The importance of value of time studies a dutch perspective

The 2013 national Dutch value of time study
Gerard de Jong – Significance and ITS Leeds

29 October 2015


and reliability
The 2013 national Dutch value of time study
Gerard de Jong – Significance and ITS Leeds

29 October 2015


Contents
1. What’s the question?
2. Data collection:

I.
II.

The 2009 SP data: internet panel
The 2011 SP data: en-route recruitment

3. Model estimation
4. Impact of recruitment method
5. The recommended values
6. A fair comparison of the 1997 and 2009/2011 VTT
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Why do we need a VTT?

 In many countries, transport projects (e.g. new road or railway line) are
evaluated ex ante using cost-benefit analysis (CBA)
 In CBA project effects are expressed in money units
 Costs include construction, maintenance and external cost
 Main benefit often is travel time saved

□

There could also be journey time reliability benefits (often still ignored)

 This is in hours or minutes, so we need a conversion factor to money

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This factor is called the value of travel time VTT (e.g. in euros per hour)

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The context: CBA of transport projects
Costs

Benefits

Construction costs

Time benefits: Pt*Qt
Pt: Value of travel time VTT
Qt: from transport model

Change in maintenance
costs

Reliability benefits: Pr*Qr

Change in external costs

Other transport cost savings

Pr: Value of travel time variability VTTV
Qr: forecasting model or surcharge

From transport model

…

…

…

…
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The new national study
 The objective of this project, for the Dutch Ministry of Infrastructure and the
Environment, was:
to provide values of time (update) and travel time reliability (first Dutch empiricallybased values) for passenger and freight transport by mode that can be used in costbenefit analysis (CBA) of transport projects

 The project was completed and the report was officially released in June 2013)

(weblink at the end); the values are now official: used in all national transport
projects
 In The Netherlands the VTT and VTTV are specifically for use in CBA, not for
inputs into transport forecasting models
 The Netherlands also had national VTT studies (passengers) in 1988-1990 and
1997-1998

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What’s the question?
 This presentation is about the passenger transport component of the study
 Values of time (VTTS) in passenger transport nowadays mainly come from
Stated Preference (SP) surveys
(see international meta-analysis by Wardman et al., 2012)

 Different interview methods:

□
□
□
□

Mailback (pen and paper/cards)
CAPI (used for freight transport)
CATI
Internet
Recruitment method:
− Project-specific recruitment (e.g. en-route)
− From existing internet panel

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Initial choice of interview and recruitment
method (2009 data)
 The SP surveys required considerable customisation

□

Mailback can only provide this through extensive two-step procedures

 CAPI and CATI were considered too expensive for a large survey (labour
cost)
 Initial choice: internet survey using an existing internet panel

8


2009 survey procedure (1)
 5,760 members of an existing on-line panel were interviewed using
computerised stated preference interviews in November 2009
 Specific target numbers of interviews were set (and reached) for different
segments:

□
□
□
□

Transport mode used (car, train/metro, bus/tram, airplane and recreational
navigation)
Travel purpose (commuting, business, other)
Time-of-day (peak, off-peak)
Presence of transfers (public transport only)

 All respondents were asked which modes they had used in the past three
months, etc.

□

This was used to allocate respondents to questionnaires for specific segments

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2009 survey procedure (2)
 All respondents were drawn from the largest on-line panel of The
Netherlands (240.000 participants)
 The survey could be started by clicking on a weblink
 The members received a reward for successfully completing the interview
(equivalent to €1.50)
 The interviews on average took 20 minutes

10


Example of an SP choice screen (exp. 1)

11

Example of an SP choice screen (exp. 2a)

12


Initial results (2009 data)
 VOTs implausibly low

□
□

About € 4 per hour for car and public transport
Substantially lower than the official values (about € 9 per hour) and the
international literature

 Checked for possible explanations:

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□
□
□
□
□
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socio-economic composition of sample
travel time distribution of sample
changes in the statistical design of the SP

Including reliability in the SP
Increased use of mobile phones, smartphones
Impact of economic crisis
Increase in congestion

