In most large US cities, the transit mode share for commute trips is stagnant. If it’s increasing, it’s not by much – for example, Seattle is up from about 7% in the early 2000s to 8.7% in 2009. However, in Canada and Australia, there are multiple cities where the transit share has increased by 2-4 percentage points over the decade; all numbers are 1996-2006. Melbourne had the highest increase, from 13.1% to 17.7%. Car use declined by a little more than transit increased, at least in Canada. (Any information about similar increases or decreases in Europe and high-income East Asia will be appreciated.)
Even Melbourne’s performance is not going to be enough by itself to get car use to sustainable levels. Much more is needed: less distance traveled per car, less driving and more walking for non-work trips, and higher vehicle fuel economy, to name the three most important. But in four decades a city with Melbourne’s performance can raise transit use by 18 percentage points by 2050 and cut car use proportionately, and in conjunction with the other three points, it could make a serious dent in greenhouse gas emissions.