AITPM presentation

1. Value of Time of Carshare Users in Sydney
Revealed Preference Study of GPS Data
Dr. V.V. Dixit | John Trieu | Sisi Jian | Xun Li

2. Introduction – Why Study Value of Time?
• Economic cost of congestion
– $3.9 billion to Sydney in 2005
(BITRE, 2007)
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3. This Study – Value of Time in Sydney
• Goal
– Value of time for motorists in Sydney
• Why?
– Important consideration in Congestion Charging
schemes
– Important input to Cost-Benefit Analysis of
transport projects
• Economic “benefit” of travel time savings
• How?
– Revealed preference study of GPS data
– Data provided by carshare program in Sydney
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4. Value of Travel Time Savings (1)
• Value of Time
– Not directly measurable
– Minimum travel time, regardless of mode and
route
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5. Value of Travel Time Savings (2)
• Need to consider the “Value of Travel Time
Savings”
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6. What is a Revealed Preference study?
• Collection of raw data (e.g. GPS logs)
• Convert data to trips
• Determine relationships between trip
decisions and factors influencing choices
• The preferences of drivers are “Revealed”
– Preferences are not explicitly “Stated” by drivers
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7. Past Studies
• Different locations = Different characteristics
– Los Angeles
– Brisbane
• Stated Preference = Controlled Experiment
(Hensher, Greene and Li, 2011)
– Artificial environment
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8. Delineating Trips – Overview
• GPS Logs = Data Points
– Need trips
• Trip Identification – Trip Ends
– (1) Time between GPS data points
– (2) Time with zero movement
– (3) Significant changes in direction
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9. Delineating Trips – (1) Time between GPS data points
• Large amount of time (e.g. 2 Days)
– Trip has ended
• Cut-off = 20 minutes
– Timeout of in-car GPS units
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10. Delineating Trips – (2) Time with zero movement
• Based upon maximum signal cycle time in
Sydney
– 150 seconds during peak periods
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11. Delineating Trips – (3) Significant changes in direction
• U-turns
• Turns greater than 90 degrees
– Sensitivity testing undertaken on the
change in heading
– No change in number of trips identified
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12. This Study
• Focal Point
– Toll Road versus Untolled Alternative
– Can isolate value of time
• Explicit cost for toll road
• Stochastic travel time saving
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13. Study Area (1) – M2 vs Epping Road
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14. Study Area (2) – M4 vs Parramatta Road
• Used as a “control” for the study
– Equivalent to “no treatment” scenario in
experiments
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15. This Study
• Other variables / covariates
– Age / Experience
– Preferred Travel Mode
– Car Ownership
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16. Modelling – Value of Expected Travel Time Savings
• Regression Modelling
– Binary Logit Model
Choice of Motorway or Arterial
• Value of Expected Travel Time Savings (VETTS)
– $9.63 / hour
• Comparison VETTS
– Los Angeles, USA: $21.46 / hour
– Brisbane, Australia: $17.60 / hour
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17. Modelling – Value of Expected Travel Time Savings
• Value of Expected Travel Time Savings (VETTS)
– $9.63 / hour
• VETTS result is more than 50% less than in
other cities
• Reason for difference
– VETTS identified is specific to Carshare Users
– Carshare Users are suspected of having lower
VETTS compared to average motorist
• Cannot be used as a representative sample group
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18. Further Studies
• Risk aversion
– Travel times are stochastic
– Need to include risk parameter
• Model including risk parameter is ongoing
– Risk models considered:
• Constant Absolute Risk Aversion (CARA)
• Constant Relative Risk Aversion (CRRA)
• Ongoing / Not yet finalised
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19. Questions?
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