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PAGINA 149
II. URBAN STREETS
In the hierarchy of street transportation facilities, urban streets (including arterials and collectors) are ranked between local streets and multilane suburban and rural highways. The difference is determined principally by street function, control conditions. and the character and intensity of roadside development. Arterial streets are roads that primarily servelonger through trips. However, providing access to abutting commercial and residential land uses is also an important function of arterials. Collector streets provide both land access and traffic circulation within residential, commercial, and industrial areas. Their access function is more important than that of arterials, and unlike arterials their operation is not always dominated by trafficsignals. Downtown streets are signalized facilities that often resemble arterials. They not only move through traffic but also provide access to local businesses for passenger cars, transit buses, and trucks. Turning movements at downtown intersections are often greater than 20 percent of total traffic volume because downtown flow typically involves a substantial amount of circulatory traffic.Pedestrian conflicts and lane obstructions created by stopping or standing taxicabs, buses, trucks, and parking vehicles that cause turbulence in the traffic flow are typical of downtown streets. Downtown street function may change with the time of day; some downtown streets are converted to arterial-type operation during peak traffic hours. Multilane suburban and rural highways differ from urbanstreets in the following ways: roadside development is not as intense, density of traffic access points is not as high, and signalized intersections are more than 3.0 km apart. These conditions result in a smaller number of traffic conflicts, smoother flow, and dissipation of the platoon structure associated with traffic flow on an arterial or collector with traffic signals. The urban streetsmethodology described in this chapter and in Chapter 15 can be used to assess the mobility function of the urban street. The degree of mobility provided is assessed in terms of travel speed for the through-traffic stream. A street's access function is not assessed by this methodology. The level of access provided by a street should also be considered in evaluating its performance, especially if the streetis intended to provide such access. Oftentimes, factors that favor mobility reflect minimal levels of access and vice versa.
II . URBANAS CALLES
En la jerarquía de las instalaciones de transporte de la calle, las calles urbanas (incluidas las arterias y colectores ) se clasifican entre las calles locales y carreteras suburbanas y rurales de varios carriles . La diferencia está determinadaprincipalmente por la función de la calle, las condiciones de control . y el carácter y la intensidad del desarrollo en carretera . Calles arteriales son las carreteras que sirven principalmente ya través de los viajes. Sin embargo, proporcionar acceso a los usos de la tierra colindante comerciales y residenciales es también una función importante de arterias . Calles colectoras proporcionan tantoacceso a la tierra y la circulación del tráfico en las áreas residenciales , comerciales e industriales . Su función de acceso es más importante que la de arterias , y a diferencia de los arteriales su funcionamiento no siempre está dominado por las señales de tráfico . Las calles del centro están señalizadas las instalaciones que a menudo se asemejan a los arteriales . Ellos no sólo se mueven através del tráfico, pero también proporcionan acceso a los negocios locales para turismos, autobuses de transporte y camiones. Movimientos de giro en las intersecciones del centro son a menudo mayor que 20 por ciento del volumen total de tráfico porque el flujo de la ciudad normalmente implica una cantidad considerable de tráfico circulatorio. Conflictos peatonales y carriles obstrucciones creadas...