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Supplementing Census Data SANDAG Case Study
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Page 1: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Supplementing Census DataSANDAG Case Study

Supplementing Census DataSANDAG Case Study

Page 2: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

DEMOGRAPHIC DATA

Page 3: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Dwelling Unit CountsDwelling Unit Counts

Census (SF1)Resolution: Blocks (25,700)

Property Record Files Resolution: Parcels (800,000)

Aerial Photographs Resolution: Individual buildingLimitations: Small areas only Buildings, not units

Census (SF1)Resolution: Blocks (25,700)

Property Record Files Resolution: Parcels (800,000)

Aerial Photographs Resolution: Individual buildingLimitations: Small areas only Buildings, not units

Page 4: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Structure TypeStructure TypeCensus (SF3)Resolution: Block groups (2,200)Limitations: Self-reported

Property Record FilesResolution: Parcels (800,000)

Aerial Photographs Resolution: 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 Photographs Resolution: Individual buildingLimitations: Small areas only Selected structure types

Page 5: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Employment EstimatesEmployment EstimatesCensus (CTPP)Resolution: CTPP zones (500)

ES202 Files Resolution: Individual employersLimitations: Confidentiality issues

Missing employersMultiple Sites

Derived from Building Floor AreaResolution: Parcels (800,000)

Census (CTPP)Resolution: CTPP zones (500)

ES202 Files Resolution: Individual employersLimitations: Confidentiality issues

Missing employersMultiple Sites

Derived from Building Floor AreaResolution: Parcels (800,000)

Page 6: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Household IncomeHousehold IncomeCensus (SF3)Resolution: Block groups (2,200)

State Income Tax Returns Resolution: Tracts (600)Limitations: Confidentiality issues Definitional differences

Complex process

Census (SF3)Resolution: Block groups (2,200)

State Income Tax Returns Resolution: Tracts (600)Limitations: Confidentiality issues Definitional differences

Complex process

Page 7: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Case StudyParcel Level Dwelling Units

Page 8: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

MGRA Geography

Page 9: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Irregular Geography

Page 10: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Transit Access

Page 11: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Parcel and MGRA Geography

Page 12: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Block Group Check

Page 13: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Block Counts and Land Use

Page 14: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Residential Buildings

Page 15: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Problem AreasProblem Areas

Census Structure typesGeo-coding qualityBlock definitionsSenior housing

Property Record Files Units on public/non-taxable land

Both Units under construction

Census Structure typesGeo-coding qualityBlock definitionsSenior housing

Property Record Files Units on public/non-taxable land

Both Units under construction

Page 16: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

TRANSPORTATION DATA

Page 17: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Number of VehiclesNumber of VehiclesCensus (SF3)

Resolution: Block groups (2,200)

Department of Motor Vehicles

Resolution: Countywide

Home Interview Surveys

Resolution: Large summary areas

Limitations: Sample bias

Census (SF3)

Resolution: Block groups (2,200)

Department of Motor Vehicles

Resolution: Countywide

Home Interview Surveys

Resolution: Large summary areas

Limitations: Sample bias

Page 18: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Average Trip Length (Minutes)Average Trip Length (Minutes)Census (CTPP)Resolution: CTPP zones (500)Limitations: Self-reported

Speed Surveys/Transportation Models Resolution: TAZs (4,600)

Home Interview Surveys Resolution: Large summary areasLimitations: Sample bias

Census (CTPP)Resolution: CTPP zones (500)Limitations: Self-reported

Speed Surveys/Transportation Models Resolution: TAZs (4,600)

Home Interview Surveys Resolution: Large summary areasLimitations: Sample bias

Page 19: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Transit Mode SharesTransit Mode SharesCensus (CTPP)

Resolution: CTPP zones (500)

Transit On-Board Surveys

Resolution: Small summary areas

Home Interview Surveys

Resolution: Very large summary areas

Limitations: Sample bias

Census (CTPP)

Resolution: CTPP zones (500)

Transit On-Board Surveys

Resolution: Small summary areas

Home Interview Surveys

Resolution: Very large summary areas

Limitations: Sample bias

Page 20: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Trip TablesTrip TablesCensus (CTPP)

Resolution: CTPP zones (500)

Home Interview Surveys

Resolution: Very large summary areas

Limitations: Sample bias

Census (CTPP)

Resolution: CTPP zones (500)

Home Interview Surveys

Resolution: Very large summary areas

Limitations: Sample bias

Page 21: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Case StudyAuto Travel Times

Page 22: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Travel Time SurveysTravel Time Surveys

Route

AM PM

Observed Modeled Difference Observed Modeled Difference

Calsbad-Escondido 26 30 4 15% 26 27 1 4%

Chula Vista-Sorrento Mesa 54 54 0 0% 66 71 5 8%

Downtown-Sorrento Mesa 29 32 3 10% 29 35 6 21%

El Cajon-Downtown 28 29 1 4% 25 30 5 20%

Escondido-Calsbad 39 35 -4 -10% 43 40 -3 -7%

Escondido-Downtown 62 64 2 3% 59 64 5 8%

Escondido-Kearny Mesa 55 47 -8 -15% 44 46 2 5%

MidCity-Kearny Mesa 15 16 1 7% 20 16 -4 -20%

Mid City-Sorrento Mesa 26 31 5 19% 42 42 0 0%

Oceanside-Downtown 63 62 -1 -2% 65 62 -3 -5%

Rancho Bernado-Sorrento Mesa 33 35 2 6% 51 50 -1 -2%

Sorrento Mesa-Downtown 29 27 -2 -7% 25 28 3 12%

SanYsidro-Downtown 27 36 9 33% 20 28 8 40%

Total 486 498 12 2% 515 539 24 5%

Page 23: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

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

Page 24: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

GPS Coverage

Page 25: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

GPS PointsGPS Points

Page 26: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Freeway Speed Comparison63.3

53.350.8

58.0

40.7 39.9

0

10

20

30

40

50

60

70

Off-Peak AM Peak PM Peak

Time Period

Sp

eed

(M

PH

)

GPS

Model

Page 27: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Arterial Speed Comparison

26.3 26.3

23.722.7 22.1 21.6

0

5

10

15

20

25

30

Off-Peak AM Peak PM Peak

Time Period

Sp

ee

d (

MP

H)

GPS

Model

Page 28: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

0

5

10

15

20

25

30

35

Minutes Miles Speed

CTPP

Model

CTPP – Model Comparison

-4%

-11%

-7%

Page 29: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Modeled Travel Times Minutes to CBD by AutoModeled Travel Times

Minutes to CBD by Auto

Page 30: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

CTPP Travel TimesMinutes to CBD by Auto

CTPP Travel TimesMinutes to CBD by Auto

Page 31: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Modeled Travel Times Minutes to Suburb by Auto

Modeled Travel Times Minutes to Suburb by Auto

Page 32: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

CTPP Travel TimesMinutes to Suburb by Auto

CTPP Travel TimesMinutes to Suburb by Auto

Page 33: Supplementing Census Data SANDAG Case Study. DEMOGRAPHIC DATA.

Supplementing Census DataSANDAG Case Study

Supplementing Census DataSANDAG Case Study