Yet there are very good reasons why public transit occupancy rates will never rise much above their current levels of about one-fifth full. Suppose you take a bus or train to work during rush hour and it seems full. But it really only seems full as it approaches the center of town. It is likely to be nearly empty when it starts its journey in the suburbs, and be nearly full only when it gets close to the city center. Over a single, one-way journey into town (or out of town in the afternoon), the vehicle is likely to average only about half full.
Plus, that bus or train has to return in the other direction, and then it could be nearly empty. Now the transit line averages just one-quarter full. Add to that all the trips made during non-rush hours, and it is hard to imagine that transit vehicles can possibly average much more than one-fifth full.