Methods for Conducting a Large-Scale GPS-Only Survey of Households. Greg Giaimo & Rebekah Anderson , Ohio Department of Transportation Laurie Wargelin & Jason Minser , Abt SRBI. 13th TRB National Transportation Planning Applications Conference May 11th, 2011. History.
Methods for Conducting a Large-Scale GPS-Only Survey of Households
Greg Giaimo & Rebekah Anderson, Ohio Department of Transportation
Laurie Wargelin & Jason Minser, Abt SRBI
13th TRB National Transportation Planning Applications Conference
May 11th, 2011
Cincinnati’s last HIS was conducted in 1995 by MORPACE
2010 Model Update – Wanted a new HIS
GPS survey design chosen due to known problems with travel under-reporting
Funded through ODOT SPR Research
Test logistical issues for large scale GPS deployment such as:
Recruitment & child diary surveys needed to supplement GPS data collection
Lack of trip purpose, mode, occupancy, or cost data from passive GPS devices
Use of a Prompted Recall survey to impute the trip purpose and mode.
Participation Rates by demographic category
Address based sample frame
Internet recruiting option
GPS units for all HH members > 12
Simple diary for children < 12
Obtain home, usual work, school, shop locations to aid in GPS interpretation
One year “average conditions” data collection period
Follow on prompted recall survey
Recruited 5,564 households
4,238 recruited households in the 8 County area received GPS units (due to GPS unit losses discussed later)
Obtained 2,583 complete GPS surveys (not including “no travel” households (61%)
All households were asked to complete a 1 day Internet Prompted Recall Survey obtaining 601 completes
All members in a household over 12 years old (given a GPS unit), completing 1 concurrent day of full GPS recording.
If a household member did not travel on a day when the other(s) did fully record, it counts as a complete.
GPS HH completes include households where 4+ persons were assigned a GPS unit and a single household member failed to record complete travel on a concurrent day.
GPS doesn’t lie or forget
Apparently higher recruitment to complete data completion rates in diary surveys masks incomplete results which result in low trip rates
Due to the cost of the GPS devices, the survey was be conducted over 1 year to allow more device cycling.
Implies we obtained “average” vs. “typical” conditions, hence:
Not concerned so much with the precise days surveyed
More concerned that sample be maintained consistently month to month
The recruited households received:
GPS devices (People 13+)
Child diaries (Children under 13)
Individual survey forms: work/school address, no travel days
Household/Vehicle survey form: 2 most frequented grocery stores, odometer readings
Every member of the household aged 13 and over received a GPS device
Children 12 and under had a child’s diary which avoided detailed location questions
Traveled with anotherHousehold Member
This allows for better imputation of destination purposes.
Low additional respondent burden
Better chance to get a completed day (though this can introduce a self-selection bias)
Can use additional travel days in disaggregate model estimation
GPS units returned by:
Depositing in either Fed Ex or US Postal drop boxes
Calling the project 1-800 number to arrange a Fed EX or personal courier pick-up
Follow up phone calls and Internet reminders to arrange courier pick-ups as necessary
2,583 households completed the GPS study, for a 60.3% response rate. However, an additional 1,326 recruited household did not receive GPS units, resulting in an overall lower than targeted sample (target equaled 3,000 households)
Discrepancy points to a need for tighter coordination of recruitment survey conducted by call center and GPS deployment team’s unit availablity.
By study’s end, 565 of the 833 units deployed were not returned (68%).
256 units lost (45%) were assigned to 4+ person households
# times ranged from 1 – 28
Average was 10 times
7 were returned damaged
Mode is imputed using the 85th percentile highest speed, acceleration and deceleration, and matching to the street networks and bus/train networks in a GIS.
Frequency and duration of visits
Matched address (work, school, grocery)
Trips by Time, Location and Mode
Accel/decel rates, bus routes, stop pattern and school end for school bus
Bike/auto difficult to distinguish
Mode 59% PR match rate
15% missed due to poor bus route data
12% difference due to bad PR response
Purpose 53% PR match rate
28% inferred as closely as possible without PR survey (PR survey gives more detailed categories)
9% difference due to bad PR response