> "you've just thrown out the other advantage of metric: universality" Nope. I've done the opposite. Let me explain: when you set up a traffic flow equation

> "you've just thrown out the other advantage of metric: universality" Nope. I've done the opposite. Let me explain: when you set up a traffic flow equation (or many other complex equations), you don't write it in terms of meters or feet or any other supposedly universal unit. You write it in terms of whatever the natural scale is -- whatever makes the math simplest. (You might define the average car length as "1", for example.) Then once you've finished solving your equations, you can rescale everything in whatever units are most familiar to the audience you're presenting to.