Transportation Systems
Source: Urban Transportation Systems CHAPTER1 Overview—Criteria for Selecting Modes Life in cities—i.e., in organized human settlements, which are mostly referred to as communities in this book—is possible only if people have mobility1 on a daily basis—the ability to move around so that they can do what they have to do or like to do. One char- acterization of a city is that it consists of specialized, frequently clustered, activities that perform discrete functions. Residences are separate from workplaces, major shopping is concentrated in identifiable centers, and larger entertainment and relaxation facil- ities are found at specific locations. They have to have accessi- bility.2 Unlike in a village, very few of these destinations are reachable on foot; at least, they tend not to be within a convenient walking distance. The large ancient and medieval cities were actually conglomer- ations of neighborhoods in which daily life could take place 1 Mobility is here defined as the ability of any person to move between points in a community by private or public means of transportation. The usual obstacles to mobility are long distances, bad weather, steep hills (all constituting friction of space), but, above all, the unavailability of services, high fares, and possibly other forms of exclusion. 2 Accessibility is here defined as the possibility of reaching any activity, estab- lishment, or land use in a community by people (or by conveyances of goods or information) who have a reason to get there. It is a measure of the quality and operational effectiveness of a community. 1 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies.
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