Human Transport

For human transport, the relationship between time space and distance is fixed: S=D/T. Travel time can be reduced by increasing speeds, but total energy output remains a limiting factor; and higher speeds are less efficient. Prior to the advent of vehicular transit, travel speed was nearly constant. With speed constant, it is only possible to increase the distance of residence from work by increasing the amount of travel time. With wage labor, the combination of hours worked and necessary hours for rest provided a hard limit on the amount of travel time available. Thus, any efforts to de-congest a city (to lower overall activity density) are reliant on vehicular transportation, for which travel speed is not constant. (Vehicular transportation also provides a limited conversion of travel time in resting time). The adoption of mass transit in urban places did not initially occur to limitations in space (as is currently the case), but rather due to limitations on total human energy output. The 'massification' of transportation is more efficient than individual transportation. It also facilitated the replacement of human bio-energy with that from fossil fuels. 

Housing and transportation cost trade-offs

History is demonstrably replete with examples where housing has been allowed to depreciate into dangerous and barely habitable conditions while still remaining attractive to prospective tenants. Many of the health and safety initiatives of the urban Progressives was dedicated to overcoming the economic rationality of this behavior. However, in some cases, the remedy has proven worse than the disease.....