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Supplementing Census DataSANDAG Case Study
Supplementing Census DataSANDAG Case Study
DEMOGRAPHIC DATA
Dwelling Unit CountsDwelling Unit CountsCensus (SF1)Resolution: Blocks (25,700)
Property Record FilesResolution: Parcels (800,000)
Aerial PhotographsResolution: Individual buildingLimitations: Small areas only
Buildings, not units
Census (SF1)Resolution: Blocks (25,700)
Property Record FilesResolution: Parcels (800,000)
Aerial PhotographsResolution: Individual buildingLimitations: Small areas only
Buildings, not units
Structure TypeStructure TypeCensus (SF3)Resolution: Block groups (2,200)Limitations: Self-reported
Property Record FilesResolution: Parcels (800,000)
Aerial PhotographsResolution: Individual buildingLimitations: Small areas only
Selected structure types
Census (SF3)Resolution: Block groups (2,200)Limitations: Self-reported
Property Record FilesResolution: Parcels (800,000)
Aerial PhotographsResolution: Individual buildingLimitations: Small areas only
Selected structure types
Employment EstimatesEmployment EstimatesCensus (CTPP)Resolution: CTPP zones (500)
ES202 FilesResolution: Individual employersLimitations: Confidentiality issues
Missing employersMultiple Sites
Derived from Building Floor AreaResolution: Parcels (800,000)
Census (CTPP)Resolution: CTPP zones (500)
ES202 FilesResolution: Individual employersLimitations: Confidentiality issues
Missing employersMultiple Sites
Derived from Building Floor AreaResolution: Parcels (800,000)
Household IncomeHousehold IncomeCensus (SF3)Resolution: Block groups (2,200)
State Income Tax ReturnsResolution: Tracts (600)Limitations: Confidentiality issues
Definitional differencesComplex process
Census (SF3)Resolution: Block groups (2,200)
State Income Tax ReturnsResolution: Tracts (600)Limitations: Confidentiality issues
Definitional differencesComplex process
Case StudyParcel Level Dwelling Units
MGRA Geography
Irregular Geography
Transit Access
Parcel and MGRA Geography
Block Group Check
Block Counts and Land Use
Residential Buildings
Problem AreasProblem AreasCensus Structure typesGeo-coding qualityBlock definitionsSenior housing
Property Record FilesUnits on public/non-taxable land
BothUnits under construction
Census Structure typesGeo-coding qualityBlock definitionsSenior housing
Property Record FilesUnits on public/non-taxable land
BothUnits under construction
TRANSPORTATION DATA
Number of VehiclesNumber of VehiclesCensus (SF3)Resolution: Block groups (2,200)
Department of Motor VehiclesResolution: Countywide
Home Interview SurveysResolution: Large summary areasLimitations: Sample bias
Census (SF3)Resolution: Block groups (2,200)
Department of Motor VehiclesResolution: Countywide
Home Interview SurveysResolution: Large summary areasLimitations: Sample bias
Average Trip Length (Minutes)Average Trip Length (Minutes)Census (CTPP)Resolution: CTPP zones (500)Limitations: Self-reported
Speed Surveys/Transportation ModelsResolution: TAZs (4,600)
Home Interview SurveysResolution: Large summary areasLimitations: Sample bias
Census (CTPP)Resolution: CTPP zones (500)Limitations: Self-reported
Speed Surveys/Transportation ModelsResolution: TAZs (4,600)
Home Interview SurveysResolution: Large summary areasLimitations: Sample bias
Transit Mode SharesTransit Mode SharesCensus (CTPP)Resolution: CTPP zones (500)
Transit On-Board SurveysResolution: Small summary areas
Home Interview SurveysResolution: Very large summary areasLimitations: Sample bias
Census (CTPP)Resolution: CTPP zones (500)
Transit On-Board SurveysResolution: Small summary areas
Home Interview SurveysResolution: Very large summary areasLimitations: Sample bias
Trip TablesTrip TablesCensus (CTPP)Resolution: CTPP zones (500)
Home Interview SurveysResolution: Very large summary areasLimitations: Sample bias
Census (CTPP)Resolution: CTPP zones (500)
Home Interview SurveysResolution: Very large summary areasLimitations: Sample bias
Case StudyAuto Travel Times
Travel Time SurveysTravel Time Surveys
5%245395152%12498486Total
40%8282033%93627SanYsidro-Downtown
12%32825-7%-22729Sorrento Mesa-Downtown
-2%-150516%23533Rancho Bernado-Sorrento Mesa
-5%-36265-2%-16263Oceanside-Downtown
0%0424219%53126Mid City-Sorrento Mesa
-20%-416207%11615MidCity-Kearny Mesa
5%24644-15%-84755Escondido-Kearny Mesa
8%564593%26462Escondido-Downtown
-7%-34043-10%-43539Escondido-Calsbad
20%530254%12928El Cajon-Downtown
21%6352910%33229Downtown-Sorrento Mesa
8%571660%05454Chula Vista-Sorrento Mesa
4%1272615%43026Calsbad-Escondido
DifferenceModeled ObservedDifferenceModeled Observed
PMAMRoute
California Statewide Travel Survey
• 1,200 San Diego County Households• 180 Households with GPS-Equipped
Vehicles • 1,000 GPS trips out of 4,700 total survey
trips• February-October 2001• GeoStats
GPS Coverage
GPS PointsGPS Points
Freeway Speed Comparison63.3
53.3 50.8
58.0
40.7 39.9
0
10
20
30
40
50
60
70
Off-Peak AM Peak PM PeakTime Period
Spee
d (M
PH)
GPSModel
Arterial Speed Comparison26.3 26.3
23.722.7 22.1 21.6
0
5
10
15
20
25
30
Off-Peak AM Peak PM Peak
Time Period
Spee
d (M
PH)
GPSModel
0
5
10
15
20
25
30
35
Minutes Miles Speed
CTPPModel
CTPP – Model Comparison
-4%
-11%
-7%
Modeled Travel Times Minutes to CBD by AutoModeled Travel Times
Minutes to CBD by Auto
CTPP Travel TimesMinutes to CBD by Auto
CTPP Travel TimesMinutes to CBD by Auto
Modeled Travel Times Minutes to Suburb by Auto
Modeled Travel Times Minutes to Suburb by Auto
CTPP Travel TimesMinutes to Suburb by Auto
CTPP Travel TimesMinutes to Suburb by Auto
Supplementing Census DataSANDAG Case Study
Supplementing Census DataSANDAG Case Study
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