I was chatting, this weekend, about how trolleys became obsolete when cars and buses developed. Buses are far more flexible, subways are quicker, and people love their cars. The Model T killed the trolley. With car traffic, trolleys are not much faster than walking. I have to admit, though, that the trolleys - and subways - in Vienna are great and easy for a tourist to figure out. However, Vienna has little car traffic.
I missed this one: Was the Rise of Car Ownership Responsible for the Midcentury Homeownership Boom in the US?