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Published byEugene Simpson Modified over 8 years ago
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John Gibb DKS Associates Transportation Solutions
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The Park-and-Ride Problem for Transit Auto Access: Which park-and-ride transit stop for a trip Getting level of service “skim” values for auto and transit legs Assigning auto and transit legs
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Customary Solutions (Trip-Based) Zone-Station links by auto access “shed” Capacity restraint by art, trial and error Drive legs not assigned Intermediate zone EMME triple-index (convolution) Multinomial logit Capacity restraint by shadow-price
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Individual trip modeling - as in activity-based model Heterogeneous choice sets & behavior Time-specific Sub-mode choice Single outcome per choice Determines auto & transit trips in both directions
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“Real world”: Parking available to all until full Time-dependent choice set Arrival time determines individual’s priority (not drive distance or analyst’s judgment) Commuter behavior: Know when lots fill No frustrated arrivals to full lots
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Original Sacramento Application: Chronological Order One-pass algorithm: Sort trips by presumed departure time Choose best-utility among available lots Accumulate parking loads; make unavailable when full
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Limitations of the one-pass method Loss of choices Departure & parking-arrival time varies among alternatives One can leave earlier to beat a lot’s fill-time Improved method for Sacramento update and new Seattle ABM in progress…
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Crawford-Knoer matching algorithm (1981) Generalizes Gale-Shapely (1962) Hospital-residents, college admissions, stable marriage problems Iterative rounds of “proposals” until constraints satisfied. In C-K, rejected proposals are adjusted & resubmitted
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C-K algorithm for parking, briefly Iterative rounds Parking choice Latecomer rejection Rejectees adjust departure time to that lot a unit-step earlier Departure-time adjustment counts against utility Choice may repeat Trip “accepted” may be “bumped” in a later round Stop when no parking oversubscribed
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Crawford-Knoer properties User-optimal equilibrium Escalation of early arrival times Last-minute arrival rush No denial of choice Gradual adjustment avoids problems, can use efficient methods Needs an early-departure utility parameter
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System equilibration flow Skim Matrices Activity-Based Demand Model Trips P&R lot placement Network Assignment Lot-Full Times
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Thanks! Questions, requests for reports welcomed at jag@dksassociates.com DKS Associates TRANSPORTATION SOLUTIONS www.dksassociates.com
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