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ODOT, Greg Giaimo and Rebekah AndersonOKI, Andrew Rohne

Laurie Wargelin, Abt SRBI, Prime Peter Stopher, PlanTrans, GPS

Kevin Tierney, Cambridge Systematics, SamplingSharon O’Connor, Resource Systems Group, Internet

The Greater Cincinnati Area The Greater Cincinnati Area Large-Scale (100%) GPS-BasedLarge-Scale (100%) GPS-Based

Household Travel SurveyHousehold Travel Survey

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Introduction

Quoting from the RFP Research Objectives . .

“This is the first large scale GPS-based survey conducted in the United States, and therefore, beyond the various logistical issues, it is uncertain to what extent a GPS-based survey is able to capture all the information available in a diary-based survey. “

This presentation describes the processes used for the Spring 2009 GPS survey pilot, and discusses early findings.

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Goals . . .

Reduce substantial respondent burden inherent in traditional travel diary recordings

Reduce under-reporting of trip data

Increase representative response rates

Provide the detailed geographic information on route, speed, and location not captured by traditional diary methods that can influence the way travel is modeled

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Sample Design

Sample Size – Record three days travel -- Complete a minimum of one-day trip records for all members of 4,000 households.

No diary recordings (if over age 12)--GPS RECORDING ONLY.

Address-Based Sampling - so that cell-only households are included.

Exclusion of these households is an increasing problem with traditional RDD sampling.

Estimates of cell-only households are 15-30% depending on metropolitan area.

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Phone “Matched” and “Un-Matched” Sample with Address-Based Sampling

The randomly selected address-based sample is from US Postal Service delivery sequencing files.

Sample addresses are matched with known land based phone numbers. (For the pilot, 60% of addresses were matched with a land based phone number–-about the same as reverse matching for RDD sample.)

Addresses without known phone numbers (“Un-matched”) consist of households with unlisted numbers, no phone, or increasingly of cell phone-only households (total 40%).

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Recruitment With an Address-Based Sample

Address-Based Data Collection

Procedures

Phone Matched Sample

Advance Letter with Internet

Password

Un-Matched Sample

Advance Letter, Return Postcard,

and Internet Password

Phone Recruit Internet Recruit

Postcard Return

with Phone # or Call-in to 1-800 # - Then Phone

Recruit

Deploy GPS Units and Person/

Household Forms

Deploy GPS Units and Person/

Household Forms

Internet Recruit

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Address-based sample allows oversampling of transit access areas and University off-campus areas (student households) by census block group—not fully possible with RDD sampling.

PUMS data (aggregated by block group) can be used for monitoring recruits by combinations of household size, # of workers, # of vehicles, and HH lifestyle cycles (student, with/without children, retired).

Advance letters can be sent to all sample households—not possible with an RDD sample.

Other Advantages of Address-Based Sampling

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Survey Design- GPS Capabilities

Personal GPS units so that all travel, not just vehicle trips, are recorded. Can be carried in a pocket or purse, or clipped on a belt or a wrist band.

Goal of recording three days of travel.

Every member of the household 13 yearsand older carries a GPS unit for

three days.

The GPS devices will be deployed over a one year time period beginning in July of 2009.

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Besides GPS units for all over 12, we collect limited children’s activities and travel information in a diary format (to link with other household members’ travel). Objective is to reduce burden and meet child privacy concerns.

Six-minute phone or Internet recruitment interview--three-day travel periods assigned.

Short-form household and person information forms distributed and collected with GPS units.

Forms collect: (1) work and school locations, (2) two most frequent household shopping locations, and (3) GPS usage status for each member, each day.

Survey Design – Pilot Implementation

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Short-Form Materials Piloted with Deployment GPS Units

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Goal is to develop an efficient (low cost) GPS data collection process:

GPS unit and forms packages sent by Fed Ex GPS units return methods piloted:

(1) Participants provided with pre-paid shipping packages that can be deposited in either Fed Ex or US Postal Service drop boxes

(2) Call the project 1-800 number to arrange a Fed Ex or personal courier pick-up.

