Accessibility can be defined as the number of opportunities available within a given distance (p. 4), that is to say the ability to reach certain necessities, i.e. work, school, stores within a certain proximity. Whereas mobility is the ability to move from one activity area to the other ( p.4). these two concepts are intertwined. Before the advancements of transportation, mobility was based on a person's individual walkable sphere, or that of a horse. With the introduction of even the most basic steam powered vehicle and the rails on which it ran, accessibility greatly increased and thus the ability of the individual to quickly access more opportunities also increased. However steam-powered vehicles were greatly dependent on where the tracks lay, that is to say a town the tracks ran through suddenly greatly increased in accessibility and thus it became far more likely for an individual to stop there, (because of the ease of mobility) in the same regard a town hundreds of miles away from the nearest track, kept its original inaccessibility and thus the individual who lived there had their mobility restrained, not only was the chances of growth limited, but many towns that were far from the tracks were abandoned.
The invention of the automobile was the greatest advancement to mobility achieved, because the car would allow the indiviual driving to determine their own exact destination, with this new advancement, the accessibility of certain areas greatly increased, with new roads leading out of the cities built after the Second World War, people began to locate along the outskirts of the city where land was cheaper and thus larger. The suburbs were born, and along with the suburbs came the structure to support them, just like with the advancement of trains, the land-use along the track changed and bloomed to accommodate the travelers, i.e. gas stations, stores, schools and eventually jobs were relocated along the routes and the newly developed suburbs. The concept can be applied today, as mobility (i.e. speed limits and new road and freeway construction) changes to accommodate the increasing number of vehicles on the road so does the accessibility to the opportunities that lie on that path. In the same regard, as traffic patterns alter, and the speed (mobility) decreases the individual desire to travel long distances to reach opportunities that lie further away demises.
However the change in mobility can be said to have long lasting effects. New road construction or speed limit changes, will lead people to make use of the new found opportunity to travel faster and thus traffic will follow the change. along the developed route, the demand of better land-use will follow, starting at first with simple suburbanization, and slowly leading to a more concentrated form of development or further sprawl.
Hanson, Susan (ed.). 1995. The Geography of Urban Transportation. New York, New York: The Guilford Press