1. Car Ownership Models Meeghat Habibian History and Analysis
Transportation Demand Analysis
Lecture note
Car Ownership Models
History and Analysis
Meeghat Habibian

2. Outline Current situation Stakeholders
Situation in transportation planning
Model types
TRRL model
Betes model
Transportation Demand Analysis- Lecture note
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3. Current situation USA Europe World Iran 1/21
Transportation Demand Analysis- Lecture note
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World
Iran

4. Stakeholders Car manufacturers
Consumer valuation of attributes of cars that are not yet on the market.
Oil companies
Future demand for their products and might benefit
International organizations (e.g., World Bank)
Assist in investment decision-making.
National governments (notably the Ministries of Finance)
Forecasting tax revenues and impact of changes in taxation.
Traffic and environmental departments of regions
Energy consumption, Urban traffic congestion, Forecasting transportation demand, Crash fatalities and air pollution
Transportation Demand Analysis- Lecture note
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5. Situation in Transportation planning
Transportation planning process:
Socio-Economic
and Land Use
O-D Survey
Study Area
Travel Demand Modeling, Trip
Forecasting, Model Validation
Detecting the Existing
Situation (Do Nothing)
Preparing Models
Of Scenarios
Network and
Transit Modeling
Trip Forecasting
And Assignment
Future/Scenarios
Scenarios
Assessment
Land Use
TDM and TSM
Scenario Combination,
Assessment and Final
Suggested Plan
Scenario
Selection
Evaluation Criteria
Definition
Study Area
O-D Survey
Network and
Transit Modeling
Car Ownership
Models
Detecting the Existing
Situation (Do Nothing)
Transportation Demand Analysis- Lecture note
Land Use
Preparing Models
of Scenarios
TDM and TSM
Trip Forecasting
And Assignment
Future/Scenarios
Trip Forecasting
And Assignment
Future/Scenarios
Evaluation Criteria
Definition
Scenarios
Assessment
Scenario
Selection
Scenario Combination,
Assessment and Final
Suggested Plan
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6. Modeling approaches Static vs. Dynamic models
Aggregate vs. Disaggregate Models
Long-term vs. Short-term Models
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7. Model types: 5/21 Car Ownership Models Aggregate Disaggregate
Cohort model
Time Series
model
Car Market
Model
Static disaggregate
models
Static disaggregate
car type choice models
Transportation Demand Analysis- Lecture note
Panel data
models
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8. Transportation Demand Analysis
Lecture note
Aggregate Models

9. Time Series Models Development of car ownership over time
Sigmoid-shape
Button et al. (Button et al., 1993)
Ingram and Liu (1998), double logarithmic specification to explain car and vehicle ownership in many countries and cities across the world.
National Road Traffic Forecasts (NRTF) in the UK (Whelan et al., 2000, Whelan, 2001), aggregate model builds on the earlier UK work in applying a logistic curve for saturation
Dargay and Gately (1999), flexible Gompertz function to predict the motorisation rate (the number of cars per 1,000 persons)
Transportation Demand Analysis- Lecture note
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10. Cohort Models Segment the current population into groups:
Time based cohorts (e.g., 5 year cohorts)
Location based cohorts (e.g., zonal based) …
Van den Broecke (1987) for the Netherlands, combination of a cohort survival model and an econometric model
Madre and Pirotte (1991)
Transportation Demand Analysis- Lecture note
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11. Car Market Models
Same as time series models, but distinguishes between
demand for cars and supply of cars in the car market
Sigmoid-shape
Mogridge (1983),
Cramer and Vos (1985), car ownership depends on car prices, income, the variation of income and the development over time in the utility of using a car
Berry et al (1995), which is a model of the market for new cars only
Transportation Demand Analysis- Lecture note
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12. Transportation Demand Analysis
Lecture note
Disaggregate Models

13. Static Disaggregate Car Ownership Models
Contains discrete choice models that deal with the number of cars owned by a household
Hague Consulting Group (1989), the Dutch national model system (LMS) for transport, binary logit models as follows
Bhat and Pulugurta (1998)
Hague Consulting Group (2000), the car ownership model for Sydney
Transportation Demand Analysis- Lecture note
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14. Static Disaggregate Car Type Choice Models
- This category contains discrete choice models that deal the choice of car type of the household, given car ownership.
Page et al. (2000) for new vehicle purchasing
Birkeland and Jordal-Jørgensen (2001)
Transportation Demand Analysis- Lecture note
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15. Panel Data Car Ownership Models
Reveals the change in travel behavior of individuals
Needs detail individual data
Kitamura (1989)
Hanly (2000)
Woldeamanuel (2009)
Dargay (2007)
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16. *Models Summary 12/21 Transportation Demand Analysis- Lecture note
Aggregate time series model
Cohort models
Aggregate market models
Static disaggregate ownership models
Static disaggregate type choice models
Panel models
Demand-supply
Demand
Supply and demand
Level of aggregation
Aggregate
Disaggregate
Dynamic or static model
Dynamic
Static
Long or short run forecasts
Short, medium and long (saturation)
Medium and long
Short, medium and long
Long
Short and long
Data requirements
Light
Moderate
Heavy
Socio-demographic-impacts
Limited
Many possible
Impact of license holding No
Yes
Possible
Impact of car cost
Fixed and variable
None
Impact of income
Attitudinal variables
Hard to include
Cohort-specific attitudes can be included
Can be included if specific questions in dataset
Transportation Demand Analysis- Lecture note
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17. *Examples of empirical models
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18. (An Aggregate time series model)
Transportation Demand Analysis
Lecture note
The TRRL Models
(An Aggregate time series model)

