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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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Sequential Demand Forecasting Models

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travel behavior
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
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
trip generation4
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
trip purpose
Trip purpose
  • work, school, shopping, social, recreational
  • Can be single purpose or multi purpose
zonal model
Zonal model
  • look at trips between zones
  • A zone is a homogeneous area of
    • land use
    • population
    • income
    • vehicle ownership
    • same access paths
trip rate analysis
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?
pass by trips
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)
linked trips
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
  • 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
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
grand vista12
Grand Vista
  • Spreadsheet
trip distribution
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
trip distribution14
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
trip distribution15
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
trip distribution16
Trip Distribution
  • Attraction depends on
    • uniqueness
    • distance
    • closeness to other services
    • urban or rural
  • Shopping Centers usually have a 5 mile radius of influence
grand vista17
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
modal choice
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
  • Diversion curves
    • based on auto costs, transit travel time, auto travel time, transit LOS, auto LOS, income
  • Utility and Disutility
  • measures satisfaction or impedance of choice
  • All provide a percentage of trips per mode
    • As inputs change, outputs also change
network assignment
Network Assignment
  • Determine path
  • Number of paths depends on network
  • person trips vs vehicle trips
  • Transit Assignment
    • depends on capacity, facilities, connectivity
network assignment22
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
link flow
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”
minimum path algorithms
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
minimum path algorithms25
Minimum Path Algorithms
  • All or Nothing
  • Multipath Traffic Assignment
  • Capacity Restrained
  • Transit Assignment
all or nothing
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
grand vista27
Grand Vista
  • Add traffic to links to get build volumes
  • Spreadsheet