Hacker News Reader

Comment by MrDunham | Hacker News Reader

Reminds me of a story back in engineering school where a boat holding the appropriate amount of passengers at full capacity became overloaded and sank.

Turned out that the average weight of an American had increased in the decades since the Coast Guard had most recently set guidelines.

While I didn't find a link to the story, this news article [1] references a couple of boats sinking for that (assumed) reason and the Coast Guard increasing its average assumed weight per person by 25 pounds.

Makes me wonder about a lot of infrastructure for EVs. Bridges are an obvious one but I wonder about overpasses in areas that get a lot of standing traffic.

[1] https://eturbonews.com/overweight-americans-sink-old-boat-sa...

View on HN

> Turned out that the average weight of an American had increased in the decades since the Coast Guard had most recently set guidelines.

Using averages is scary for anything. There is always that day when the weight-loss club takes a boat trip, and suddenly the average doubles...

There's no incentive to spend the labor calculating what you really "need" when you can just do napkin math based on naive assumptions and be pretty sure you're within whatever safety factor the clipboard and vest types insist the thing you are dealing with be rated to.

This is all fine until the errors sync up and you get a failure where you wouldn't have gotten one if you had been spending the labor to think critically about it from the start. But hey, the safety vest people get to pat themselves on the back for the rule and implement a new one for each failure, the responsibility chain gets muddied among various parties (insurers and lawyers love that). Everybody wins! /s

Then there's the story about the man who drowned in a stream with an average depth of six inches.

-- in R. Jain, "The Art of Computer Systems Performance Analysis: Techniques for Experimental Design, Measurement, Simulation, and Modeling," Wiley- Interscience, New York, NY, April 1991, ISBN:0471503361.

This was factor in the crash of Air Midwest Flight 5481

> the plane was actually overloaded and out of balance due to the use of FAA-approved (but actually incorrect) passenger weight estimates. When checked, the NTSB found that the actual weight of an average passenger was more than 20 pounds (9 kg) greater than estimated. After checking the actual weight of baggage retrieved from the crash site and passengers (based on information from next-of-kin and the medical examiner), the aircraft was found to be actually 580 lb (264 kg) above its maximum allowable take-off weight, with its center of gravity 5% to the rear of the allowable limit.

https://en.wikipedia.org/wiki/Air_Midwest_Flight_5481

Also reminds me of elevators and looking at the nameplates there. Number of people and then divide with weight under...

Not that I worry at all, elevators have massive safety margins and sensors to indicate when they are truly overload. And even then they should be safe enough.

Were those ever intended to "match" based on an average person? I always figured that max-occupancy was for cramming 20 kids into an elevator and they will never get to the weight limit and max-weight was more for moving heavy items and maybe a lot of very obese people.

Indeed, saw a lift in London last week that had a capacity of 13 people, but a maximum weight of 800kg. That's 61.5kg/person, or 135 lbs. Not sure that's realistic in any group of adults in the western world.

What's the floor space for that elevator though?

I can't think of any elevator placard I've ever seen where the rating was something you could realistically exceed. You'd need a "some tradesmen moving a big piece of equipment" or "highschool sports team sardine packing themselves in there for amusement" type of situation.

> Turned out that the average weight of an American had increased in the decades since

I suspect that part of the reason that the teenager fell out of the FreeFall drop tower ride in that horrifying video from a year or two ago was because he was too physically big to click the actual latch on the ride's locking mechanism. Who knows if the ride operator was trained on checking people or if he was scared of a confrontation or what the situation was there, but a lot of the world's engineering might not be designed for heavy people. Unfortunately people are going to suffer because of this.

At a leisure park in the UK i once went to, the checks were performed by bored teenagers too busy hitting on each other.

The safety mechanisms worked for me but not thanks to the humans operating it.

Reply on news.ycombinator.com