulated from the engine.
This is a bit counter intuitive, but Euro style cabovers are much quieter inside than a 'conventional'. Plus cabovers can have air spring suspension, they're often more comfortable. The downside is much less space inside, which is a big deal for the long haul drivers in the states, whereas in europe, they rarely do more than a month at a time.
AFAIK nothing precludes having air bags on conventionals, it’s just optional / uncommon whereas it’s completely expected on euro trucks.
To clarify, the air bags isolate the cab from the chassis.
There is also suspension between the axles and the chassis which is 99% of the time air on the rear, leaf spring front.
I haven't come across a cab that is suspension isolated from the frame of a conventional, even though the axles are on air. Theoretically as the driver is in the sweet spot of a much longer wheelbase, rather than sitting directly over an axle.
> I haven't come across a cab that is suspension isolated from the frame of a conventional, even though the axles are on air.
They are very often on a simple suspension. The cab will have a pivoting mount at the front and sit on air springs in the back.
Did a bit of research: https://news.ycombinator.com/item?id=47121031 - different countries have different legal requirements, despite air being the same everywhere.
Judging by the images only, those are all the ones I called "European" trucks though, the American ones are much longer. Is that also regulated so European trucks aren't allowed in the US and American ones aren't allowed in Europe? Because here in Europe it's really uncommon to see the US ones, and I'm guessing it's the opposite in the US?
One of them must be better aerodynamically though, must'n it?
Europe has length limits on the entire thing, so US trucks would require shorter trailers, which nobody really wants. Euro trucks also have significantly smaller turning radii, which makes navigating european cities and country roads… feasible.
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.
I could be wrong, but I thought the US had a mostly-national speed limit of 55mph, while the UK truck speed limit is 60mph, and the French truck speed limit appears to be 90kmh (56mph)
US speed limits are highly variables, they’re generally 55 in the north-east but on the western half they’re 65 to 70, and 75 in TX.
And that assumes the speed limits are respected at all, but the EU has required a hard 90kph limiter since 2005, tampering with the limiter is a criminal offense, so is tampering with the (also mandatory) tachograph which would reveal the first.
So while nothing prevents speeding up to that (and it very much happens) going higher becomes extremely dicey.
> US speed limits are highly variables, they’re generally 55 in the north-east but on the western half they’re 65 to 70, and 75 in TX.
I fear even that is misleading. Yes, the speed limits on undivided highways are often 55 in the north-east (or even 50 in a couple), but the speed limits on divided highways are all higher, ranging from 65-75 mph. See the two maps on the top right: https://en.wikipedia.org/wiki/Speed_limits_in_the_United_Sta.... I suspect that the majority of truck miles are on divided highways.
A number of the major freeways immediately around Boston are 55. Almost nobody actually drives slower than +10 mph. If you go 55 in the slow lane you'll get passed by other people in the slow lane!
I've seen truck speed limits of 55 pretty much everywhere I've been except Texas, though.
Is shipping either design of large truck across the ocean even feasible? I'm thinking they might be too tall for standard car carrier ships, but IDK.
It’s not hard. There are European cabovers in the US (see the Bruce Wilson YouTube channel).
American designs are aerodynamically better. they are potenitilly safer (crumple zone) though I haven't seen any safety studies.
> American designs are aerodynamically better
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.
You're misunderstanding the context. The US at the time regulated truck length to a patchwork of shorter lengths state by state and so cabovers proliferated and that's what NASA chose as a base. So if you start with that and "add aero" it's going to trend toward what looks like a modern European design.
There are no crumple zones in a truck really.. You have straight frame rails. I guess the cast iron engine block gets a little crumply if you hit it hard enough..
Any space becomes a crumple zone - rails are great at that, but it is still something. Though as I said - I have never seen a study of relative safety.
In a cabover truck you're the crumple zone >_<
> despite air being the same everywhere.
The air may be the same everywhere, but roads and safety laws aren't.
Those figures are from the 1970s, when presumably there was a lot more low-hanging fruit. Still, I wouldn't be surprised if they invest a decent chunk into computation aerodynamical work as part of their body design.
You’re also touching on a rather large ignored issue in this article, that this NASA truck aerodynamics project was directly connected to the 1973 oil crisis and a government wide effort to reduce oil consumption, not just some epiphany by some guy on a bike.
Both can be true. Sounds like the classic: necessity is the mother of invention
I don't understand why you put such a negative spin on this. Who loses when trying to become more energy efficient?
Part of the issue is the extreme constraints imposed on designers by road regulation, another is simply that the majority (75%?) of drag reduction is in a fishtail that needs to go on the container, the part of the truck that gets left behind at the loading dock, that is often not "owned" by the person who owns the truck.
They do, look for some semi-trucks on long haul routes, they have trailer skirts and/or trailer tails.
Because the individual logistics companies are not developing the trucks. The aerodynamic properties of a truck are mostly determined by the model/brand, and this is a huge consideration at companies like Scania, Volvo or Mann. Not so much at the individual logistics companies.