I like Jarrett Walker. He does come at the problem from a certain perspective though -- he wants to solve problems with mass transit. Just like he talks about there being immutable laws of geometry, there are some immutable laws of transit. Mass transit fundamentally depends on having a lot of people who want to get from point A to point B, all at the same time. Since this is never true, you have to relax the requirements. You can make people wait until there are enough of them, you can make them walk to or from a stop, you can make them detour, slow down, stop and then speed up to let others get on and off, and you can make them switch vehicles. Fundamentally those are your options given some set of vehicles, whether they're planes, trains, or automobiles. All forms of transit exist on the tradeoff surface between these possibilities. As population density goes up, it's easier to find lots of trips that are close enough in the five dimensional space of origin, destination, time.
Where I perhaps differ from Jarrett is that I see no problem in having transit options that have one or two people per vehicle. The 2-5 person capacity mass transit vehicle has been a very underexplored space because someone has to own it and someone has to drive it. Services like Uberpool and Lyft Line are exploring this because smartphones make it possible, and this will only increase when you don't have to pay someone who isn't riding to operate the vehicle.
Where I perhaps differ from Jarrett is that I see no problem in having transit options that have one or two people per vehicle. The 2-5 person capacity mass transit vehicle has been a very underexplored space because someone has to own it and someone has to drive it. Services like Uberpool and Lyft Line are exploring this because smartphones make it possible, and this will only increase when you don't have to pay someone who isn't riding to operate the vehicle.