trans_sys_chap25

trans_sys_chap25 - Introduction to Transportation Systems 1...

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Introduction to Transportation Systems 1
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PART III: TRAVELER TRANSPORTATION 2
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Chapter 25: The Urban Transportation Planning Process and Real-Time Network Control 3
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Networks ± We are interested in network behavior -- how the network as a whole behaves -- which involves going from choices that individual people make about transportation to understanding how the network in its entirety operates. ± What are the flows on the network? ± What are the levels-of-service being provided? ± How much capacity is needed at various links and nodes? ± What might be done to enhance the network? ± How can we control the network in real-time? ± We need to aggregate predicted individual choices to overall network flows and performance. 4
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The Urban Transportation Planning Process ± We begin the process by building a network. ± In performing this kind of analysis, we take a set of geographical areas, and aggregate them into what are called “zones”. ± For each zone, we define a node or centroid, often at the population center or major activity center of the zone. ± A network is constructed by connecting the nodes with links. 5
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Constructing a Network from Zones Node 5 Node 1 Zone 5 Zone 1 Figure 25.1 6
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± On this network, we overlay the transportation network which is usually multimodal including, say, highway (both auto and bus) and rail transit. 7
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Nodes as Zone Centroids and “Dummies” Figure 25.2 8
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Choosing the Number and Size of Zones ± There is a fundamental modeling trade- off here. We can choose a relatively small number of large-area heterogeneous zones, which makes network analysis easy because with a small number of zones, the network is
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This note was uploaded on 12/06/2011 for the course ESD 1.221j taught by Professor Josephsussman during the Fall '04 term at MIT.

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trans_sys_chap25 - Introduction to Transportation Systems 1...

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