FDOT Systems Planning White Paper A Recommended Approach

FDOT Systems Planning White Paper A Recommended Approach to Delineating Traffic Analysis Zones in Florida Transportation leadership you can trust.

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 1

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 in Public Transport (PT) • Improved model accuracy for both highway and transit models • Consistent approach for the modeling and planning community in the State 2

Reviewers FDOT FHWA MTF Model Advancement Committee MTF Data Committee Other interested parties outside Florida 3

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 the base- and future-years The size of each TAZ is between 0. 25 to one square mile 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 4

Recommendation Checklist (continued) The TAZ structure is compatible with the base- 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 5

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 transportation facilities TAZ numbering 6

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, 000 persons per zone 7

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 8

Delineating TAZs in the Base-Year Model Socioeconomic Data Homogeneous land uses, where feasible Special generators Trips per zone Developments of regional impact 9 Figure 3. 10 Delineating TAZs Based on Clusters of Similar Land Uses

Delineating TAZs in the Base-Year Model Access Transit access Freight/ intermodal facilities 10 Figure 3. 11 Over-Estimating Walk Access to Transit

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 intersections or 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 Intersections and Interstate Ramps 11

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 12

Delineating TAZs in the Base-Year Model TAZ Numbering Recommended that TAZ numbers begin with one and 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 the new zone numbers that were split from the original zone numbers 13

Future Year TAZ Considerations Figure 4. 1 Defining the TAZ Structure Based on Future Corridors Planned transportation corridors Developments of regional impact Population and trips per zone 14 Figure 4. 2 Defining the TAZ Structure Based on Future DRI

Future Year TAZ Considerations Population 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 very well push the population or daily trips over the thresholds noted above 15

Splitting TAZs Network data impacts Socioeconomic data impacts Boundary shifts and zone aggregations Zones beyond model boundary Revalidation 16 Figure 5. 1 Splitting Household Data into New TAZs

Topics Requiring Further Research Mixed land uses • Delineating TAZs based on homogenous land uses is not always 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 numbering of subzones 17

Where to Find the Paper White Paper is on-line at www. fsutmsonline. net 18

Discussion Questions or Comments? 19