I wonder if the rise of Uber will affect this.
When I lived in Seattle, I noticed that a lot of people didn't commute to work via car but had one anyway, usually for one or two trips per week. Public transportation (buses and later light rail) were pretty good from about 8 a.m. to 7 p.m. or so during weekdays but were horrible the rest of the time. Bikes could be used intermittently.
Uber does an amazing job of filling in the gap. Last time I visited Seattle, I was struck by how some of my friends had given up cars, despite rising incomes, largely due to Uber. Uber may play a key role in getting rid of a lot of cars that are only marginally utilized, since it appears far more reliable and friendly than taxis—virtually all Seattlites who have to use Seattle taxis hate them. This has environmental and other implications.