(3) Follow-up phone calls and Internet reminders to arrange courier pick-ups as necessary.

Survey Design – Pilot Implementation

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GPS Data Imputation and Verification – PlanTrans Processing Methodology

Imputation of Trip Ends and Mode - Using a set of rules that include movement of the GPS for 2 minutes or more-or lack of movement, or a significant change in speed, indicating a different mode being used.

Prompted Recall (PR) Verification - Return of respondents’ travel (in Google Map form) in a web-based format for verification. Detailed ability to correct travel and purpose information, and add travel cost (fare, driving and parking costs) and vehicle occupancy for each trip.

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Prompted Recall Web Format

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Survey Design - GPS Data Processing and Imputation

PlanTrans imputes purpose using the frequency and duration of visits, the match to one of the collected addresses (home, workplace, school, frequent shops), and to available GIS land use data.

PlanTrans is also developing an additional rule-based procedure for occupancy by family members by matching trips from different family members by time, location, and mode.

With the aid of the prompted recall, Artificial Intelligence software is being trained, and these results will be applied to rule-based software. In this process, PlanTrans will attempt to add the capabilities to impute occupancy, driver/passenger status, and possibly parking costs and bus fares.

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Pilot Sample Plan Designed to Test Response Rates and Incentives

Equal sample for Higher Transit Access and Lower Transit Access geographic areas

Equal sample for Phone Matched and Non-Matched Sample

Matched Sample offered $0 or $10 incentive to complete

Non-Matched Sample offered $10 or $25 incentive to complete

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Pilot Sample Results

81

19

0

20

40

60

80

100

Matched UnMatched

0

20

40

60

80

100

HigherTransitAccessLowerTransitAccess

% %

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Pilot Sample Results- Incentives

8

6

1113

0

20

$10 $25

RecruitComplete

Matched Sample Un-Matched Sample

42 4539

36

0

20

40

60

$0 $10

RecruitComplete

%%

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Pilot Sample Results- by Income

37

60

0

20

40

60

80

100

<$50,000$50,000+

Overall Completes to Recruits

Completes to Recruits by Incentive

38

53

34

61

50

86

0

20

40

60

80

100

$0 $10 $25

<$50,000$50,000+

% %

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Processing and Verification of GPS Data Files for Pilot

PlanTrans Processes the GPS Data Files Twice:

First for the Prompted Recall Survey After the Prompted Recall Survey:

Deletions or additions are made to fix trips Mode of travel is rechecked and identified for

each trip Purpose of trip is rechecked and identified

Trip File is Created

Monthly or Bi-Monthly Completed Data is Delivered to the Client for Rechecking

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Pilot Results - Address-Based Phone Match vs. Non-Match

Internet was the most viable means of obtaining recruits from households without land-based phones.

Additionally, 19% of recruits from the phone matched sample responded to the advance letter by completing the recruitment on-line.

Only one phone number was obtained from the unmatched sample via a return postcard/reply to a hot button issue survey.

Regardless of recruitment method, completion rates for matched and unmatched sample were equivalent – once recruited.

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Demographics of Pilot Internet Responders

The Advance Letter to the Un-Matched address-based sample (households without known land phones) was successful at recruiting a substantial percent of households to the GPS-Based Survey via the Internet.

This was particularly true for younger age group households (18 to 34 years old) with only cell phones.

These households are typically under-represented in traditional Household Travel Surveys.

As would be expected, there were also a higher number of student households in this group.

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Demographics of Pilot Internet Responders - Age

MatchedPhone

Recruits

Matched Internet Recruits

Un-Matched Internet Recruits

Contact Person 18-34 Years

Old

22% 17% 58%Almost

Entirely Cell-Only

Households

These households are typically under-represented in Diary Household Travel Surveys and subsample GPS surveys also show their trips and tours to be under-reported.

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Pilot Representativeness of Completed Households

A very representative sample was recruited and completed by HH Size.

The requirement that all household members age 13 or older carry GPS units did not prove to be a “respondent burden” barrier.

