transportation planning, transportation demand analysis land use-transportation interaction...
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Transportation Planning, Transportation Demand Analysis Land Use-Transportation InteractionTransportation Planning FrameworkTransportation Demand Analysis
Land Use-Transportation Interaction
Change inLand use Change in Trip generationChange in travel needs Change in transportation supply (added services & facilities)AccessibilityLand ValuesTransportationserves land usesTransportation shapes land uses
Land Use-Transportation-Environment Interaction Land use Transport Environment.. ZonesUrban AreaChange in land use over time (i.e. change in residential units, commercial land use, industrial land use, retail land use, etc.
Land Use Patterns, Bid RentPressure for growth Demand for land Bid rent Land use pattern Location of activities CBDBid rent $/sq.kmPopulationJobsDistance from CBDCBDDistance
Purpose of Land Use ModelsTo explain/predict:Change in land use as a function of:- accessibility to employment- land value- percent of urban level available vacant land in a zone- public transit accessibility- quality of water & sewer services- etc..
Modelling Travel DecisionsUser Decisions1. To travel (for a given trip purpose at a given time)? (Trip generation)2. Destination? (Trip distribution)3. Mode? (Modal Choice)4. Route? (Assignment of trip to network)Modelling ApproachesFour-stage urban transportation modelling system (UTMS)Unified approaches
Urban Transportation Demand Modelling: Four- Stage Modeling System
Population & Employment ForecastsTrip GenerationTrip DistributionModal SplitTrip AssignmentLink & O-D Flows, Times, Costs, Etc.TransportationNetwork & ServiceAttributes
Four Stages of Urban Travel Demand ModellingIJTrip GenerationOiDjIJTrip Distribution TijJIJMode SplitTij,autoTij, transitIJTraffic assignmentPath of flow Tij,auto through the auto network
Multiple Trip Purposes HW HS NWSGeneration Generation GenerationDistribution Distribution DistributionModal Split Modal Split Modal Split
Road Assignment Transit Assignment
Population EmploymentTrip Rates, etc.TransportNetwork Link & O-D volumes, times, costs, v/c ratios, etc.
The Traffic Prediction Process Trip generation P & A Transit network Road network Trip distribution Modal split Transit person trips Auto person tripsOccupancy Occupancy Transit vehicle trips Auto vehicle trips Freight & other vehicles
Transit traffic assignment Road traffic assignment
Trip GenerationModelling MethodsLinear regression methodCross-classification (category analysis) method/trip rate method_______________________________________________________Trip generationProductions & AttractionsHome-based & non-home based trips
Trip Productions & AttractionsPi = Trip productions of zone i = f(land use, socio-economic characteristics of zone i)Aj = Attractions of zone j = f(land use, socio-economic characteristics of zone j)Regression Model Examples: (P.M. Peak Period Work Trips)Pi = 0.4572 emp - 138 (R2 = 0.87)Aj = 0.1848 pop + 9 (R2 = 0.90)Where emp is total employment pop is total population
Trip Productions & Attractions (Continued)Regression Model Examples: (P.M. Peak Period Non-work trips)Pi = 0.1346pop+0.2897emp+0.0043GLA (R2 = 0.76)Aj = 0.0888emp+ 0.6204DWEL+0.0045GLA+221 (R2 = 0.80)Where emp: is total employment pop: is total population GLA: shopping centre gross leasable area (ft2) DWEL: Dwelling units
Trip Productions & Attractions (Continued)RegressionModel DevelopmentData RequiredZone Pi* Aj* pop emp GLA DWEL1 . . . . . ..2 . . . . . ..._____________________________________________* from O-D surveyData on other variables obtained from city data base
Trip Productions & Attractions (Continued)RegressionModel Development (Continued):Check on :- Partial correlation coefficient (r) . Should be high between P (the dependent variable) & other variables (the independent variables) & Should be high between A (the dependent variable) & other variables (the independent variables) . Should be low between pop, emp, GLA, DWEL (I.e. between independent variables) - Other statistical measures (t statistic for each independent variable)
Trip Productions & Attractions (Continued)RegressionModel Development (Continued):Check on :- R Multiple correlation coefficient (max. value of 1.0)- R2 Coefficient of multiple determination (max. value of 1.0)- Standard Error of Estimate (for the dependent variable - e.g. for Pi)Its value can be checked against the estimated values of the dependent variable.Example: A range of Pi values: 1,000-5,000; St. Error of 100 (very low!)
Trip Productions & Attractions (Continued)Trip Generation Rates (Cross Classification Approach) Trip Production: Step 1
Family Size Auto Ownership 0 1 2 or more1 Trips/household/day234 or more
Trip Productions & Attractions (Continued)Trip Generation Rates (Cross Classification Approach) Trip Production: Step 2Trip productions for Zone i = (Trips/household/day) x (No. of households of that classification).Trips/household/day: is based on O-D surveyNo of households of a given classification: to be forecasted.
Trip Distribution ModelsMany models; most common is gravity model
Zone i PiZone jAjZone j Aj Zone j Aj Tij
Trip Distribution ModelsOrigin-Constrained Gravity Model
Tij = Pi [ Aj Fij Kij for j(Aj Fij Kij) ]WhereTij = Trips produced in zone I and attracted to zone jPi = Trips produced by zone iAj = Trips attracted to zone jFij = Impedance of travel from zone I to zone j (a travel time factor -- expressing an area-wide effect of distance)Kij = A zone-to -zone adjustment factor
Trip Distribution ModelsDestination-Constrained Gravity Model
Tij = Aj [ Pi Fij Kij for i(Pi Fij Kij) ]WhereTij = Trips produced in zone I and attracted to zone jPi = Trips produced by zone iAj = Trips attracted to zone jFij = Impedance of travel from zone I to zone j (a travel time factor -- expressing an area-wide effect of distance)Kij = A zone-to -zone adjustment factor
Gravity ModelThe Fij is usually a some function of the travel time or generalized cost of travel between zones
Fij = C- ij or Fij = t- ij Fijtij or Cij Where is the calibration constantFij = Travel time factor C ij = Generalized cost function t ij = Travel time Kij = A zone-to-zone adjustment factor (takes into account special characteristics of ij combinationsZone 1Zone 2River Example
Pi = for j Tij
Aj = for i Tij
Gravity ModelExampleUsing a gravity model with an impedance term of the form C- , estimate the number of of trips from zone 1 to all other zones. = 1.80. Other inputs are shown below.
Zone Travel time to zone 1 (min) Productions Attractions 1 -- 5000 1000 2 10 2000 40003 20 4000 50004 15 3000 4000__________________________________________________
Gravity ModelHere, Pi for i = zone 1 are to be distributed to other zones by using the gravity model. Assume all K = 1For = 1.80 and given travel times Cij,, and Aj, we find:______________________________________________Zone Aj Cij C- AjC- ij Tij 1 1000 -- -- -- -- 2 4000 10 1/63.1 63.40 2716* 3 5000 20 1/219.7 22.76 975 4 4000 15 1/130.91 30.56 1309 Sum 116.72 5000* T from 1 to 2= 5000(63.40/116.72) = 2716
Gravity ModelFollowing iteration 1 of finding Tij from every zone to all zones, check to see if Ajs match the known values
If yes, the trip distribution problem is solved.
If not, the Ajs have to be adjusted.
The adjustment process is an iterative one (not covered here)