Sequential demand forecasting models
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Sequential Demand Forecasting Models CTC-340 Travel Behavior 1. Decision to travel for a given purpose People don’t travel without reason 2. The choice of destination 3. The choice of mode 4. The choice of route or path Trip generation

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Travel behavior l.jpg
Travel Behavior

  • 1. Decision to travel for a given purpose

    • People don’t travel without reason

  • 2. The choice of destination

  • 3. The choice of mode

  • 4. The choice of route or path


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Trip generation

  • Forecast the number of trips which begin or end in a Traffic Analysis Zone

    • Must be calibrated

    • Dependent upon

      • land use

      • socioeconomic factors

      • at both ends


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Trip Generation

  • Trip ends (Q)

    • How many trips are being made due to a land use

  • Production (P)

    • origin of residential based trip

      • Home - based trip -- begins or ends at home

      • non-home based trip -- trip does not begin or end at home

  • Attraction (A)

    • destination of residential based trip


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Trip purpose

  • work, school, shopping, social, recreational

  • Can be single purpose or multi purpose


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Zonal model

  • look at trips between zones

  • A zone is a homogeneous area of

    • land use

    • population

    • income

    • vehicle ownership

    • same access paths


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Trip Rate Analysis

  • Determine the average productions and attractions of a trip generator

  • ITE Trip Generation Handbook

    • rates by land use

    • based on 1000 sf, employees, students, dwelling units, etc

  • Need to determine whether the generator or the adjacent street controls volumes generated

    • Why?


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Pass-by trips

  • Trips not generated by land use

    • Vehicle deviates from its course to use land use and then continues on its path

    • What are major land uses where this type of trip is important

    • can be 25 - 60% of trips

    • Subtract trips from through traffic, add to turning traffic (in and out)


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Linked Trips

  • Trips with multiple destinations all within one area and not requiring road access between destinations

  • 10 - 20 % of trips for certain land uses

    • Used in Malls and shopping centers


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Example

  • Drive in Bank 5,000 sf w/drive thru

  • 60,000 sf office building

  • AM & PM trips

  • What other times might be important?


Grand vista l.jpg

131 Single Family Homes

370 Townhouse units

400 Garden Apartments

640K Office Park

257K Shopping center

3 banks & Restaurants

365K Industrial Park

90K Medical Office

180 Room Hotel

Grand Vista


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Grand Vista

  • Spreadsheet


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Trip Distribution

  • Where do the trips come from?

  • Gravity Model provides answers

    • force of attraction between two bodies is proportional to the product of their masses and inversely proportional to the product of the distance between them


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Trip Distribution

  • F is the friction factor

  • proportional to W

    • F = 1/W^2

  • P is productions in i

  • A is attractions in j

  • Q is the trips from i to j

  • K is the difference in socio-economic factors from i to j


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Trip Distribution

  • Gravity model works for large and small developments

    • may need to calibrate large developments

  • usually use census tracts as zones

  • can use information developed by developer

  • Retail stores use zip codes


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Trip Distribution

  • Attraction depends on

    • uniqueness

    • distance

    • closeness to other services

    • urban or rural

  • Shopping Centers usually have a 5 mile radius of influence


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Grand Vista

  • 6 access roads

  • Need to distribute traffic to each site driveway

    • Based on destination/start point

    • This is where judgment comes in

  • Spreadsheet


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Modal Choice

  • Trip makers choose mode

    • trip type is a factor

    • socio-economic status is a factor

    • transit captives

  • 2 types of models

    • pre-distribution - attraction has no impact on mode

    • Post-distribution – attraction does impact mode


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Models

  • Diversion curves

    • based on auto costs, transit travel time, auto travel time, transit LOS, auto LOS, income


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Models

  • Utility and Disutility

  • measures satisfaction or impedance of choice

  • All provide a percentage of trips per mode

    • As inputs change, outputs also change


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Network Assignment

  • Determine path

  • Number of paths depends on network

  • person trips vs vehicle trips

  • Transit Assignment

    • depends on capacity, facilities, connectivity


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Network Assignment

  • 3 major times - Peak Hours

  • Trip direction is important

  • Diversion Curves

    • good when only two paths to choose from

    • arterial vs freeway

    • many iterations

      • based on travel time of each facility


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Link Flow

  • Flow that occurs on a link in a network

  • Route Choice Behavior

    • user equilibrium

      • goes on shortest path

    • system equilibrium

      • cost of system is minimized

    • stochastic equilibrium

      • user assigns self to “shortest path”


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Minimum Path Algorithms

  • Minimizes most important user criteria

    • cost, time, distance

    • can also develop trade-offs between criteria to determine “best route”

    • can determine the traffic on a link


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Minimum Path Algorithms

  • All or Nothing

  • Multipath Traffic Assignment

  • Capacity Restrained

  • Transit Assignment


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All or Nothing

  • Need to find minimum path tree for network

  • place traffic on links

  • gives info on most heavily used links

  • not accurate for high volumes


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Grand Vista

  • Add traffic to links to get build volumes

  • Spreadsheet





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