The social and physical geography of the nation's cities has been radically transformed over the 125 some-odd year history of the automobile. This is especially true in the past 50 years as rural populations have become concentrated into urban and suburban populations. The automobile enabled people to disengage aspects of their daily lives from proximity to those activities which has concomitant effects upon how people value distance, time and, especially, the allocation of their financial resources. Indeed, having and using an automobile is effectively a requirement for modern life in most places.
As a result of this shift, people are now beholden to swings in the commodity cost of fuel as well as the constrained availability of shared resources in densely populated areas such as road capacity and parking. Urban governments have, to varying degrees, responded to the pressures on shared resources by increasing the reach and modes of public transportation. Public transportation affords those who reside close to such means of conveyance the ability to shift their personal resources from that of auto fuel, parking, and maintenance to transportation fares, often with the latter at a much lower cost than the former. In areas with such modal fluidity it could be reasoned that increases in the effective costs of one side of the transportation equation will result in defections to the other side.
The city and environs of Seattle meets the fluidity criteria. The region is well developed with roads and highways that are constrained by the natural terrain of the area and no longer have room to expand. This situation results in increased traffic congestion and travel times and is a prime motivation for transit development across the region. Both King County and the Puget Sound region (via Sound Transit) are connected by a public bus network, van pools, rapid transit buses, and in the latter case, commuter and light rail. In fact, the light rail system is currently growing, with the promise of connecting most of the South Sound population centers. Additionally, Seattle has a number of dedicated bike paths and lanes that make bike commuting feasible for those within the city limits, particularly those beyond reasonable walking range of the city center.
This analysis looks at the interaction of gasoline fuel prices, road transportation, and alternative & public transportation available in and near Seattle. It is theorized that increases in fuel prices will result in lower automobile usage as measured by traffic with a related increase in public transportation usage. The results of our analysis, however, are mixed and do not show such a definite effect.
The results are presented in Markdown format with analysis and plot generation code contained in R scripts.