Download - INTEGRATED CHOICE AND LATENT VARIABLE MODELS
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Aurélie Glerum, EPFL
INTEGRATED CHOICE AND LATENT VARIABLE MODELS
APPLICATIONS TO VEHICLE AND MODE CHOICE
MODELING
IRE seminar, USI
10th October 2013
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Aurélie Glerum Lidija Stankovikj
Michaël Thémans Michel Bierlaire
A HYBRID CHOICE MODEL TO FORECAST THE DEMAND FOR ELECTRIC VEHICLES
FROM SURVEY DESIGN TO MODEL APPLICATION
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Introduction & motivation Data collection Methodology Model • SP model • Choice model for forecasting Forecasting analysis Conclusion
OUTLINE 3
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Aim • Develop a comprehensive methodology to forecast demand for a
new technology: electric vehicles
Context • Current situation:
• Alternative fuel vehicles (LPG, CNG, etc.) on the car market • Electric vehicles (EV) being released
• Collaborative project EPFL-Renault Suisse: • Renault has launched Zero Emission (Z.E.) product line in 2011-2013 • Aim: analyze demand for two EV models for private use
4 INTRODUCTION & MOTIVATION
Zoé Fluence Z.E.
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Literature • SP survey design:
• Personalized choice situations (Bunch et al., 1993, Achtnicht et al., 2008, etc.) • Fractional factorial designs (Brownstone et al., 1996, Ewing and Sarigöllü, 2000,
Horne et al., 2005)
• Choice models for demand for EVs or alternative-fuel vehicles: • Widely applied (Brownstone and Train, 1999, Dagsvik et al., 2002, Mueller and de
Haan, 2009, etc.) • Integrated choice and latent variable (ICLV) models for environmental
concern (Alvarez-Daziano and Bolduc, 2009)
• Model application:
• Models developed on SP data need adjustments before application (Brownstone et al., 1996)
• Joint RP-SP estimations (e.g. Brownstone et al., 2000) • Lack of examples of applications of models designed to evaluate
demand for new alternatives (Daly and Rohr, 1998)
5 INTRODUCTION & MOTIVATION
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Main features of the model • Customized choice situations using iterative proportional fitting (IPF)
• Include attitudinal dimensions
• Specify model for the whole market, from a model based on SP data
6 INTRODUCTION & MOTIVATION
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Main features of the model • Customized choice situations using iterative proportional fitting (IPF)
• Include attitudinal dimensions
• Specify model for the whole market, from a model based on SP data
7 INTRODUCTION & MOTIVATION
COMPREHENSIVE FRAMEWORK
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Type of survey: stated preference (SP) survey Within same car segment: hypothetical choices between
Own car Renault – gasoline (if own car is not Renault) Renault – electric
8 DATA COLLECTION
Choice
Gasoline / diesel
New alternative: Electric
Competitors Renault
Renault
Choice
Gasoline / diesel
New alternative: Electric
Renault
Renault
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9 DATA COLLECTION
2 phases: Phase I:
Characteristics of respondent’s car(s) Socio-economic information Mobility habits
Phase II: Choice situations Opinions on topics related to EV Perceptions of four categories of vehicles
STRUCTURE OF THE SURVEY
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DATA COLLECTION
2 phases: Phase I:
Characteristics of respondent’s car(s) Socio-economic information Mobility habits
Phase II: Choice situations Opinions on topics related to EV Perceptions of four categories of vehicles
STRUCTURE OF THE SURVEY
…used to design…
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DATA COLLECTION
Opinions on themes related to electric vehicles • Environmental concern (5 statements)
Example: An electric car is a 100% ecological solution. • Attitude towards new technologies (5 statements)
Example: A control screen is essential in my use of a car. • Perception of the reliability of an electric vehicle (5 statements)
Example: Electric cars are not as secure as gasoline cars. • Perception of leasing (5 statements)
Example: Leasing is an optimal contract which allows me to change car frequently. • Attitude towards design (5 statements)
Example: Design is a secondary element when purchasing a car, which is above all a practical transport mode.