 These only explained part of the differences with the official values

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But there could be another explanation …
 The sample of respondents obtained from this internet panel might be
biased with respect to their value of time
 Within each segment (socio-economic, trip purpose, trip length, mode),
the respondents that participate in such an online panel (which takes time,
for a rather low monetary reward) might have a lower VOT than a nonparticipant
 This is a self-selection problem
 Even after expansion, the resulting values of time would then be lower
than the true values of time
 To investigate this hypothesis, another data set was collected in the first
half of 2011
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The 2011 SP data: en-route recruitment
 Almost 1500 respondents recruited at petrol stations, parking garages,
train stations, bus stops, airports and ports
 This is the same recruitment method as in earlier national value of time
surveys of 1988/1990 and 1997/1998
 Persons willing to participate were asked to answer an internet

questionnaire on the intercepted trip:

□
□

Almost identical to the questionnaire used in 2009
We only asked one additional question to determine whether they were a
member of an internet panel (and whether this was “our” internet panel)

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2011 Models distinguishing members/nonmembers of internet panels
 MNL models
 Advanced MNL models that:

□
□

yield a higher VTT for higher base time and cost levels, and
smaller VTTs for smaller changes offered in time and cost

 Advanced MNL with socio-economic interaction terms
 Advanced MNL with socio-economic interaction terms plus latent VTT
classes (LC model)

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Linear versus non-linear time and cost

effects in the utility function
Utility function 1997:

Utility function 2009/2011:

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4. Results for MNL model
Mode

Purpose

Relative VTT for panel member
(non-member=1)
MNL

Commuting

0.61

Business

0.93

Other

0.90

Airplane

All

1.07

Recr. navigation

Other

(0.96)

Car/train/BTM

Adv MNL

Adv MNL +
socio

Latent
class

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4. Results for MNL models
Mode

Purpose

Relative VTT for panel member

(non-member=1)
MNL

Advanced
MNL

Commuting

0.61

0.80

Business

0.93

0.88

Other

0.90

0.93

Airplane

All

1.07

0.82

Recr. navigation

Other

(0.96)

(0.98)

Car/train/BTM

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4. Results for MNL models
Mode

Purpose

Relative VTT for panel member
(non-member=1)
MNL

Advanced
MNL

Adv.MNL w.
interaction

Commuting

0.61

0.80

0.80

Business

0.93

0.88

0.87

Other

0.90

0.93

(1.01)

Airplane

All

1.07

0.82

0.82

Recr. navigation

Other

(0.96)

(0.98)

(0.98)

Car/train/BTM

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4. Results for MNL and LC models
Mode

Purpose

Relative VTT for panel member
(non-member=1)
MNL

Advanced
MNL

Adv.MNL w.
interaction

Latent
class

Commuting

0.61

0.80

0.80

0.80

Business

0.93

0.88

0.87

(0.81)

Other

0.90

0.93

(1.01)

(0.89)

Airplane

All

1.07

0.82

0.82

0.82

Recr. navigation

Other

(0.96)

(0.98)

(0.98)

(0.95)

Car/train/BTM

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4. Results for panel members 2009 and 2011

Mode

Purpose

Relative VTT for panel member
(non-member=1)
Advanced MNL 2009
(‘our’ panel)

Advanced MNL
2011 (all panels)

Commuting

0.64

0.80

Business

0.66

0.88

Other

0.74

0.93

Airplane

All

0.70

0.82

Recr. navigation

Other

(1.06)

(0.98)

Car/train/BTM

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Discussion of results: does it matter/help? (1)

 Especially for commuting (car, train, bus, tram, metro): significant lower
values for panel members,

□

even after correcting for the different distributions for the travel time and travel
cost, and after inclusion of the socio-economic interactions

 Similar findings for the business and for airplane segment
 Other purposes and recreational navigation: no significant difference
between panel and non-panel
 We conclude that in the 2009 survey there was a bias towards low-VTT
persons, who are willing to give up time to participate in an internet panel
and to fill out web questionnaires for a rather small reward

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Discussion of results: does it matter/help? (2)
 The resulting VTTs from the 2011 survey are much more in line with the
values found in 1988/1990 and 1997/1998,

□
□

which have always been regarded as very plausible by the various transport
sectors,
and are not considered to be particularly high in an international perspective

 Our conclusion is that the most likely explanation is that the 2011 values

are correct and that the 2009 values are biased downwards

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The final VTT results are based on a
combination of the 2009 and 2011 data
 The base VTT and VTTV levels come from estimates on the 2011 data
 Socio-economic interaction effects and the effect of the base time and
cost levels as well as of changes in time and cost offered in the SP are
estimated on 2009 and 2011
 Also: latent class models used here, and expansion of the estimation
results to the population (in hours travelled) using the 2010 national travel
survey (OViN)
 This yields the recommended values for use in CBA

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