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What is the "Correct" Speed Limit? – YouTube version
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this post was submitted on 05 May 2024
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Not Just Bikes
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Towards the end of the video he addresses the point that the optimum speed of cars is around 60(or I thought it was 70).
This argument doesn't apply here because that figure is for a car traveling at a constant speed on a straight, flat road with no wind. E.g. a freeway/motorway. In a city, a significant amount of the energy is used to speed up and slow down at intersections.
Remember the kinetic energy formula, Ek=1/2 mv^2 . That tells you that accelerating a car to twice the speed takes 4 times the energy, or in other words it takes 4 times as much fuel to get to 60 as it does to get to 30.
This extra energy to get up to speed is going to far outweigh any benefit from less rolling resistance at 60 compared to 30.
fwiw, Lemmy actually supports both subscript and superscript, though the syntax is a little weird if you're used to Reddit.
~text~is subscript,^text^is superscript. (Unfortunately support on mobile clients—even Jerboa, made by the official Lemmy devs—is rather lacking.)E~k~=1/2mv^2^
But yeah, that's a really good point. I wonder how long you'd have to be travelling at 60 km/h to make that extra acceleration worth it in terms of fuel efficiency.
As a separate question: people would probably often be willing to sacrifice their fuel efficiency if it meant substantially shorter travel times. I wonder how much this would actually work. On highways it's definitely going to be a huge factor, but on the sorts of inner-city stroads that are usually posted at 60 km/h, I suspect you'll probably arrive at most of the same red lights accelerating up to 40 km/h as someone getting all the way up to 60 would. Would be an interesting experiment to conduct.