Experts have shown that if you build it they will come when it comes to increasing highway width. This means that if you increase the width of a highway this will allow people to get somewhere on that highway quicker which will make more people build houses and offices to take advantage of that increase in efficiency causing the highway to quickly become jammed again and require yet more lanes.
The bottom line is that people adjust to the available transportation. An engineer told me that in Portsmouth the urban fabric is dense enough (like Portland's peninsula) that fewer parking spaces are required as people can walk to multiple errands from one parking space.
When I lived in Boston I did not own a car. When we examine our parking space needs in the city we should not prevent our streets from becoming pedestrian friendly by letting parking spaces overrule maintaining a continuous building infill street frontage. There must be a balance where folks who arrive to work can do so with some ease but buildings are allowed to strengthen our wonderful pre-auto pedestrian city.