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Using an Odometer and a GPS Panel to Evaluate Travel Behaviour Changes

Using an Odometer and a GPS Panel to Evaluate Travel Behaviour Changes. Peter Stopher and Natalie Swann Institute of Transport and Logistics Studies The University of Sydney and Camden FitzGerald Parson Brinkerhoff, Sydney April 2007. Introduction.

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Using an Odometer and a GPS Panel to Evaluate Travel Behaviour Changes

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  1. Using an Odometer and a GPS Panel to Evaluate Travel Behaviour Changes Peter Stopher and Natalie Swann Institute of Transport and Logistics Studies The University of Sydney and Camden FitzGerald Parson Brinkerhoff, Sydney April 2007

  2. Introduction • Policies often aimed at changing travel behaviour • Rarely are the changes monitored to see if the policy was successful • Often the changes expected are within the error levels of self-report surveys Using an Odometer and a GPS Panel to Evaluate ...

  3. Introduction • A policy of major interest in Australia is Voluntary Travel Behaviour Change (VTBC or TravelSmart) • Based on improving household information about alternatives to current travel • Expectation is that it will result in reduced VKT by private car and possibly increased walk, bicycle, transit use, and car occupancy Using an Odometer and a GPS Panel to Evaluate ...

  4. Introduction • TravelSmart is a relatively cheap strategy compared to capital projects • Would be very cost-effective if it reduced car VKT by even 3-4 percent • Standard diary surveys have been shown to be in error by 20 percent or more on average • Self-reporting of distance travelled is potentially even more in error Using an Odometer and a GPS Panel to Evaluate ...

  5. An Innovative Approach • Use of panels to monitor change • Measurement of the panel begins prior to policy introduction • Panel continues until some period of time after introduction • Method one – quarterly odometer survey • Method two – annual or semi-annual GPS survey Using an Odometer and a GPS Panel to Evaluate ...

  6. An Innovative Approach • Panels – recruit households who are asked to repeat the survey at prescribed intervals • Attrition – recruit additional households in each wave • Panel reduces error in measuring change • Panel members report changes in demographics on each wave Using an Odometer and a GPS Panel to Evaluate ...

  7. An Innovative Approach • Odometer survey – request households to provide current odometer readings from each household vehicle and the date on which they take the reading • If a car is bought or sold, then beginning/ending odometer reading is requested and date of acquisition/sale • Readings are requested every quarter Using an Odometer and a GPS Panel to Evaluate ...

  8. An Innovative Approach • GPS survey involves carrying a GPS device for up to 28 days • Everyone over age 14 in household is asked to take a device • Survey is repeated either annually or semi-annually Using an Odometer and a GPS Panel to Evaluate ...

  9. An Innovative Approach • Three elements to the pilot evaluation • Quarterly odometer panel of 200 households in South Australia and 200 in Victoria • Six-monthly 28-day GPS survey of 50 households in South Australia • Focus groups on participants in GPS panels • Six waves of the odometer panel completed • Two waves of GPS panel completed • Focus Groups completed Using an Odometer and a GPS Panel to Evaluate ...

  10. Odometer Surveys

  11. Odometer Pilots Six waves completed Using an Odometer and a GPS Panel to Evaluate ...

  12. Odometer Panels Response rates were as follows: Overall, similar patterns of recruitment and response in Melbourne and Adelaide Using an Odometer and a GPS Panel to Evaluate ...

  13. Odometer Panels - Response Comparison * These are all TravelSmart households Negligible difference between 3 month and 4 month frequency Using an Odometer and a GPS Panel to Evaluate ...

  14. Odometer Panels – Demographic Bias? The demographic profile of the sample from wave to wave is remarkably stable. There may be some coverage error, which can be corrected by applying weighting factors, but there does not appear to be any systematic non-response error. Using an Odometer and a GPS Panel to Evaluate ...

