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DRAFT November 21, 1995 trips were distributed to other external zones and TAZs, respectively, by • percentages according to the "draw", or total trip generation within each zone. The remaining TAZ trip ends after distribution of E-I trips were categorized and I-I. I-I trips were classified as either productions or attractions such that the total of productions from all TAZs was equal to the total of attractions. All residential trips generated were called productions, and each was assumed to be attracted to a commercial/industrial/ recreational generator. Remaining commercial/industrial/recreational trips were divided evenly between productions and attractions. Trip distribution takes the form of a matrix, or a trip table. For Elk River, a trip table was created for each category of trip: E-E, E-I, and I-I. Tables 3A, 3B, and 3C are the trip tables for replication of the existing transportation system; Tables 3D, 3E, and 3F are for the ultimate forecast. 3. Network Assignments After trips are distributed they must be assigned travel paths on a network. A network is a series of links and modes, where links represent roadway segments and nodes represent either intersections or network loading • points. Each link has a travel time, a function of its length and travel speed. Loading links are links used to place trips generated in TAZs onto the network. Each TAZ may have one or several loading links. Trips are assigned to the network generally following the path of least travel time between the origin and destination zones. Several methods for assigning trips onto a network are available. Capacity restraint analysis is an iterative process whereby trips are assigned, the network is check for links whose assigned volumes exceed link capacity, travel times are adjusted upward onover-capacitylinks, and trips are re-assigned. The steps are reiterated until the network is balanced. This method shows how the network will be loaded after drivers adjust their travel behavior to compensate for congested areas, but it does not show how the network is loaded if every driver can take the most desired route. All-or-nothing analysis, on the other hand, assigns every trip to its most desired path without considering segment capacities. Since the purpose of the Elk River Transportation Plan was to identify areas where congestion could be anticipated in the future and provide solutions for these problem areas so that the number of drivers forced by congestion onto alternate routes could be minimized, we decided that an all-or-nothing analysis would be the most useful. It permits the planner to see where drivers want • to travel, and to make changes to the system that encourage the driver to use that route. If more drivers can use their first choice routes through the CTP-230.156 -7- 230-156-80