The Physics and Economics of Moving 44 Tonnes at 56mph
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Re: The Physics and Economics of Moving 44 Tonnes at 56mph
#2I was reading the NASA truck aerodynamics thread earlier and realised that commercial freight is one of those fields that touches everyone's daily life (everything you own arrived on a truck) but sits in a complete knowledge blindspot for most people.
I work in fleet fuel efficiency and wrote up the foundational mental model, covering why trucks weigh what they weigh, why they're all doing exactly 56mph, why diesel is so hard to replace, and why 1% fuel savings matters when you're burning 43,000 litres a year.
This is the first in a series, there's already a 2-part deep dive on hydrogen up as well. Tried to keep it accessible without dumbing it down.
Re: The Physics and Economics of Moving 44 Tonnes at 56mph
#3I was reading the NASA truck aerodynamics thread earlier and realised that commercial freight is one of those fields that touches everyone's daily life (everything you own arrived on a truck) but sits in a complete knowledge blindspot for most people. I work in fleet fuel efficiency and wrote up the foundational mental model, covering why trucks weigh what they weigh, why they're all doing exactly 56mph, why diesel i…
Really interesting. Much thanks!
Re: The Physics and Economics of Moving 44 Tonnes at 56mph
#4Why is fuel consumption 5x more per mile but 10x more per hour, if the trucks are moving more slowly than cars?
Re: The Physics and Economics of Moving 44 Tonnes at 56mph
#5Argh the liberal admixture of different units (mpg, kg, L, hr) in the first table really brings home that this is a UK piece.
Re: The Physics and Economics of Moving 44 Tonnes at 56mph
#6Is this correct — HGVs can go faster on dual carriageways than motorways?
"UK speed limits for heavy vehicles are also more complex than most car drivers realise. Articulated trucks over 7.5 tonnes: 60 mph on dual carriageways, 50 mph on single carriageways, 56 mph (limiter) on motorways"
Not able to find a source that verifies that
Re: The Physics and Economics of Moving 44 Tonnes at 56mph
#7I was reading the NASA truck aerodynamics thread earlier and realised that commercial freight is one of those fields that touches everyone's daily life (everything you own arrived on a truck) but sits in a complete knowledge blindspot for most people. I work in fleet fuel efficiency and wrote up the foundational mental model, covering why trucks weigh what they weigh, why they're all doing exactly 56mph, why diesel i…
this is well written. thank you - you broke down the economics nicely.
I do think maybe with a hub & spoke model - big trucks move loads to hubs -- then smaller electrified trucks cover the less than 200 miles from hub to spoke. electrified smaller trucks and vans are already economical today.
you get to benefit from using diesel for long haul routes - while also - better economics on the electrified front i.e a hybrid model
Re: The Physics and Economics of Moving 44 Tonnes at 56mph
#8> At 0.5 mph differential, the overtake takes 291 seconds — over a minute of blocking the outside lane. Annoying, but it gains the driver 5.0 extra miles across a working day.
The driver gets there 5 minutes earlier in exchange for causing a 7-km tailback multiple times per day? That seems like exactly the kind of thing that should be regulated away: the truck in front is limited to 90 km/h, you're limited to 90 km/h, you should expect to travel in convoy with that truck even through manufacturing tolerances mean your limiter is actually set to 90.5.
If the 0.5 km/h is actually valuable to the trucking industry, they can invest in more precise limiters at scale.
Re: The Physics and Economics of Moving 44 Tonnes at 56mph
#9Is this correct — HGVs can go faster on dual carriageways than motorways? "UK speed limits for heavy vehicles are also more complex than most car drivers realise. Articulated trucks over 7.5 tonnes: 60 mph on dual carriageways, 50 mph on single carriageways, 56 mph (limiter) on motorways" Not able to find a source that verifies that
Sorry, got mixed up there, will amend, the 60 is for +3.5t!
Edit: Nope, despite the vehicles only being able to propel themselves to 90kmph, the speed limit is indeed 60mph (in England and Wales, Scotland is a more sensible 56mph)
Re: The Physics and Economics of Moving 44 Tonnes at 56mph
#10Is this correct — HGVs can go faster on dual carriageways than motorways? "UK speed limits for heavy vehicles are also more complex than most car drivers realise. Articulated trucks over 7.5 tonnes: 60 mph on dual carriageways, 50 mph on single carriageways, 56 mph (limiter) on motorways" Not able to find a source that verifies that
Looks like it's 50 on Dual Carriageways, 60 on motorways[0]
But...speed limiters effectively limit all heavy vehicles to 56mph[1]
Note that speed limiter are mandatory above 3.5 tons, but the legal limits change at 7.5 tons.
[0]https://www.gov.uk/speed-limits [1]https://eptraining.co.uk/news/article/hgv-speed-restrictions...