Ratings • Total disagreement (1) • Disagreement (2) • Neutral opinion (3) • Agreement (4) • Total agreement (5) • I don’t know (6)
STRUCTURE OF THE SURVEY
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DATA COLLECTION
5 types of respondents sampled in Switzerland: • Recent buyers • Prospective buyers • Renault customers • Pre-orders • Newsletter
SAMPLE
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DATA COLLECTION
5 types of respondents sampled in Switzerland: • Recent buyers • Prospective buyers • Renault customers • Pre-orders • Newsletter Sampling protocol representativity from: • 3 language regions of Switzerland (German, French, Italian) • Gender • Age category (18-35 years, 36-55 years, 56-74 years)
SAMPLE
Sampling protocol
All available
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DATA COLLECTION 14
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DATA COLLECTION
An example of choice experiment
Reported by respondent
EXPERIMENTAL DESIGN
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16 DATA COLLECTION
An example of choice experiment
Deduced from segment of owned car
EXPERIMENTAL DESIGN
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17 DATA COLLECTION
An example of choice experiment
Obtained from data base of cars currently sold on market
EXPERIMENTAL DESIGN
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18 DATA COLLECTION
An example of choice experiment
Fixed attributes
EXPERIMENTAL DESIGN
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19 DATA COLLECTION
An example of choice experiment
Design variables
EXPERIMENTAL DESIGN
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DATA COLLECTION EXPERIMENTAL DESIGN
Design variables
EV variable Level 1 Level 2 Level 3 Level 4
Purchase price (Pown + 5’000) * 0.8 (Pown+ 5’000) * 1 (Pown + 5’000) * 1.2 -
Governmental incentive
- 0 CHF - 500 CHF - 1’000 CHF - 5’000 CHF
Cost of fuel/electricity for 100 km
1.70 CHF 3.55 CHF 5.40 CHF -
Battery lease 85 CHF 105 CHF 125 CHF -
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21 DATA COLLECTION EXPERIMENTAL DESIGN
Fractional factorial design with sampling weights Fractional factorial design
● Orthogonal ● Size = 64 (full factorial design has
size 108)
Sampling weights:
● Correct for oversampling of some levels
● Weights computed with iterative proportional fitting (IPF)
Incentive Price Fuel cost of 100 km Battery lease
1 0 0.80 1.70 85
2 0 1.00 3.55 125
3 0 1.00 5.40 105
4 0 1.20 3.55 105
5 -500 0.80 1.70 125
6 -500 1.00 3.55 85
7 -500 1.00 5.40 105
8 -500 1.20 3.55 105
9 -1000 0.80 3.55 105
10 -1000 1.00 5.40 105
11 -1000 1.00 3.55 85
12 -1000 1.20 1.70 125
13 -5000 0.80 3.55 105
14 -5000 1.00 5.40 105
15 -5000 1.00 3.55 125
16 -5000 1.20 1.70 85
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Figure extracted from Walker and Ben-Akiva, 2002.
METHODOLOGY 22
Hybrid choice model (HCM): DCM with latent constructs. Allows to capture e.g. attitudes et perceptions
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Figure extracted from Walker and Ben-Akiva, 2002.
METHODOLOGY 23
Hybrid choice model (HCM): DCM with latent constructs. In this research: focus on the integration of choice model and latent variable model (ICLV)
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Hybrid choice model specification Structural equations: Choice model: with Latent variable model: with Measurement equations (continuous): with
METHODOLOGY 24
inninin XXVU εβ += );,( *
),0(~ ωσω Nnninn XhX ωλ += );(*
)1,0(~ EVinε
nnn XmI υα += );( ** ),0(~ υσυ Nn
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SP MODEL 25
Battery leasing cost
Governmental incentive
Fuel/electricity costs
Car purchase price
Utility
Renault – electric (RE)
Explanatory variables
Competitors – gasoline (CG)
Renault – gasoline (RG)
Choice
Household composition Frequent use of PT
High income Age
Number of cars
Target group (customer type)
Language region
Pro-convenience attitude
The design of a car is secondary, the car is above all practical.
The spaciousness of car is more important than its look.
I prefer having a car with a new propulsion technology than a car with a nice look.
