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Unformatted text preview: 3. Modal Choice 3. Modal Choice (Modal Split) (Modal Split) driving 14 70 6 10 In a typical travel situation, trip makers can select between several travel modes: These may include: driving riding with someone else taking the bus walking biking etc bus other carpool A modal choice, or modal split, model is concerned with the tripmakers behavior regarding the selection of the travel mode. The reasons underlying this choice vary between individuals, trip type, and the relative level of service and cost associated with the available modes. Each person has established a pattern of modal choice that remains relatively constant as long as other conditions remain the same. When significant changes in these conditions occur, tripmakers respond to varying degrees by shifting from one mode to another. e.g. a significant increase in parking fees may induce some people from driving a car to riding a bus. The characteristics of the trip also have an effect on mode choice. Somebody might prefer using transit to work, but driving his car for social trips. Also, socioeconomic factors: income and age Depending on their position in the demand forecasting sequence, modal choice models are classified either as predistribution (tripend) models or as postdistribution (tripinterchange) models. Trip generation Modal split Transit trip distribution Auto trip distribution Transit trip Auto trip Trip end models Trip generation Trip distribution Transit trips Auto trips Transit trip Auto trip Tripinterchange models Modal split The development of a mode choice model necessitates the use of some consistent theory of travelers decisionmaking process. Of the decisionmaking theories available, one that is based on the microeconomic concept of utility maximization has enjoyed comparatively widespread acceptance in mode choice modeling. The basic assumption is that a traveler will select the mode that provides the most utility in the economic sense. mk kmn n mn mk X b V + = here; V mk = total utility provided by mode alternative m to traveler k b mn = coef. estimated from traveler survey data for mode m corresponding to mode or traveler characteristic n. here; X kmn = traveler or mode characteristics n (e.g. income, travel time mode) for mode m for traveler k. mk = unspecified portion of the utility of mode m for traveler k (randomunlikely that individual travelers utility functions can ever be specified with certainly) For notational convenience, define the specifiable nonrandom portion of the utility as: kmn n mn mk X b U = The probability that a traveler will choose an alternative m, is equal to the probability that alternatives utility is greater than the utility of all other possible alternatives. The probabilistic component arises from the fact that the unspecifiable portion of the utility expression is not known and is assumed to be a random variable....
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This note was uploaded on 01/13/2011 for the course CECS Transporta taught by Professor Essamradwan during the Spring '10 term at University of Central Florida.
 Spring '10
 EssamRadwan

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