When we talk about access as a value that should guide transport policy, we need to address access for whom, not just access to where by what mode. In the auto-dependent US, the mode that offers the most access in most places currently is the car. Yet cars are expensive, and many people struggle with basic access (and mobility) simply because they can’t afford it. Transport is the second largest spending category for US households, behind only housing. This is the case even as transport is heavily subsidized, regardless of mode.1 As discussed in Subsidy,2 the general approach is to spread whatever help is offered thinly across infrastructure capital investment. This does little to help those with the least.
Should government subsidize transport? If government subsidizes transport, should it subsidize producers or consumers? If a government gave money to consumers, they could spend it on what they want, paying for a service, which if it covers operating costs, could lead to more investment. If it gave money directly to producers, they spend it on more supply. Which leads to a better outcome?
Xie, Feng and David Levinson (2008) The Weakest Link: A model of the decline of surface transportation networks. Transportation Research part E 44(1) 100-113. [doi]
This study explores the economic mechanisms behind the decline of a surface transportation network, based on the assumption that the decline phase is a spontaneous process driven by decentralized decisions of individual travelers and privatized links. A simulation model is developed with a degeneration process by which the weakest link is removed iteratively from the network. Experiments reveal how the economic efficiency of a network evolves during the degeneration process and suggest an “optimal” degenerated network could be derived during the decline phase in terms of maximizing total social welfare.
Keywords: Decline; Transportation network; Simulation; Welfare; Accessibility