Gender
Household size
Age > 45 years
Retired
Home owner
Pro-leasing attitude
Indicators
Allows to change car frequently.
Presence of children
30 years < age < 50 years
Family situation
Retired
Smartphone
Explanatory variables
Language region
High education degree Income
Feeling that car does not belong completely to oneself.
Dislikes allowing a leasing budget every month. Leasing is more adapted in the case of the purchase of an EV. Leasing is particularly adapted in the case of the purchase of an electric vehicle.
Explanatory variables
Indicators
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SP MODEL 26
Battery leasing cost
Governmental incentive
Fuel/electricity costs
Car purchase price
Utility
Renault – electric (RE)
Explanatory variables
Competitors – gasoline (CG)
Renault – gasoline (RG)
Choice
Household composition Frequent use of PT
High income Age
Number of cars
Target group (customer type)
Language region
Pro-convenience attitude
The design of a car is secondary, the car is above all practical.
The spaciousness of car is more important than its look.
I prefer having a car with a new propulsion technology than a car with a nice look.
Gender
Household size
Age > 45 years
Retired
Home owner
Pro-leasing attitude
Indicators
Allows to change car frequently.
Presence of children
30 years < age < 50 years
Family situation
Retired
Smartphone
Explanatory variables
Language region
High education degree Income
Feeling that car does not belong completely to oneself.
Dislikes allowing a leasing budget every month. Leasing is more adapted in the case of the purchase of an EV. Leasing is particularly adapted in the case of the purchase of an electric vehicle.
Explanatory variables
Indicators
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Structural equations: Choice model: Latent variable model: 𝐴𝐴𝐴𝐴 = 𝛽𝑀𝑀𝑀𝑀𝑀 + ∑ 𝛽𝑀,𝑖 ⋅ 𝑋𝑀,𝑖 + exp 𝜈𝑀 ⋅ Ω𝑀𝑖 with Ω𝑀 ∼ 𝑁(0,1) 𝐴𝐴𝐴𝐴 = 𝛽𝑀𝑀𝑀𝑀𝑀 + ∑ 𝛽𝑀,𝑖 ⋅ 𝑋𝑀,𝑖 + exp 𝜈𝑀 ⋅ Ω𝑀𝑖 with Ω𝑀 ∼ 𝑁(0,1) Measurement equations (continuous): 𝐼𝑀,𝑘 = 𝛼𝑀,𝑘 + 𝜆𝑀,𝑘 ⋅ 𝐴𝐴𝐴𝐴 + exp 𝜎𝑀,𝑘 Ω𝑀,𝑘 with Ω𝑀,𝑘 ∼ 𝑁(0,1), for 𝑘 = 1, … , 5 𝐼𝑀,𝑘 = 𝛼𝑀,𝑘 + 𝜆𝑀,𝑘 ⋅ 𝐴𝐴𝐴𝐴 + exp 𝜎𝑀,𝑘 Ω𝑀,𝑘 with Ω𝑀,𝑘 ∼ 𝑁 0,1 , for 𝑘 = 1,2,3
SP MODEL 27
nCGk
kkCGAttCpriceCG XpriceAttCUCG ,)exp( εβββ +++−= ∑
)1,0(~with EVinε
SPECIFICATION
nRGl
llRGAttCpricepriceRG XpriceAttCTGTGUTGRGTGRG ,)31245exp(
3,1245,εββββ ++++−= ∑
REAttCpricepricepriceRE priceAttCTGTGTGUTGRGTGRGTGRE
)45312exp(45,3,12,
ββββ +++−=
nREm
mmAttLBattery XBatteryAttL ,)exp( εβββ +++− ∑
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SP MODEL 28
ESTIMATION RESULTS
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SP MODEL 29
ESTIMATION RESULTS
• 𝛽𝐴𝐴𝐴𝐴 < 0 and significant: pro-convenience individuals less price-sensitive
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SP MODEL 30
ESTIMATION RESULTS
• 𝛽𝐴𝐴𝐴𝐴 < 0 and significant: pro-convenience individuals less price-sensitive
• 𝛽𝐴𝐴𝐴𝐴 < 0 and significant: pro-leasing individuals less affected by changes in battery
leasing price
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Histogram of choice probabilities predicted by MNL and ICLV (80%/20%)
SP MODEL 31
VALIDATION
ICLV
MNL
Value
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Histogram of choice probabilities predicted by MNL and ICLV (80%/20%)
SP MODEL 32
VALIDATION
ICLV
MNL
Value
56.7% 1.7%
29.7% 56.7%
30.2%
1.7%
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Histogram of choice probabilities predicted by MNL and ICLV (80%/20%)
SP MODEL 33
VALIDATION
ICLV
MNL
Lower bound
Upper bound
Value
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Histogram of choice probabilities predicted by MNL and ICLV (80%/20%)
SP MODEL 34
VALIDATION
ICLV
MNL
Lower bound
Upper bound
Value
Difference between average confidence bounds
18.5%
17.3%
44.0% 61.3%
43.4% 61.9% <
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CHOICE MODEL FOR FORECASTING 35
Several corrections to the SP model are needed before the model can be applied for scenario forecasting:
1. Introduction of an aggregate alternative for car models from competitors (using logsum)
2. Correction of constants:
• Current ratio of market shares between Renault and competitors is preserved.
