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FDOT Systems Planning White Paper

FDOT Systems Planning White Paper. Transportation leadership you can trust. A Recommended Approach to Delineating Traffic Analysis Zones in Florida. Presentation Overview. Purpose and Need Reviewers Recommendation Checklist Delineating TAZs in the Base-Year Model

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FDOT Systems Planning White Paper

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  1. FDOT Systems PlanningWhite Paper Transportation leadership you can trust. A Recommended Approach to DelineatingTraffic Analysis Zones in Florida

  2. Presentation Overview • Purpose and Need • Reviewers • Recommendation Checklist • Delineating TAZs in the Base-Year Model • Future-Year TAZ Considerations • Splitting TAZs • Topics Requiring Further Research • Where to Find the Paper • Discussion

  3. Purpose and Need • Purpose • Provide modelers within Florida detailed guidance on a recommended approach to delineating TAZs • Applicable to new travel demand models, or to further refine existing travel demand models • Need • More realistic representation of transit access inPublic Transport (PT) • Improved model accuracy for both highwayand transit models • Consistent approach for the modeling and planning community in the State

  4. Reviewers • FDOT • FHWA • MTF Model Advancement Committee • MTF Data Committee • Other interested parties outside Florida

  5. Recommendation Checklist • The number of people per TAZ should be greater than 1,200, but less than 3,000 for the base- and future-years • Each TAZ yields less than 15,000 person trips in thebase- and future-years • The size of each TAZ is between 0.25 to one squaremile in area • There is a logical number of intrazonal trips in each zone based on the mix and density of the land use • There are no irregular-shaped TAZs • Each centroid connector loads less than 10,000 to 15,000 vehicles per day in the base- and future-year • The study area is large enough so that nearly all (over 90 percent) of the trips begin and end within the study area

  6. Recommendation Checklist (continued) • The TAZ structure is compatible with thebase- and future-year highway and transit network • The centroid connectors represent realistic access points to the highway network • Transit access is represented realistically • The TAZ structure is compatible with census, physical, political, and planning district/sector boundaries • The TAZs are based on homogeneous land uses, when feasible, in both the base- and future-year and consider future DRIs • Special generators and freight generators/attractors are isolated within their own TAZ

  7. Delineating TAZs in the Base-Year Model Figure 3.3 Blocks versus Block Groups versus Census Tracts • Zone size and quantity • Boundary compatibility • Socioeconomic data • Access • Centroid connectors • Existing transportationfacilities • TAZ numbering

  8. Delineating TAZs in the Base-Year Model Zone Size and Quantity • Size of zones depends on intended use of model • Large-sized zones for system or statewide planning • Statewide models • TAZs can be larger than the arterial grid • Up to approximately 20,000 persons per zone • Medium-sized zones for arterial planning • Regional or MPO models • Two or more arterials should not traverse the TAZ in any direction • Up to approximately 4,000 persons per zone • Small-sized zones for corridor analysis • Corridor level or subarea models • TAZs in a corridor or subarea should be more refined • Should be greater than 1,200, but less than 3,000persons per zone

  9. Delineating TAZs in the Base-Year Model Boundary Compatibility Figure 3.1 Delineating TAZs Consistent with the Physical Geography • Physical geography • Census geography • Political geography • Planning district/sector boundaries • Irregular zone geography Figure 3.2 Delineating TAZs Based on Permanent Barriers

  10. Delineating TAZs in the Base-Year Model Socioeconomic Data Figure 3.10 Delineating TAZs Based on Clusters of Similar Land Uses • Homogeneousland uses,where feasible • Special generators • Trips per zone • Developments ofregional impact

  11. Delineating TAZs in the Base-Year Model Access Figure 3.11 Over-Estimating Walk Access to Transit • Transit access • Freight/intermodal facilities

  12. Delineating TAZs in the Base-Year Model Centroid Connectors • Represent realistic roadway and transit access • Should not cross man-made or natural barriers • Include a sufficient number of centroid connectors to avoid loading too many trips to one roadway network link • Do not connect centroid connectors at intersectionsor directly to interstate ramps • When two centroid connectors are connected to the same roadway segment, the access points should be separated by a certain distance The Wrong Way The Right Way Figure 3.20 Placement of Centroid Connectors Relative to Intersectionsand Interstate Ramps

  13. Delineating TAZs in the Base-Year Model Existing Transportation Facilities Figure 3.14 Delineating TAZs Based on Transit Access • Rail lines • Limited access highways • Arterial streets and roadways • Collector streets and roadways

  14. Delineating TAZs in the Base-Year Model TAZ Numbering • Recommended that TAZ numbers begin with oneand be consecutive • Regional models may set aside a specific range of TAZ numbers for both TAZs and dummy zones for each county • Create TAZ equivalency tables to provide a list of thenew zone numbers that were split from the originalzone numbers

  15. Future Year TAZ Considerations Figure 4.1 Defining the TAZ Structure Based on Future Corridors • Plannedtransportationcorridors • Developments ofregional impact • Populationand tripsper zone Figure 4.2 Defining the TAZ Structure Based on Future DRI

  16. Future Year TAZ ConsiderationsPopulation and Trips per Zone • Anything more than 15,000 trips per day or 1,200 to 3,000 people per TAZ exceeds the recommended zone size • The Census Bureau is currently considering increasing the minimum number of persons per block group (and potentially TAZs) to 1,200 persons (previously 600) or 480 households. The existing maximum thresholds of 3,000 persons and 1,200 households per block group remain unchanged • Often times, a TAZ may not have as many people or generate that many daily trips in the base-year • However, with the future-year land use, it may verywell push the population or daily trips over the thresholds noted above

  17. Splitting TAZs • Network data impacts • Socioeconomicdata impacts • Boundary shiftsand zone aggregations • Zones beyondmodel boundary • Revalidation Figure 5.1 Splitting Household Data into New TAZs

  18. Topics Requiring Further Research • Mixed land uses • Delineating TAZs based on homogenous land uses is notalways feasible • CBDs and neo-traditional developments make it difficult to isolate employees from households • Dynamic subzoning • Potential solution to mixed land use issue • Includes multiple centroids within one zone; one to represent employment and another to represent households • Allows different access points onto the network by having one set of centroid connectors for employment and another for households • Would require further research, including the numberingof subzones

  19. Where to Find the Paper • White Paper is on-line at www.fsutmsonline.net

  20. Questions or Comments? Discussion

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