A representative sample was completed by number of vehicles.

However, while an appropriate percent of zero vehicle

households were recruited, extra effort (incentives?) will be needed to complete zero vehicle households.

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Pilot Representativeness of Completed Households

Table 1: Distribution of Pilot Completed Households by Size

Household Size Percentage of HH Recruitments

Percentage of HH Completes

PUMS 2000 data Difference

1 29.2% 29.3% 27.3% 2.0% 2 31.1% 34.1% 32.0% 2.1% 3 15.3% 15.9% 16.6% -0.7%

4 or more 24.4% 20.7% 24.1% -3.4% Total 100.0% 100.0% 100.0%

Table 2: Distribution of Pilot Completed Households by Autos Available

Autos available to Household

Percentage of HH Recruitments

Percentage of HH Completes

PUMS 2000 data Difference

0 9.1% 2.4% 9.7% -7.3% 1 28.2% 28.0% 32.3% -4.3% 2 40.2% 46.3% 38.8% 7.5%

3 or more 22.5% 23.2% 19.2% 4.0% Total 100.0% 99.9% 100.0%

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Pilot Representativeness of Completed Households – Con’t

The completed pilot sample was fully representative by lifestyle/family type.

The higher percent of households with zero workers was not due to oversampling of retirees. May be attributable to current economic conditions.

The pilot was successful at recruiting low income households, but incentives/extra effort will be required to complete these households.

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Pilot Representativeness of Completed Households – Con’t

Household Type Percent of HH Recruitments

Percent of HH

Completes

PUMS 2000 data

Difference

Adult Household 48.3% 43.9% 46.0% -2.1% Household with Children 32.5% 34.1% 36.6% -2.5%

Retiree Household 14.8% 18.3% 14.5% 3.8% Adult Student Household 4.3% 3.7% 2.9% 0.8%

Total 99.9% 100.0% 100.0%

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Pilot Representativeness of Completed Households – Con’t

Table 3: Distribution of Pilot Completed Households by Household Workers

Number of Workers in Household

Percentage of HH Recruitments

Percentage of HH

Completes

PUMS 2000 Data

Difference

0 29.7% 32.9% 24.0% 8.9% 1 37.8% 35.4% 37.4% -2.0% 2 26.8% 30.5% 31.3% -0.8%

3 or more 5.7% 1.2% 7.3% -6.1% Total 100.0% 100.0% 100.0%

Table 4: Distribution of Pilot Completed Households by Household Income

Income Category Percentage of HH Recruitments

Percentage of HH

Completes

PUMS 2000 data

Difference

Below $25,000 21.8% 9.1% 20.6% -11.5% $25,000 to less

than $50,000 26.9% 28.6% 25.1% 3.4%

$50,000 to less than $75,000

19.3% 20.8% 20.2% 0.6%

$75,000 or more 32.0% 41.6% 34.1% 7.4% Total 100.0% 100.0% 100.0%

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Primary Logistical Problems – Return of GPS Units and Some GPS Battery Outages

Retrieving GPS units in a timely manner for redeployment – with minimum loss - is a logistical and cost problem

Loss rate for pilot was 2.7 percent--mostly among low income/urban households.

More units needed, higher incentives, longer field time?

Battery outages over three days – need to supply chargers

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ODOT GPS-Based Pilot Summary to Date

Address-based sampling can be successful in recruiting cell-phone only households to a GPS-Based HTS via an Internet recruit.

GPS household completion rates are adequate and representative.

Requiring every household member (over 12) to carry a GPS unit for three days was not considered an undue burden – paperwork was greatly reduced.

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ODOT GPS-Based Pilot Summary to Date

The child diary needs to be kept simple - perhaps only one day travel is needed.

Significant incentives and additional efforts are needed to complete unmatched households, and households with low-incomes and/or zero vehicles.

Added trip accuracy reporting and the value of route and location with speed data (as collected via GPS) needs to be demonstrated upon completion of the pilot PR and trip files in early June 2009.