• Estimate potential market share of EV using acceptance rate and Swiss market data.
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CHOICE MODEL FOR FORECASTING 36
Two possible choice situations
Issue: • Choice is supposed to represent all possible alternatives for decision maker • Not the case for owners of Renault cars Solution: • Impute aggregate alternative of gasoline – competitors for these individuals
Choice
Gasoline / diesel
New alternative: Electric
Competitors Renault
Renault
Choice
Gasoline / diesel
New alternative: Electric
Renault
Renault
1. AGGREGATE ALTERNATIVE
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CHOICE MODEL FOR FORECASTING 37
Aggregate alternative imputed for Competitors – Gasoline (CG) Generated from prices & operating costs of new cars on market (matching segment of 2 other alternatives in choice situation)
∑∈
=Ll
CG UV lnexplog
∑∈
⋅⋅+−⋅+=n
CGSs
lnAttCpricessCG priceAttCxASCU )exp(ln βββ
1. AGGREGATE ALTERNATIVE
ln)12100(100 εβ +≤⋅⋅+ llolineUseCostGas CostCost
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CHOICE MODEL FOR FORECASTING 38
Idea: Use: • Market data of current alternatives • SP survey data
2. CORRECTIONS OF CONSTANTS
To estimate possible share for new alternative
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CHOICE MODEL FOR FORECASTING 39
Idea: Use: • Market data of current alternatives • SP survey data Evaluation of potential market share (MS) for EV
2. CORRECTIONS OF CONSTANTS
To estimate possible share for new alternative
%27%6RG) Owns|RE (Choice%%94CG) Owns|RE (Choice%)RE(
=⋅+⋅=MS
Market share of competitors
Market share of Renault
Acceptance rate EV in the questionnaire for CG owners (weighted)
Acceptance rate EV in the questionnaire for RG owners (weighted)
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FORECASTING ANALYSIS 40
Example of scenario
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CONCLUSION 41
Conclusions
• Operational model obtained by the presented procedure: from data collection to model application
• Important to include market data when forecast for a new alternative Future analyses • Analyzed the demand for EV for private use, but alternative uses
exist (e.g. car sharing) • Now that EVs are more present on the market, revealed preferences
(RP) data can be collected and the model can integrate both.
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Aurélie Glerum Bilge Atasoy
Michel Bierlaire
USING ADJECTIVES TO MEASURE PERCEPTIONS IN HYBRID CHOICE MODELS
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Introduction & motivation The data Model specification Estimation results Validation Conclusion
OUTLINE 43
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INTRODUCTION & MOTIVATION 44
Issues related to the integration of latent variables into choice models:
1. Measurement of latent variable
How to obtain the most realistic and accurate measure of a
perception?
2. Integration of the measurement into the choice model
How to incorporate this information in the choice modeling framework?
