a study from the University of Toronto confirms it: Expanding highways and roads increases congestion by creating more demand
And in a related piece, in the 1960's Vancouver abandoned an idea to add a freeway to the downtown: The Vancouver That (Thankfully) Never Was
As a result, incoming traffic to the downtown core has dropped by approximately 20% over the past decade.
Another result is Vancouver has been ranked the most livable city in the world five years running.
So to summarize - more roads lead to more people driving which leads to a less livable city. Conversely, more people capacity leads to greater livability.