The first is car centric, with lots of roads and deep set backs. These cities are amenable to bike and public transit transformation in terms of space, but usually have political resistance to change. These cities will be the easiest to add extra bike infrastructure to, once a political mass is reached. My current city is like this, and the current bike path master plan is trying to add enough paths for 96% of the city to be near bike infrastructure (currently it’s 10%).

The second category are really dense, and do not have the space for any extra lanes. But these cities dedicate a huge amount of space for parallel parking. Theoretically the city could remove parking for bikes, but practically this means purposefully pricing people out of car ownership, which is obviously unpopular. These cities should focus on public transit, which is by and far the most space efficient way to move people. For a lot of these cities this is less about installing new lines, which is expensive, but about making the existing system feel cleaner and more dignified. It will always be hard to make improvements when even the crappiest sedan is considered a step up from taking the subway to work.