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INTRODUCTION & MOTIVATION 45
1. Measurement of latent variable:
• Use of opinion statements Five-point Likert scale
• Recent technique developed in social sciences:
Respondents report adjectives characterizing a variable of interest (Kaufmann et al., 2001; Kaufmann et al., 2010)
Reflects spontaneous perceptions of individuals (≠ survey designer’s conception of the perception)
Usual way in literature (Likert, 1932; Bearden and Netemeyer, 1999)
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INTRODUCTION & MOTIVATION 46
1. Measurement of latent variable:
• Use of opinion statements Five-point Likert scale
• Recent technique developed in social sciences:
Respondents report adjectives characterizing a variable of interest (Kaufmann et al., 2001; Kaufmann et al., 2010)
Reflects spontaneous perceptions of individuals (≠ survey designer’s conception of the perception)
Usual way in literature (Likert, 1932; Bearden and Netemeyer, 1999)
1ST AIM OF THIS RESEARCH: USE THE ADJECTIVES TO MEASURE PERCEPTIONS
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INTRODUCTION & MOTIVATION 47
2. Integration of the measurement into the choice model:
• Structural equation model (SEM) framework used to characterize latent variable and relate it to its measurement indicators
(e.g. Bollen, 1989).
• Latent variable model embedded into DCM HCM framework • Integration of measurements into HCM framework:
• Well-established for models with opinion statements
• Adjectives need to be quantified
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INTRODUCTION & MOTIVATION 48
2. Integration of the measurement into the choice model:
• Structural equation model (SEM) framework used to characterize latent variable and relate it to its measurement indicators
(e.g. Bollen, 1989).
• Latent variable model embedded into DCM HCM framework • Integration of measurements into HCM framework:
• Well-established for models with opinion statements
• Adjectives need to be quantified
2ND AIM OF THIS RESEARCH: QUANTIFY THE ADJECTIVES TO INTEGRATE THEM IN AN HCM
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THE DATA 49
Two surveys:
• Revealed preferences (RP) survey
• Survey with evaluators (adjective quantification survey)
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THE DATA 50
RP survey • Mode choice study
• Conducted between 2009-2010 in low-density
areas of Switzerland
• Conducted with PostBus (major bus company in Switzerland, operates in low-density areas)
• Info on all trips performed by inhabitants in one day:
• Transport mode • Trip duration • Cost of trip • Activity at destination • Etc.
• 1763 valid questionnaires collected
Choice
RP SURVEY
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THE DATA 51
Adjective data for perception of transport modes: For each of the following transport modes, give three adjectives that describe them best according to you.
Adjective 1 Adjective 2 Adjective 3
1 The car is:
2 The train is:
3 The bus, the metro and the tram are:
4 The post bus is:
5 The bicycle is:
6 The walk is:
RP SURVEY
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THE DATA 52
Adjective data for perception of transport modes: For each of the following transport modes, give three adjectives that describe them best according to you.
Adjective 1 Adjective 2 Adjective 3
1 The car is: convenient comfortable expensive
2 The train is: relaxing punctual restful
3 The bus, the metro and the tram are: fast frequent cheap
4 The post bus is: punctual comfortable cheap
5 The bicycle is: stimulating convenient cheap
6 The walk is: healthy relaxing independent
RP SURVEY
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THE DATA 53
Extraction of information on perceptions 1. Classification into themes:
• Perception of cost • Perception of time • Difficulty of access • Flexibility • Comfort, etc.
2. Focused on adjectives related to one theme
only and one mode only: Comfort in public transportation (PT)
Comfort hardly full packed bumpy comfortable hard irritating tiring unsuitable with bags uncomfortable bad air …
RP SURVEY
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THE DATA 54
Extraction of information on perceptions 1. Classification into themes:
• Perception of cost • Perception of time • Difficulty of access • Flexibility • Comfort, etc.
2. Focused on adjectives related to one theme
only and one mode only: Comfort in public transportation (PT)
Comfort hardly full packed bumpy comfortable hard irritating tiring unsuitable with bags uncomfortable bad air …
RP SURVEY
LATENT VARIABLE WE STUDY
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THE DATA 55
• Asked 25 external evaluators to rate the adjectives on scale of comfort.
• Discrete scale: ratings from -2 to 2.
