I am making a FPS/RPG exploration game (first person shooter RPG, think first person Zelda with guns), and one of the main focuses is a large city.

Due to the fact that I am an indie dev, and don't have the time to make an entire city, and also the fact that I have previous experience with procedural generation (not cities though), I've decided that I'd like to use it to save time.
I was reading this post, and it said to make a city you need:

1. City centers: Pick some points of the still empty map as main traffic nodes. They should be evenly distributed around the map
2. Highways: Connect the main traffic nodes to their neighbors and to the outside world using major roads.

(And the rest from the post.)

An example of what I’d like is this:

My question is:
How do I calculate which city centers to connect to each other, to provide a realistic city?

By distance?
Add a weight or size to each one?
Only allow each centre to have 2 connections?