Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

The Physics and Economics of Moving 44 Tonnes at 56mph

mikeayles.com

Post reply on HN
Print view View original

81–90 of 123 posts

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#81

Post by 542354234235 »

dmurray wrote: post #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…

It kind of annoys me that the article says the people trapped behind the trucks are just inconvenienced, but the truck driver gains time and money. Considering commuting to and from work is what most people are doing on the road, that is exactly time and money. It really could be seen as truck drivers stealing dozens, if not hundreds, of minutes from other drivers to give themselves 5 minutes.

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#82

Post by yabones »

Maybe they should give the trucks a "turbo boost" button that lets them increase speed by something like 5 KM/hr for 120s every 30 minutes. Just enough to allow truck drivers to pass now and then without causing these types of log-jams on the highways, without causing safety problems. I'm sure there's a more correct combination of speeds and times than this.

Sort of like the silly "boost buttons" on the Honda CR-Z [1] or the Elantra N [2], but just lifting the speed limiter for a bit...

[1] https://en.wikipedia.org/wiki/Honda_CR-Z#Powertrain

[2] https://en.wikipedia.org/wiki/Hyundai_Elantra#Elantra_N/Avan...

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#83

Post by aitchnyu »

mikestew wrote: post #72
aitchnyu wrote: post #56

Tangential, do vehicles detect motion by crosswind or road camber and compensate? I saw some social media post of lots of trucks toppled over by crosswind.

Our camper van (which is a tall sail) compensates for sidewinds. Other RVs can have this feature as well, though often as aftermarket fitment. Pretty neat when it works, “man, sure is windy today, but this van is a lot easier drive in the crosswind than our old RV. Oh…” But an RV is not a semi tractor-trailer setup. In fact, crosswind compensation is something I’ve only seen on RVs that don’t involve a trailer (Class…

Seems very integrated into the vehicle. Who is selling aftermarket versions?

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#84

Post by mikestew »

aitchnyu wrote: post #83
mikestew wrote: post #72

Earlier quoted context omitted.

Our camper van (which is a tall sail) compensates for sidewinds. Other RVs can have this feature as well, though often as aftermarket fitment. Pretty neat when it works, “man, sure is windy today, but this van is a lot easier drive in the crosswind than our old RV. Oh…” But an RV is not a semi tractor-trailer setup. In fact, crosswind compensation is something I’ve only seen on RVs that don’t involve a trailer (Class…

Seems very integrated into the vehicle. Who is selling aftermarket versions?

I'd swear I've seen such systems advertised in the appropriate magazines for large RVs (Class A "tourbus" RVs), but for the life of me a web search brings up nothing. For now, assume I hallucinated such a thing (or maybe what I think I saw was actually just an old-school steering stabilizer that advertised "crosswinds!".)

And you're right, it does seem that the systems are integrated. For example, Mercedes' system for the Sprinter applies the brakes on one side to compensate. Seems like something would need to tie into the CAN bus to pull that off. Not that aftermarket couldn't do the same, but is that functionality even available on a 43' pusher diesel?

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#85

Post by matsemann »

dzonga wrote: post #7
mikeayles wrote: post #2

I 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 hybr…

And I'd rather have last-mile trucks with Direct Vision, no blindspots etc driving around city streets, backing into stores etc., than huge 44 tonne long haulers that can maul pedestrians in an instant.

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#86

Post by tobinfricke »

JoachimS wrote: post #66
cbdevidal wrote: post #59

Earlier quoted context omitted.

Seems to me that the slower truck is really the inconsiderate one here. If you’re already slower, tap the brakes a little and let the other guy slide in.

Or just take the foot of the pedal for a while.

Seems like a game-theoretic problem

Taking their foot off the gas for a second only hurts them

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#89

Post by digitalPhonix »

mikeayles wrote: post #2

I 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…

You open with

> Every driver in the UK has experienced this. Most assume the truck driver is being inconsiderate.

But then go on to explain how that is exactly true. The truck driver is taking time from *all* drivers on "roughly 4.5 miles of dual carriageway", just so that they can end the day 5 miles ahead.

> The five minutes of inconvenience to you saves them meaningful time and money over the course of a day.

It's five minutes of inconvenience to *everyone* on that 4.5 mile stretch of highway that nets the truck 5 minutes (5 miles ahead at ~60 mph). That's a very selfish and inconsiderate outcome.

Re: The Physics and Economics of Moving 44 Tonnes at 56mph

#90

Post by pinkmuffinere »

> The truck cannot go faster. Floor the throttle at 56mph and nothing happens. The fuel injection is electronically capped.

Man, that's kindof scary -- if for some reason the truck legitimately needs to go faster (eg, escape a warzone, a flood, a wildfire), it cannot do so. I'm sure this was a calculated design decision, but on the surface I'd prefer if the speed was logged and then checked at regular intervals (perhaps with automated reader). That would also allow for easy updates to the limit, tighter restrictions in specific areas, etc. I wonder what all the factors going into this design decision were.

Post reply on HN