Variable selection and construction

In order to highlight the different psycho-social factors behind modal choice, we used logistic and linear regressions of various psychological constructs (independent variables) on three different measures of observed behaviour (dependent variables).

Dependent variables

Observed dependent behaviours included in the models will take three forms, all based on self-reported behaviour:

- one binomial modal choice for the most frequent trip, labelled as “ModBin”, which provides two modes: (1) “private”, for people using a motorized two-wheeler or a car – either as driver or passenger – and (2) “pt/soft” for people using public transport or soft mode;

- one trinomial modal choice for the most frequent trip, labelled as “ModTrin”, which provides three modes: (1) “private”, for people using a motorized two-wheeler or a car – either as driver or passenger – (2) “pt” for people using public transport and (3) “soft”, for people riding a bicycle or walking for their most frequent trip;

- one continuous variable representing a sustainable personal mobility index, labelled as “SusMobIndex”, which ranges from 0 to 1 and has been built as a weighted mean of self-reported frequencies of use of the different modes. The formal definition is given by equation 12:

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= 1 − ∑_∑ (12)

where is the weight for mode and the weekly frequency of mode . Table 5 summarises each mode and their corresponding weight.The weight is related to the gross estimation of CO2 emissions produced by the different modes: 104 grams of CO2/p*km

for car, 72 grams CO2/p*km for two-wheelers and 35 grams of CO2/p*km for public

transport (EEA, TERM report, 2014 ; Kenworthy, 2003)

Table 5:Values of the weighting parameters used in SusMobInd

Car 1

Two-wheeler 0.66 Public transport 0.33 Bicicle/walk 0

It is worthy to note that this index does not consider the distance travelled nor the exact number of trips actually made. However, it is a gross indicator of environmentally- friendly trips per individual for a typical week, according to the his/her mobility habits.

Psychological constructs

Latent psychological constructs were produced using Confirmatory Factor Analysis (CFA) on questionnaire items. Three constructs are exclusive to the NAT: Problem Awareness (PA); Adverse Consequences (AC) and Ascription of Responsibility (AR). The TPB and TIB have both one exclusive construct: Attitude (ATT) for the TPB and Affect (AFF) for the TIB. The Personal Norms construct is common to NAT and TIB whereas the Perceived Behavioural Control (PBCb & PBCpt) and the Subjective Norms constructs are common to the TPB and the TIB.

The Personal norms (PN) construct was assessed with two items: (PN1) “People should be allowed to use their car as much as they like, even if it causes damage to the environment” and (PN2) “A sustainable mobility would allow an improvement of the quality of life in the city of Torino”. The answers were collected on 5-points Likert scale where 1 was labelled “I totally disagree” and 5 “I totally agree”. Moreover, PN1 has been recoded using reverse-scoring, to reflect a positive statement toward the environment.

57 The Problem Awareness (PA) construct was assessed using three items: (PA1) “Air pollution is a real problem for the city of Torino”; (PA2) “Noise pollution is a real problem for the city of Torino”; and (PA3) “Road accidents are a real problem for the city of Torino”. Answers were collected on 5-points Likert scale where 1 was labelled “I totally disagree” and 5 “I totally agree”.

The Adverse Consequences (AC) construct was assessed using two items: (AC1) “Traffic jams are a real problem for the city of Torino” and (AC2) “Traffic jams worsen air pollution”. Answers were collected on 5-points Likert scale where 1 was labelled “I totally disagree” and 5 “I totally agree”.

The Ascription of Responsibility (AR) construct was assessed with two items: (AR1) “Respect toward the environment” which was assessed by asking the respondents the level of importance for choosing the mode of transport for their most frequent trip and (AR2) “It is my personal responsibility to reduce the emission of greenhouse gases that induce climate-change”. Answers were collected on 5-points Likert scale where 1 was labelled “I totally disagree” and 5 “I totally agree”.

The Subjective Norms (SN) construct was assessed with two items: (SN1) “I expect public policy makers put pressure on me to reduce the environmental impacts of my travels” and (SN2) “I expect my family and friends put pressure on me to reduce the environmental impacts of my travels”. Answers were collected on 5-points Likert scale where 1 was labelled “I totally disagree” and 5 “I totally agree”.

The Affect (AFF) construct towards cars was assessed using one item: (AFF1) “I like travelling by car” which was measured using a 5-points Likert scale where 1 was labelled “I totally disagree” and 5 “I totally agree”.

The Perceived Accessibility (PAC) construct was assessed using four items: (PAC1) “Public Transport is available for my most frequent trip”; (PAC2) “My personal bike is available for my most frequent trip”; (PAC3) “The bike-sharing service is available for my most frequent trip”; and (PAC4) “I can walk for my most frequent trip”. Answers were collected on 5-points Likert scale where 1 was labelled “I totally disagree” and 5 “I totally agree”.

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The Perceived Behavioural Control has been split into two independent constructs. Firstly, the Perceived Behavioural Control toward bicycle use (PBCb) was constructed using two items: (PBCb1) “I would use the bike more frequently if the cycling infrastructures were better” and (PBCb2) “I would use the bike sharing service more frequently if I had real time information on their availability and on the stalls' occupation”. Secondly, the Perceived

Behavioural Control toward public transport use (PBCpt) was constructed using three

items: (PBCpt1) “I would use the public transport more frequently if the vehicles (bus, metro, Tram) were better”; (PBCpt2) “I would use the public transport more frequently if the stops were better equipped”; and (PBCpt3) “I would use public transport more frequently if I had real time information about arrival times at all the stops”. Answers were collected on 5- points Likert scale where 1 was labelled “I totally disagree” and 5 “I totally agree”.

Transport related Values were explored using an Exploratory Factor Analysis (EFA) on items where respondents were asked, on a 5-point Likert scale (where 1 was labelled “Not important at all” and 5 “Extremely important”), the level of importance of choosing their mode of transport for their most frequent trip, according to different reasons. Such reasons were “Cost”, “Speed”, “Comfort”, “Pleasure (I like this mode of transport)”, “Flexibility and independence”, “Respect towards the environment” and “Reliability of travel time”. The Exploratory Factor Analysis (EFA) was conducted using the Maximum Likelihood method and the rotation of the factor was performed using the oblique Quartimin criterion that allows correlation between latent factors (Fabrigar, 1999). The EFA produced a 2 factors solutions which have been named Utilitarian (U) and Convenience (C) values

Another independent variable included in our analysis is the Home localisation

(Home) which was divided into three categories: Urban (U), SubUrban (SU) and Rural (R).