The author calls out that they aren't a civil engineer, and the bridge example wasn't meant to necessary reflect reality. > If you were designing a car today,

The author calls out that they aren't a civil engineer, and the bridge example wasn't meant to necessary reflect reality. > If you were designing a car today, and were willing to have 25% more weight, you probably could design it with a slide rule. You'd get a 1954 Buick Roadmaster, a sedan with a curb weight of 1983 kg. Being 25% heavier than necessary is likely far too much. You could definitely design a car using analog tools and calculations to within <5% of the minimum requirements. This is a great example of where too much precision is a bad thing! A 1954 Buick Roadmaster had a curb weight of 4,430 lbs. Choosing a random modern car, a 2022 Toyota Camry has a curb weight of 3,310 lbs. Assuming those as a baseline, each 1% of weight due to "overprovisioning" would be 44.3 and 33.1 lbs respectively. Lowering the load capacity of the vehicle by 5% would mean a 221.5 lb reduction in capacity for the Roadmaster and 165.5 lb for the Camry. You have to account for not only the precision of your design, but also the precision with which it is used. I seriously doubt I could estimate to within 200 lbs how much the combined weight of all occupants and cargo in my vehicle is at any given time. It's therefore fair to say that the use case for a car is not estimated to within 5% of reality - so the car must be overbuilt by some margin of >5% to account for that. If the precision of the intended use case is that high, spending additional time to reduce vehicle weight to <5% of the target capacity is wasted. It's better to make it a bit heavier than strictly necessary than it is to spend the resources to know precisely how heavy it needs to be to meet an imprecise requirement.