The urban transportation technology of the 19th century is incorporated in four assumptions underlying the monocentric model(O'Sullivan, 2003. Ch. 8): * Central export node (i.e. railroad terminal) * Clean Streets (ie. no trash on streets) * Hub and spoke streetcar system * Agglomeration economies This model also assumes: nothing except commuting cost varies. In reality this is not the case. There are variations in public goods, facilities, environmental quality, taxes, and amenities(O'Sullivan, 2003. Ch. 8).