Contribution to the relevant literature
The methodology we implemented to select PSUM indicators is based on two main tools: 1) a conceptual framework of dimensions and objectives of PSUM, which is used to select a first core set of performance indicators; 2) the participation of citizens and stakeholders, in order to rank the selected indicators and—depending on the available resources—cut off the less relevant ones. The used methodology explicitly refers to the theoretical and practical work of two research groups, led by Mark Reed and Jacquelin Burgess, respectively [14, 20].
As far as we know, no reference can be found in the literature to the application of such an integrated methodology to the issue of sustainable urban mobility: many studies explicitly consider the dimensions of environmental, social and economic sustainability, some of them refer to objectives of policies for sustainable transport, but only two [21, 22] are based on the participation of stakeholders (and not of citizens) in order to select a limited number of indicators from a much longer initial list.Footnote 12
We may then conclude that the main contribution of this study to the relevant literature is the integration of the participation of both citizens and stakeholders into the selection of PSUM indicators. The remaining part of this section discusses separately the three steps of the implemented procedure and its results.
Discussion of step 1 (a conceptual framework)
Though the definition of the initial conceptual framework is not the objective of our research (nor its added value), it must be emphasized that the starting reference to an already partially developed framework constitutes the main limitation of this study. We integrated the first version of the framework on the basis of a review of the relevant literature and meetings with other experts, but we remain aware that it needs further improvement. Inter alia: the objectives of urban density and social inclusion should be explicitly considered; all indicators—especially in the case of practical applications—should be better specified in order to check the availability of data and associate quantitative targets to objectives. At the same time, we remain convinced of our choice of referring to generic objectives and not to specific actions; otherwise the acceptability of a policy, instead of its relevance, is likely to be assessed.
Discussion of step 2 (ranking of PSUM objectives)
First of all, it must be said that we had to repeat the national survey after interviewers reported that respondents found some questions hard to understand. This is why we needed to clarify, for example, the difference between greenhouse gasses and local air pollutants, and between land consumption and the occupation of urban space; moreover, we had to add some practical examples to explain what we meant by ‘waste generated by mobility’. It remains that some respondents could have responded superficially, without signalling to the interviewer that they did not completely understand the question.Footnote 13 This is a problem which could be managed only by direct contact with citizens: ex-ante, through focus groups aimed at reaching a shared terminology; ex-post, through structured arena, where citizens could deliberate on the results emerging from the survey.
There is one striking result emerging from the national survey: the objective of ‘reducing private transport costs’ ranks 2nd, which seems not so much consistent with the other high ranking objectives (‘reducing greenhouse gases’, ‘reducing air pollutants’, ‘increasing safety’, etc.). Actually, one should consider that most citizens are car drivers, who aspire at a more sustainable urban environment and—at the same time—are budget conscious; such an interpretation is confirmed by data segmentation: the need of reducing private costs ranks 5th in big cities (were the % of car drivers is lower) and 6th for public transport users. In more general terms, the analysis of the results of the national survey by urban size and transport mode shows that opinions on objectives of PSUM depend on the size of the city where citizens live and on their actual mobility behaviour.
Stakeholders’ appraisal was more consistent: the objectives of easing private mobility and reducing its costs have been positioned at the bottom of the ranking; moreover, stakeholders did not explicitly refer to specific situations (even if one should suppose they generally refer to metropolitan contexts). Most important, though stakeholders were assigned the burdensome task of carrying out 52 assessments (13 objectives against four criteria), deliberation was easier than expected: the assignment of reaching shared evaluations pushed the mutual understanding between involved parties and the arrangement of all interests at stake. During the “dialogue”, stakeholders acted as experts too; that is, they suggested some integrations to the proposed framework: in particular they asked for the explicit consideration of the issue of densityFootnote 14 and a greater articulation of the dimension of economic sustainability.
Discussion of step 3 (selection of PSUM indicators)
The two selections of PSUM indicators—based on citizens’ opinion and stakeholders’ appraisal, respectively—depend on the level of the thresholds which are used to cut off the less relevant indicators (see Table 6). When lower thresholds are used, only four performance indicators are shared between the two resulting sets: ‘CO2 from transport’, ‘Quantity and quality of public transport’, ‘PMx, COVNM, NOx, CO from transport’, ‘Deaths and injuries from traffic accidents’ (and only one indicator is cut off from both lists: ‘congestion’). When higher thresholds are used, the two sets show no intersection.
There is no immediate explanation for the divergence between the two selections. We can only stress one relevant difference in the composition of the selecting groups: on one side, car users are almost 85% of the sample, which implies that their opinion strongly influences the results of the national survey; on the other side, only one stakeholder (out of 13) directly represented the interests related to the car. Moreover—as already stressed—all representative of the involved stakeholders live in a metropolitan context where the car is less used, and alternatives to the car are more diffused. Finally, it must be said that we had planned for stakeholders to know the evaluations of citizens before starting their “dialogue”, with the purpose of reducing the risk of generating equivocal results, but this was not possible because the results of the national survey were not available when the stakeholder dialogue started (a delay caused by the already mentioned repetition of the national survey).