The importance of value of time studies a dutch perspective

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 fi

The 2013 national Dutch value of time study

The 2013 national Dutch value of time study 29 October 2015

and reliability

1 What’s the question?

2 Data collection:

I. The 2009 SP data: internet panel

II. The 2011 SP data: en-route recruitment

3 Model estimation

4 Impact of recruitment method

5 The recommended values

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

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

The context: CBA of transport projects

Pt: Value of travel time VTT Qt: from transport modelChange in maintenance

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

Change in external costs Other transport cost savings

From transport model

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

empirically-based values) for passenger and freight transport by mode that can be used in

cost-benefit 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

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)

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

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

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

Example of an SP choice screen (exp 1)

Example of an SP choice screen (exp 2a)

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:

□ 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

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 non-

participant

 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

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)

2011 Models distinguishing

members/non-members 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)

Linear versus non-linear time and cost

effects in the utility function

Utility function 1997:

Utility function 2009/2011:

4 Results for MNL model

4 Results for MNL models

4 Results for MNL models

4 Results for MNL and LC models

4 Results for panel members 2009 and 2011

Relative VTT for panel member

(non-member=1)

Advanced MNL 2009 (‘our’ panel)

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

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

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

Recommended VTTs in euros per person per hour

  Car Train tram,  Bus, 

metro

All  surface  modes

Recommended reliability ratios

 Reliability ratio (RR) = value of standard deviation of travel time/VTT

 Car, train, bus, tram and metro:

It’s just not fair!

It’s just not fair!

 Fair comparison: comparing like with like

The seven differences (methodological)

Estimation space Interactions with cost and time Interactions with VTT

Cost and time terms Linear Linear & non-linear

Dependence of VTT

on travel time itself No Yes

Socio-economic

interaction factors No education including educationDifferent set,

Expansion procedure Weights per segment Sample enumeration

Expansion totals OVG 1995 OViN 2010

Type of model MNL panel latent class

 Therefore the VTT in the 1998 report and the 2013 report cannot be

compared

 More congestion, more crowded trains, lower compensation of cost, crisis

 New ICT has become much more common in this period:

□ Mobiles (including handsfree, car kit), smartphones, iPads, laptops

□ Easier to use travel time in a more productive/enjoyable way

-> VTT ↓

 In the period 1988-1997 VTT did not change much:

□ Gunn (2001): effect of real income growth more or less balanced by the

Methodology to obtain a fair comparison

 Applying the 1997 methods on the 2009/2011 data is not so interesting (no benefits from methodological improvements)

 So we redid the analysis of the 1997 data using the 2009/2011 methods

 We did this re-analysis step-by-step to see the impact of each of the seven differences (similar steps for the analysis of 2009/2011 data)

 This gives two results:

□ Which VTT would we have obtained in the nineties if we could had used modern methods (and future population data)?

□ The real evolution of VTT by mode and purpose between 1997 and 2009/2011

Detailed comparison for commute

Outcomes: impact of methodological

differences on 1997 or 2009/2011 VTT

Estimation space Interactions with cost and time Interactions with VTT −4%

Cost and time terms Linear Linear & non-linear 0%

procedure Weights per segment Sample enumeration +4% Differs by mode

Expansion totals OVG 1995 OViN 2010 0% Differs by mode

Type of model MNL panel latent class

Outcomes: impact of methodological

differences on 1997 or 2009/2011 VTT

Estimation space Interactions with cost and time Interactions with VTT −4%

Cost and time terms Linear Linear & non-linear 0%

Expansion

procedure Weights per segment Sample enumeration +4% Differs by mode

Expansion totals OVG 1995 OViN 2010 0% Differs by mode

General

Fair comparison 1997 – 2010 (no inflation

correction; comparison of p-LC models)

Bus, tram, metro

All surface modes

Discussion of results of the comparison

 All VTTs by mode and purpose have increased

 Overall, the increase is slightly below the expected increase of +47%

□ small overall impact of ICT changes?

□ Income elasticity of 0.5 seems about right?

 Relatively small changes for commute and business: ICT developments

more important than for other travel?

 Relatively small increases for car (relative to train):

□ important ICT developments for train had already entered the market in 1997?

□ trains more crowded than in 1997?

What do we conclude?

 Beware of internet panels in VTT research!

 Allowing for unobserved heterogeneity (using a panel Latent Class model) increases VTT considerably

□ Much more than the other six differences

 In the period 1997-2009/2011 the average VTT went up by about price

change plus 0.5 times the real income change

□ But differences between purposes and modes that could be related to ICT

developments

For more information

email: dejong@significance.nl or g.c.dejong@its.leeds.ac.uk

Final report and papers:

http://

www.kimnet.nl/sites/kimnet.nl/files/filemanager/bijlagen/Bijlage_Value_of_time_and_ reliability_in_passenger_and_freight_transport_in_the_Netherlands_reprint.pdf

Kouwenhoven, M., G.C de Jong, P Koster, V.A.C van den Berg, E.T Verhoef, J.J Bates and P Warffemius (2014) New values of time and reliability in passenger transport in The Netherlands, Research in Transportation Economics, 47, 37-49

Jong, G.C de, M Kouwenhoven, J Bates, P Koster, E Verhoef L Tavasszy en P

Warffemius (2014) New SP-values of time and reliability for freight transport in the

Netherlands, Transportation Research Part E, 64, 71-87.