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Transportation Demand Forecasting *ASSIGNMENT WORKABDUL
RASHEED14011D8115INFRASTRUCTURE
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Transportation PlanningDefinitionScience & StudyUrban,
Regional or National level
Transportation Demand Forecasting4 step process
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Transportation PlanningTypes of plansNetwork Corridor
Project
Plan Duration Short Long
Purpose of plansImplementation/ResearchStrategy Policy
Development*The information needed for decision makers to choose
among alternative strategies for improving transportation system
facilities is provided
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Transportation planning is future-oriented so always there are
Uncertainty in predictions
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Types of Transportation PlansMotivator:
FundingCoordinationSpecific Need
Planning Level:Statewide State Highway PlanSub-Regional Five
Year PlanRegional / Metropolitan Area wideLocalCorridor Plans
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Need for ForecastingTransportation plans which are of long-range
in scope and involving planning of 20-25 yrs ahead.Impacts of
facilities or modes of travel Lines on existing.RoadsLight railBus
service Geometric designPavement design*
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Types of decisionsTime (when do you go?)Destination (where do
you go?)Mode (how do you get there?)Route choice (what route do you
choose?)InfluencesEconomicSocial
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How it Starts*
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This helps in traffic forecast and is carried out using
The conventional approach to transportation forecasting is based
on what is commonly know as the 4 STEP MODEL
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Trip GenerationEstimates the number of trips from given origins
and destinations (Housing / Employment locations)Trip
DistributionDetermines the destination for each trip from a given
originMode ChoiceDetermines the mode choice for each trip various
(SOV, HOV, Bus, Rail, Water)Route AssignmentDetermines the specific
route for each trip
Four step Model
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Trip Generation
Determines the mathematical relationship between no of trips
produced in a zone and land use and socio economics
characteristics
Assumptions:Trip-making is a function of land useTrips are made
for specific purposesDifferent trip types are made at different
times of the dayTravelers have options available to themTrips are
made to minimize inconvenience
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Trip DistributionConnects the trip-ends predicted by the trip
generation models between any set of two zonesDetermined origins
and destinations through estimated trip generation modelsMost
common model in practice is the "gravity model"
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Trip AssignmentProcedure by which route chosen by a trip maker
is determinedAssigns trips to pass through the networkInter zonal
flows are assigned to selected routes
Most common methodAll-or-Nothing assignment(free assignment)
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Models so formulated are calibrated and checked for their
accuracy before they are further utilized for determining future
travel pattern
Transportation forecasting models, with proper accounting for
land use impacts helps in predicting growth pattern for land use
such as industrial, commercial ,recreational and open spaces ZONING
regulations with cost and availability of land etc should be
employed in building such models
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Future land use activity arrangements and informations
concerning to future income levels and family size cars ownerships
rates employment and other economic activitiesThis are provided as
inputs and formulated for future trip generation rates
The output from the above stages yields on each(link of)network
and speed and level of service afforded by the planned facility
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