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to serve abutting land uses. A collector street may also accom- <br />modate public transit such as buses. <br />Subcollector. The subcollector provides passage to access streets <br />and conveys traffic to collectors (Figure 2 -4). Like the access <br />street, the subcollector provides frontage and access to residential <br />lots but also carries some through traffic to lower -order (access) <br />streets. The subcollector is a relatively low - volume street. <br />Access Street. Sometimes called a place or lane, the access street <br />is designed to conduct traffic between dwelling units and higher - <br />order streets (Figure 2 -5). As the lowest -order street in the hier- <br />archy, the access street usually carries no through traffic and in- <br />cludes short streets, cul -de -sacs, and courts. The cul -de -sac, a <br />dead -end street with a turnaround area at the end, is used exten- <br />sively because it provides a quiet, low- traffic environment, elim- <br />inates through traffic, and permits the efficient use of land. While <br />some observers classify residential streets as either collectors or <br />locals, this book further subdivides locals into subcollectors and <br />access streets because of the desirability of distinguishing be- <br />tween the function and needs of these two significantly different <br />street types. Access streets are noteworthy for their complete lack <br />of through traffic and for the fact that they serve only a few dwell- <br />ing units. Subcollectors usually serve more dwellings and carry a <br />small volume of through traffic to one or more access streets. <br />This book, then, is limited to the design characteristics of res- <br />idential collector, subcollector, and access streets. The streets <br />needed to serve other types of uses such as retail, office, or indus- <br />trial development are dramatically different in their operational <br />requirements. <br />Street classes based strictly upon width and type of pavement <br />cross - section are insensitive to varying user requirements. Such <br />a classification system often results in standardized dimensions <br />and designs for residential and collector streets and dictates con- <br />struction in accordance with one or another set of dimensions. <br />This approach can seriously inhibit designs based upon actual <br />need and can force all construction to provide for the most rigorous <br />preconceived conditions, which may or may not occur in practice. <br />In properly designed residential neighborhoods without through <br />traffic, travel distances from residences to collector streets are <br />short, traffic speeds are low, lane capacity and design speed are <br />not controlling design factors, and inconvenience or minor delay <br />is an inconsequential consideration. Further, drivers and residents <br />expect and accept both brief delays and the need to decrease speed. <br />In fact, it is customary for the individual to drive carefully to avoid <br />children and pets. <br />Traffic conditions for most new subdivisions as well as changes <br />in the projected traffic patterns due to the development of sur- <br />Page 7 <br />Design Considerations <br />