Questions about who are citizens and who should participate in planning endeavors have been long debated ^[1][2][16,17]. Decisions may be skewed if only stakeholders or highly interested people participate in planning processes. The opinions of the majority are understated, although mere majority rule is not always the dominant decision imperative. Deliberative democracy has developed the concept of mini-publics to tackle such questions, in which randomly chosen citizens participate in the planning processes ^[3][4][5][18,19,20]. The premise of mini-publics assumes that randomly selected individuals should be representative of the public at large and that the decision should be reasoned if they deliberate in an appropriate manner. It will lead to political trust and legitimacy if these assumptions are fulfilled ^[6][21]. The idea of mini-publics has been widely adopted in many nations, including Japan. Such collectives are sometimes called citizen jury ^[7][22], planning cells ^[8][23], deliberative polling ^[9][10][24,25], and consensus conference ^[11][26]. However, mini-publics are insufficient on their own to undertake the entire consensus process of planning because the concerns and values of stakeholders should also be considered. Therefore, a hybrid participatory program labeled “cooperative discourse” was proposed for a decision-making process that engages experts, stakeholders or people with a vested interest, and a citizen panel representing the entire region ^[12][27].

Although cooperative discourse has provided useful insight and good practices, a failed instance of such hybrid participation was reported because the stakeholders did not approve the decision proposed by the randomly chosen citizens ^[13][28]. Such failed experiences offer the lesson that stakeholders need to consent to the decision procedure in advance and should be accorded the opportunity to join the dialogue after the citizen panel comes to a decision. However, the process should also ensure that stakeholders respect the assessments and counsels of the citizen panel. Therefore, participatory programs should be carefully designed with regard to the when and how of involving stakeholders and citizen panels in the stepwise planning process ^[14][29].

The functions of the citizen panel in the decision process should be elucidated and differentiated in designing participatory programs. The present study classifies the functions along the decision process in terms of procedural fairness, of which the antecedents and components are helpful for the evaluation of participatory programs ^{[15][16][17][18]}[11,30,31,32]. It is widely recognized that citizens should be accorded with opportunities to express their opinions and that diverse opinions should be reflected in the policy plan ^[16][19][30,33]. The opportunity to express opinions and the reflection of the opinions are lumped together as “reflection of voices”, which is one of the most widely applied criteria in procedural fairness adjudications ^[20][21][22][34,35,36]. The inclusion of the voice entails the necessity of the involvement of citizens in the early stage of the planning; otherwise, it is difficult to reflect their opinions. Repeated opportunity is also a requisite of the criterion of correctability, a prime element of procedural fairness ^[23][37]. Moreover, it is crucial for proposed plans to be assessed before they are finalized. The citizen panel performs the function of value consultation: members of the citizen panel assess the proposed plan in terms of both outcome and process ^[8][24][23,38]. Notably, the roles discharged by participants during the planning process should be distinguished. In particular, the participants of citizen panel taking a role of value consultation should be differentiated from the participants attending the occasion making voice during preceding stages. To be feasible and acceptable to the broader public, the validity of the proposed plan should be assessed by third parties not engaged in the preceding stages. Nevertheless, although plural opportunities in the planning process have been recorded in some programs, existing citizen participation instances have not always explicitly delineated the functions of the citizen panel during the planning process ^[25][39]. This study proposes a stepwise participatory program that encompasses both stakeholders and citizen panels, clearly differentiating the functions of the citizen panels according to the stages of the planning process. The roles discharged by the participants in the proposed program vary from the early to later stages. Diverse values of the proposed plan are discovered and reflected upon in the initial stages and are subjected to consultative discussions in the later stages.

Backcast scenario workshops are widely adopted for participatory programs for planning sustainability goals. Such situational programs invite participants to imagine an ideal future and conceive the conditions required to achieve it ^{[26][27][28][29]}[40,41,42,43]. In contrast, forecasting begins with the current position, determines the current difficulties, and seeks solutions for them. While forecasting is suited to immediate and short-term problem-solving, it is not apt for long-term visioning. Policies geared toward sustainability should consider the demands of future generations; hence, backcasting is more suited for seeking and setting goals to be achieved ^[25][39]. However, backcasting is not an omnipotent methodology. The established goals may be too ideal, and it may be difficult to evaluate their feasibility. Furthermore, the goal-sharing measures may sometimes be neglected. The goals described in the proposed plan become meaningful when the broader public, not only participants, share the goals because broader public cooperation is required to achieve sustainability-related objectives. Participants joining the planning process are quite few in the population, while the vast majority is nonparticipants. Those who do not participate in the planning process are sometimes unaware of the goals to be shared, making the effected policies less likely to succeed. Therefore, the appraisals of citizens who have not participated in the preceding stages should be involved in the planning process. 

