[jerven]

4 people, for a short term stay is about where it starts to make sense to ride share. Long term, you would have an longer term pass, vastly reducing the cost of a busride, and you would often travel in smaller groups. So in my experience there are times when bus/tram can be much faster and convenient than a car. Of course there are many cases where it is the other way round (and going out of the cities that ratio changes dramatically for a car). Good city design tends to favor a ratio in favor of public transport over cars.