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Transportation Planning

Transportation Planning. What is a Traffic Model?. Typical Definition: A computer program that runs mathematical equations using input data to replicate travel choices that individuals make The output is a measure of future travel demand that is expressed in terms of future traffic volumes.

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Transportation Planning

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  1. Transportation Planning

  2. What is a Traffic Model? • Typical Definition: • A computer program that runs mathematical equations using input data to replicate travel choices that individuals make • The output is a measure of future travel demand that is expressed in terms of future traffic volumes. • Simply: A forecast of future travel • Where are people traveling to and from • What routes are they choosing to get there

  3. Why are Models Important? • Models are the heart of Transportation Planning • They help us determine how much traffic will be on our roadways in the future • They help us to understand the impact that development has on our transportation system • They guide future investment strategies • Models allow us to make informed decisions.

  4. What Are Travel Models Used For? • Provide the best possible information about future needs • Determining where congestion may be in the future • Determining what projects will alleviate or minimize that congestion. • Scenario analyses (What ifs) • How many lanes are we going to need? • Determine traffic impact due to land use changes

  5. Example Scenario • Planner or Engineer • Finite $ in available funding • Your job: ID what roadway projects will be in the MPO Transportation Improvement Program • Resources are scarce • Choices need to be good ones • Public drives the roads every day and are ready to complain • How do you go about selecting solutions? • Use the travel demand model to aid in determining how to address existing congestion problems. • Test various projects to determine effectiveness • Measure in VMT and VHT savings

  6. Travel Demand • Why did the chicken cross the road? • Duh -- to get where they want to be???

  7. Why Do People Travel? • Hence, the truism that “Travel is a derived demand” -- i.e. the demand for travel is derived from the demand for spatially-separated activities • Corollary: Travel is a disutility, that people try to minimize

  8. Travel… • Saved travel time is a benefit, hence a basis for valuing transportation improvements • THE largest benefit component in most cost-benefit analyses • We can reduce travel by… • ... making it more expensive • congestion pricing, fuel taxes, parking pricing

  9. Travel… • We can reduce travel by… • … bringing activities closer together • increasing density and mixture of land uses • … using ICT (information and communication technology) to conduct the activity remotely • telecommuting, -conferencing, -shopping, -education, -medicine, -justice

  10. But is that the only reason people travel -- to get somewhere in particular?

  11. Why Would Travel be Desirable? • Escape • Exercise, physical/mental therapy • Curiosity, variety-, adventure-seeking; conquest • Sensation of speed or even just movement • Exposure to the environment, information • Enjoyment of a route, not just a destination • Symbolic value (status, independence) • Buffer between activities, synergy with multiple activities

  12. Trends In Travel Demand

  13. Global Changes, 1960-1990 NAM: N. America LAM: Latin America WEU: W. Europe EEU: E. Europe FSU: Former Soviet Union MEA: Middle East and North Africa AFR: Sub-Saharan Africa CPA: Centrally Planned Asia and China SAS: South Asia PAS: Other Pacific Asia PAO: Other Pacific OECD Motorized mobility (pkm) per capita, 1960 and 1990. Source: Schafer, 1998

  14. Avg. Annual Growth Rate of Cars and Their Use, 1970-90

  15. Mobility as a Function of GDP NAM: N. America LAM: Latin America WEU: W. Europe EEU: E. Europe FSU: Former Soviet Union MEA: Middle East and North Africa AFR: Sub-Saharan Africa CPA: Centrally Planned Asia and China SAS: South Asia PAS: Other Pacific Asia PAO: Other Pacific OECD Motorized mobility (car, bus, rail, and aircraft) per capita by world region vs GDP per capita, between 1960 and 1990. Source: Schafer, 1998

  16. Car Ownership vs. GDP SAS: South Asia PAS: Other Pacific Asia CPA: Centrally Planned Asia and China Estimated motorization rates for CPA, PAS and SAS, compared with the observed rise in motorization in several countries. Source of historical data: United Nations, 1960; United Nations, 1993a and IRF, various years. Source for figure: Schafer and Victor, 2000

  17. Projected Mobility, 2050 Historical and estimated future total global mobility by mode in 1960, 1990, 2020 and 2050. Source: Schafer and Victor, 2000

  18. Survey Data Land Use Step 1: Trip Generation TransportationNetwork Step 2: Trip Distribution Step 3: Mode Choice Step 4: Trip/ Traffic Assignment The 4 step transport planning process • OUTPUT • Estimated trips • Estimated modal shares • Estimated travel speeds • Estimated travel delays • Air Quality

