Supplementing Census Data SANDAG Case Studydownload.ctpp.transportation.org/Future/presentations/5-12-8-McFarlane.pdfTravel Time Surveys Total 486 498 12 2% 515 539 24 5% SanYsidro-Downtown

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)



Buildings, not units

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



Selected structure types

Census (SF3)Resolution: Block groups (2,200)Limitations: Self-reported



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


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

Speed Surveys/Transportation ModelsResolution: TAZs (4,600)


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

Speed Surveys/Transportation ModelsResolution: TAZs (4,600)


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


Transit On-Board SurveysResolution: Small summary areas


Trip TablesTrip TablesCensus (CTPP)Resolution: CTPP zones (500)




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



Documents

Supplementing Census Data SANDAG Case Studydownload.ctpp.transportation.org/Future/presentations/5-12-8-McFarlane.pdfTravel Time Surveys Total 486 498 12 2% 515 539 24 5% SanYsidro-Downtown