It sounds like what you are thinking of is a spectrum more in the sense of a range, where one end is "least" and the other "most". There was an interesting article[0] making the rounds a few years ago arguing that it's more like the color spectrum. While there is an underlying linear value to the color spectrum in the wavelength, you don't really talk about red being "more" of a color than blue just because it has longer wavelength. Instead, we talk about combining, and sometimes mixing, colors. The article author argue that the autism spectrum is like that; it's made up of individual traits that make a whole. As I understand it, diagnosis is in part looking at the number of those traits that a person exhibit. Severity would then be a perpendicular axis to the spectrum of traits.
Of course you can. Just design the area for walking and biking and let the motor vehicle traffic flow around that.
A car driver is not nearly as inconvenienced by an incline as a pedestrian or cyclist would be. If we don't want to do more in depth changes, then at least we could just let motor vehicle traffic tunnel under or bridge over foot and bicycle paths instead of the other way around.
[0] https://neuroclastic.com/its-a-spectrum-doesnt-mean-what-you...