19. Introduction Transport and Road Research Laboratory, TRRL (UK)
Tanner (1958):
A saturation point (S) exists where car ownership rates (Ct) stabilize
The logistic curve is compatible with the theory of ownership
𝑪 𝒕 = 𝑺 𝟏+ 𝒃 𝒆 − 𝒂 𝑺 𝒕
Transportation Demand Analysis- Lecture note
Ct: Car Ownership at time t
S: Saturation level
t: time
a, b: Model parameters
g: Car ownership growth rate
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20. Assumptions The relation of g and Ct is linear 𝑔=𝛼+𝛽 𝐶 𝑡
developed countries
The relation of g and Ct is linear
𝑔=𝛼+𝛽 𝐶 𝑡
For a developed country:
𝛼>0 𝛽<0
𝑔=0→𝛼+𝛽𝑆=0
→𝑆=− 𝛼 𝛽
Transportation Demand Analysis- Lecture note
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21. Parameters Boundary conditions: Therefore:
At 𝑡=0→ 𝐶 𝑡 = 𝐶 0 → 𝐶 0 = 𝑆 1+𝑏 →𝑏= 𝑆 𝐶 0 −1
At 𝑡=0→𝑔= 𝑔 0 =𝑎 𝐶 0 𝑆− 𝐶 0 →𝑎= 𝑔 0 𝐶 0 𝑆− 𝐶 0
Transportation Demand Analysis – Car Ownership Models
Therefore:
𝐶 𝑡 = 𝑆 1+ 𝑆 𝐶 0 −1 𝑒 𝑔 0 𝐶 0 𝐶 0 −𝑆 𝑆 𝑡

22. Notes The model is presented for developed countries
The pattern may be different for some cities
Different levels of saturation may be occurred for different groups of population
Different levels of saturation may be occurred along time
Recreational vehicles may make noise to this model
Household characteristics are not appeared
Transportation Demand Analysis – Car Ownership Models

23. (A Disaggregate model)
Transportation Demand Analysis
Lecture note
The Bates Model
(A Disaggregate model)

24. Introduction A disaggregate car ownership model
Uses household information (e.g., household income)
derive a probability that a given household will own a number of cars
Transportation Demand Analysis – Car Ownership Models

25. The Model 𝑃 0 1− 𝑃 0 = 𝑎 0 𝐼 − 𝑏 0 𝐷 𝐶 0 𝑃 2 𝑃 1 = 𝑎 1 𝑒 𝑏 1 𝐼𝐷 −𝑐1
𝑃 0 1− 𝑃 0 = 𝑎 0 𝐼 − 𝑏 0 𝐷 𝐶 0
𝑃 2 𝑃 1 = 𝑎 1 𝑒 𝑏 1 𝐼𝐷 −𝑐1
𝑃 0 + 𝑃 1 + 𝑃 2 =1
Pi: the probability that a household will own i car(s)
I: Household Income
D: Density (Number of Households per Hectare)
a, b, c: Parameters of the Model
Transportation Demand Analysis – Car Ownership Models

26. A More Developed Model
P(1+): the probability that a household will own one or more cars with corresponding saturation level, S(1+).
𝑃 = 𝑆( 1 + ) 1+𝑒𝑥𝑝(− 𝑎 𝐼 𝑡 𝑝 𝑡 −𝑏 0 )
P(2+): the probability that a household will own two or more cars with corresponding saturation level, S(2+).
𝑃 = 𝑆( 2 + ) 1+𝑒𝑥𝑝(− 𝑎 2 − 𝑏 2 𝐼 𝑡 𝑝 𝑡 )
𝑃 0 =1−𝑃 1 +
𝑃 1 =𝑃 −𝑃 2 +
𝑃 2 =𝑃( 2 + )
Transportation Demand Analysis – Car Ownership Models
It: Household income in year t
pt: Car price in year t

27. Transportation Demand Analysis- Lecture note
Finish