It also appears to be open source, so perhaps you can open a pull request with your improvements based on your cartographical experience.
Looks neat!
https://github.com/anvaka/city-roads
Edit: it outputs SVGs and you can try it online. Anvaka (author) has other really cool dataviz projects.
Salem, OR and Salem, MA
Portland, OR and Portland, ME
Springfield, IL and Springfield, MO
Dallas, TX and Dallas, GA
Is there a reason you’ve defaulted to PNG that I’m missing?
I have tried adjusting -d, but it only affects the scale.
Here is the command I used: python create_map_poster.py --city Leuven --country Belgium --distance 4000 --theme sunset
-d should be approx. 10k to 14k given the size of the city. You can give it a shot.
It doesn't look like the orange and blue colors are part of the theme definitions, so the rendering library may be using some default values. This is why they are rendered in the same color on images using different theme files.