This looks a lot like the xyproblem[1] which I have fallen prey to many times. You start out by thinking about something - highways in your case - then you formulate a model, which might turn out to work or might not. But then you make the mistake of asking about your own formulation of the problem rather than the original problem. From my own experience, even if your formulation turns out to be right, asking about the original context will usually result in higher quality answers.
Ugh I loathe this concept, although it's real. But 9 times out of 10 when you ask about a complicated problem online, which you've reduced to its simplest components because it's impossible to explain the entire context to an outsider in a text field, you'll get some internet smartass screaming 'xy problem!' to dismiss your question (this is not directed at the parent comment, just a general observation)
[1]: http://xyproblem.info/