Independent of the cars thing....
Now you make me wonder about the density of buildings on places of high temperatures/desert like places... Like more density means more shadowed places for people to walk etc... But it also blocks more wind and air movement so maybe is more shadowy but it traps more the heat....
Now I wonder what is best for the weather situation and people living there.
You should check out Córdoba, Spain. It has a lot of narrow streets and it's fully walkable even in summer. Like you said the streets are shadowy and there's also free tap water fountains everywhere. It's not a desert city but the record temperature in Córdoba is 46.9 C (116.5 F), and regularly reaches over 40 in summer. Here's some photos