  19. Inputs- Demographic Data • Household size • Income level • Autos per household • Age

  20. Inputs- Transportation Systems • Most streets, all highways • Parking • Public Transportation • Speeds, travel times, and speed limits • Traffic volumes • Transit ridership and fares • Vehicle occupancy

  21. Inputs- Land Use • Current land use and zoning • Activity for each area • Land use and zoning plans • Base maps and topography

  22. Land Use • Definition: Spatial pattern of different economic uses of land • Residential • Industrial • Commercial • Institutional • A component of the urban system • Defines, at least in part, the personality of a city

  23. Urban form: spatial arrangement of built environment elements and urban activities Density Homogeneity Concentricity Connectivity Land Use

  24. Changes in location, type and density of land use affects travel choices and patterns Past transportation decisions evident in today’s development patterns Transportation-Land Use Connection

  25. Transportation-Land Use Connection Land Use Trips Land Value Transportation Needs Accessibility Transportation Facility

  26. Accessibility • Ease of movement between places • Can be assessed separately for different modes, purposes, etc.

  27. Sprawl is random unplanned growth characterized by inadequate accessibility to essential land uses such as housing, jobs, and public services, i.e., schools, parks, and mass transit Urban Sprawl

  28. Urban Sprawl • Sprawl is directly identified with urban growth- as cities get bigger, they expand around their peripheries • Big cities are attracting population.. But population is being added to the edge at lower densities and the dominant transport is the car, for ease of access • Population and other activity is also decentralizing very fast to lower density suburbs

  29. Results of Sprawl • More Vehicle Miles Traveled (VMT) • Longer Travel Times • Greater Number of Auto Trips • Less Cost-Effective and Efficient Transit

  30. Building a Travel Demand Model DATA • Population (how many people do we have?) • Households (where do they live) • Employment (jobs, shopping, restaurants, recreation, etc.) • Schools and college locations • Roadway Network – TAZ (traffic analysis zones)

  31. Traffic Analysis Zones (TAZ) • Used to represent transportation demand • Design guidelines • equal size • homogeneous land use (residential, retail, industrial, etc) • not crossed by network or physical barriers • Trip assumed to originate from a single point (centroid)

  32. TAZ Characteristics • TAZ boundaries are major roadways or physical barriers such as railroads, rivers, airport boundaries etc. • Typically follow block or block group boundaries • Goal: replicate areas of Origin and Destination for trips being made. • Home to Work ; Home to Shopping ; Work to Shopping, etc

  33. TAZ Characteristics • Zones are characterized by their population, employment, and other factors • They are the places where trip making decisions are made (trip producer) and the trip need is met (trip attractor)

  34. Traffic Analysis Zones

  35. TAZ Characteristics cont’d • Simple representation of the geometry of the transportation systems (usually major roads or transportation routes) • Links: sections of roadway (or railway) • Nodes: intersection of 2+ links • Centroids: center of TAZs –Trip making is assumed to begin at the zone centroid • Centroid connectors: centroid to roadway network where trips load onto the network

  36. Trip generation Potential Trip Generation • Decision to travel for a specific purpose (e.g. eat lunch) -HOW MANY TRIPS??

  37. Trip Generation • Defines the relationship between trip-making, socio-economic characteristics, and land use activities • Purpose • Predict how many trips will be made • Predict exactly when a trip will be made

  38. Trip Purposes

  39. Trip Generation • Methods • Cross Classification • Regression Analysis –Linear relationship

  40. Cross-Classification • Households in TAZs aggregated into groups • Rates for each group used to determine the number of trips. • Trip rates based on household characteristics (income level, vehicle ownership, household size, … )

  41. Cross-Classification Method (cross-classification rates)

  42. Regression Analysis • Allows multiple variables and nonlinearity • The number of trips = f (population, autos, number of dwelling units, …) • The trip predictors (population, autos, … ) need to be independent

  43. Trip distribution Travel demand Trip Distribution • Choice of destination (a particular restaurant? The nearest restaurant?) -Given a location, where do people go to satisfy demand for an activity type? -Determine origin and destination of trips

  44. Trip Distribution

  45. Gravity Model

  46. Trip Distribution-Gravity Model

  47. Trip Distribution • f(D) –travel impedance can be a function of distance, time, or user cost. Usually use time.

  48. Trip Distribution

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