  15. Odometer Panels – Elapsed Time – SA Using an Odometer and a GPS Panel to Evaluate ...

  16. Odometer Panels – Elapsed Time – Victoria Using an Odometer and a GPS Panel to Evaluate ...

  17. Odometer Panels – Average VKT – SA Using an Odometer and a GPS Panel to Evaluate ...

  18. Odometer Panels – Average VKT –Victoria Strong evidence of success in collecting Odometer readings– not Trip meter readings Using an Odometer and a GPS Panel to Evaluate ...

  19. Odometer Survey - Conclusions • Method works in both a small and large urban area • Response rates are higher than normal for a postal survey • Good evidence for successful reporting of Odometer readings and not trip-meter readings • The sample does not become more biased over time, although rotation of the panel may still be preferable. Using an Odometer and a GPS Panel to Evaluate ...

  20. GPS Surveys

  21. GPS Panel • Set up as 50 households in SA • Two waves conducted with 28-day task, six months apart • Third wave set up with 15-day task, six months later Using an Odometer and a GPS Panel to Evaluate ...

  22. GPS Panels Using an Odometer and a GPS Panel to Evaluate ...

  23. GPS Panels – Days of Data by Person Using an Odometer and a GPS Panel to Evaluate ...

  24. GPS Survey Analysis • Analysis has been done at several levels • Disaggregate – person by day • Aggregated to days of the week • Aggregated to persons • Aggregated further to households • In wave 2, some households overlapped the Easter Holidays • Person days that appeared to have extensive travel on one or two days in the period were dropped from disaggregate analysis Using an Odometer and a GPS Panel to Evaluate ...

  25. GPS Panel – Trip Data Per Person Day * 4 households were found to have undertaken excessive (probably holiday) travel on two or more days around the Easter period in 2006 and were excluded from these statistics Using an Odometer and a GPS Panel to Evaluate ...

  26. GPS Panel – Trip Data Per Person by Day of Week Note that even the large values are included in Wave 2. Using an Odometer and a GPS Panel to Evaluate ...

  27. GPS Panel – Trip Data Per Person by Day of Week Note that even the large values are included in Wave 2. Using an Odometer and a GPS Panel to Evaluate ...

  28. GPS Panels – Trip Data Per Household Using an Odometer and a GPS Panel to Evaluate ...

  29. GPS Duration • Panel Survey suggests that: • Recruitment rates are not affected much between 7 and 28 days • Also, early drop out is not much affected by the length of GPS recording • Statistics tend to stabilise after about 10-12 days • We have determined that there is no halo effect in the first few days • Ideal appears to be a 15-day GPS Using an Odometer and a GPS Panel to Evaluate ...

  30. GPS Frequency • Attrition for three waves of the six-monthly GPS was not markedly different than for two waves of the annual GPS survey • Annual participants have received interim mailings • Non-compliance rate is about double in the annual survey (8% versus under 4%) Using an Odometer and a GPS Panel to Evaluate ...

  31. Focus Groups

  32. Focus Groups - Themes • Six themes were derived from the group discussions: • Respondents’ understanding of the survey task; • The form and functions of the devices; • Patterns of respondent behaviour in undertaking the task; • Reactions to the survey documents and survey administration; • Respondent attitudes and perceptions of issues relevant to the study; and • Curiosities about the study displayed by respondents. Using an Odometer and a GPS Panel to Evaluate ...

  33. Focus Groups - Outcomes • Newsletter- to encourage and educate respondents • Sourcing new devices – to improve performance • Refining survey documentation – to further clarify the GPS task Using an Odometer and a GPS Panel to Evaluate ...

  34. Conclusions • Both panel surveys are feasible methods • Odometer survey can show small differences in average VKT with suitable sample sizes • GPS survey can provide a much greater wealth of data on effects of the policy • Other work shows much smaller sample sizes are required for GPS versus Odometer Using an Odometer and a GPS Panel to Evaluate ...

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