Intuitively there feels like there should be an upper bound on this axiom. For example, imagine a highway 1 mile wide with 50 lanes going each way. That's 220 l

Intuitively there feels like there should be an upper bound on this axiom. For example, imagine a highway 1 mile wide with 50 lanes going each way. That's 220 lanes in each direction. Assume dense traffic with each car taking up 25 of lengthwise- space. A 1 mile stretch of this megahighway would have ~60,000 cars on it. At this density, the 101 between SF and San Jose would be able to accommodate ~2.8 million cars. A quick search reveals that there are only ~2.5 million cars registered in the counties this highway would run through. So while I don't doubt that this relationship ('traffic increases to fill the available road space') is true for some conditions, it's not a universal law. The real question is finding out where it starts to break down. Maybe there is some merit to building a super wide highway ;)