ADJECTIVE QUANTIFICATION SURVEY
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THE DATA 56
Aims: • Use adjectives to measure perceptions • Quantify them to integrate them into the HCM framework
Now: Ratings from 25 different evaluators
How reliable is each set of ratings? Next step: • Estimate an HCM for each set of ratings (i.e. for each evaluator)
• LV is perception of comfort in PT • LV measured by ratings of one evaluator
• Compare the fit & prediction capabilities of each model
ADJECTIVE QUANTIFICATION SURVEY
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THE DATA 57
… … … … … …
ADJECTIVE QUANTIFICATION SURVEY
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THE DATA 58
… … … … … …
Smallest Euclidean distance to other evaluators
ADJECTIVE QUANTIFICATION SURVEY
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THE DATA 59
… … … … … …
Furthest away from central evaluator
ADJECTIVE QUANTIFICATION SURVEY
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MODEL SPECIFICATION 60
French/German part
Work related trips
Travel Time
Travel Cost
Utility
Soft modes
Explanatory variables
Public transports (PT)
Car
Choice
Perception of comfort in PT
Full-/Part-time job
French/German part
+ 2 cars
Explanatory variables
Distance Age < 50 years
Adjectives describing train 1 Adjectives describing train 2
Adjectives describing train 3
Adjectives describing post bus1 Adjectives describing post bus 2
Adjectives describing post bus 3
Adjectives describing bus 1 Adjectives describing bus 2
Adjectives describing bus 3
Indicators
Figure based on Walker and Ben-Akiva, 2002.
Hybrid choice model
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MODEL SPECIFICATION 61
French/German part
Work related trips
Travel Time
Travel Cost
Utility
Soft modes
Explanatory variables
Public transports (PT)
Car
Choice
Perception of comfort in PT
Full-/Part-time job
French/German part
+ 2 cars
Explanatory variables
Distance Age < 50 years
Adjectives describing train 1 Adjectives describing train 2
Adjectives describing train 3
Adjectives describing post bus1 Adjectives describing post bus 2
Adjectives describing post bus 3
Adjectives describing bus 1 Adjectives describing bus 2
Adjectives describing bus 3
Indicators
Figure based on Walker and Ben-Akiva, 2002.
Hybrid choice model
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ESTIMATION RESULTS 62
• Model estimated for each evaluator ( 25 models estimated)
• Fit indices (for the choice model):
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ESTIMATION RESULTS 63
𝛽𝑐𝑐𝑐𝑐𝑐𝑐𝐴 > 0: A high perception of comfort of PT increases its utility.
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ESTIMATION RESULTS 64
𝛽𝑐𝑐𝑐𝑐𝑐𝑐𝐴 > 0 and 𝛽𝐴𝑖𝑐𝑀𝑃𝑃 < 0: Travel time sensitivity decrease with an increased perception of comfort of PT.
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VALIDATION 65
Estimation on 80% data / Application on 20 % data Fit indices:
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VALIDATION 66
Estimation on 80% data / Application on 20 % data Fit indices: • Fit similar across evaluators • Slightly lower for outlying evaluator
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VALIDATION 67
Analysis of demand indicators across evaluators Example: computation of market shares
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VALIDATION 68
Analysis of demand indicators across evaluators Example: computation of market shares
Disaggregate indicators Probabilities to choose each mode.
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VALIDATION 69
Analysis of demand indicators across evaluators Example: computation of market shares
Aggregate indicators market shares for each mode.
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VALIDATION 70
Analysis of demand indicators across evaluators Example: computation of market shares
Aggregate indicators have lower standard deviations than disaggregate indicators more consistency at aggregate level.
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VALIDATION 71
Analysis of demand indicators across evaluators
High Medium
Low All observations
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CONCLUSION 72
Conclusions:
• Adjectives: alternative way to measure perceptions • Propose a methodology to rate adjectives in order to minimize
subjectivity • Method is robust with respect to poor evaluators
Further improvements: • Two surveys in one step • Comparative approach between classical opinion questions and
adjectives • Comparison between adjective rating on a discrete (-2 to 2) and
continuous scale (-1000 and 1000) • Investigate the effect of other themes (than comfort in PT)
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Thank you!
73