Previous research endeavors have recommended that participatory programs should be evaluated for their efficiency in planning better development methods ^[14][17][29,31]. In particular, it has been suggested that people who did not participate in such programs should evaluate the planning process because of the critical importance of both participants and nonparticipants accepting the plan ^[17][31]. If such processes are not implemented, a given plan is unlikely to be effective because environmental sustainability strategies require widespread public cooperation. This study explores the effects of public participation programs that emphasize procedural fairness and demonstrates that a fair process of stepwise decision-making based on citizen participation fosters greater public acceptance of new sustainability plans.

This study focuses on procedural and distributive fairness to investigate factors relevant to public acceptance because fairness is closely related to public participation. A vast volume of social psychology literature reveals that public acceptance and policy support are inseparable from issues pertaining to procedural and distributive justice ^{[23][30][31][32]}[37,44,45,46]. Distributive fairness concerns outcomes and consequences ^[21][23][35,37] emanating from the allocation of resources, rewards and costs, and benefits and harms ^[33][34][47,48]. Distributive fairness is prioritized in public decision-making as it focuses on the criteria required to ensure a positive outcome for an entire society ^[33][47]. For example, it is widely recognized that for a sustainability plan to be successful, it should aim to benefit all parties to be affected, including future generations. On the other hand, procedural fairness concerns the processes of allocating resources and decision-making with respect to the design of plans ^[21][35]. This aspect encompasses the procedural components of the social system, including both prelegal decision-making and legal progressions ^[21][23][35,37]. Specific measures must also be employed to assure a fair process of public decision-making. It has been argued that both distributive and procedural fairness are essential for the acceptability of environmental policies ^[35][5]. Procedural arrangements are inseparably connected to the acceptance of policymaking decisions ^[36][49]. Significantly, fair decision-making processes are emphasized when it is challenging to achieve public acceptance ^[37][50].

Procedural and distributive fairness are comprehensive concepts; therefore, many antecedent factors have been identified ^[23][30][31][37,44,45]. The relevant antecedent factors of procedural and distributive fairness must be selected on a case-by-case basis ^[38][15], cognizing the specifics of instances.

In ascertaining the antecedent factors to be measured in participatory programs for sustainability planning, openness, the reflection of myriad voices, and representativeness were identified as the three relevant antecedent factors of procedural fairness. The rationale for the selection of these three constituents is outlined as follows. First, openness assures transparency, including information disclosure, and provides everyone the opportunity to participate. It is thus a general principle of the evaluation of any process ^[16][17][19][30,31,33]. Second, the reflection of voice is a critical criterion of the assessment of participatory program practices ^[16][17][19][30,31,33]. If a program is not reflective of voices, the significance of a participatory program is lost, regardless of the number of citizens accorded the opportunity to express their opinions. Moreover, the opinions voiced should be reflectively inclusive: they should incorporate the views of both the majority and the minorities to be affected. If people perceive that an inclusive range of participant opinions is not indicated in the plan, the program is likely to be regarded as just a means of enabling some citizens to vent their views while the procedure itself remains unfair. Finally, representativeness denotes whether the participants exemplify all citizens. It is thus also an essential factor for the evaluation of a participatory program ^{[16][17][19][23]}[30,31,33,37]. If people perceive that the program only epitomizes those who are extremely interested in the issue, the program will be deemed biased and illegitimate, and by extension, the process will be adjudged as unfair.

Public benefit, the effectiveness of sharing common goals, and feasibility were identified as the relevant antecedent factors of the evaluation of expected outcomes for sustainability-related participatory programs. Public benefit refers to the desirability of the program for all of society, which is a crucial factor as the plan is intended to promote desirable sustainable goals that would benefit all residents. However, the mere description of a goal is not enough to actually achieve the objective. A set goal will remain ineffective unless it is translated into an objective shared by many people and thus becomes a common understanding. This step is crucial because the very formation of the awareness of common goals suggests that society is moving toward the goal. Therefore, it is necessary to endeavor to promote the desired goals widely across all sections of society. This outcome is described as the effectiveness of sharing common goals. If people perceive that it is effective to share the common goals for the achievement of the targeted objectives, their expectations for the plan’s outcome will be positive. Finally, feasibility is also crucial for outcome evaluation: if people perceive the plan to be unattainable and unrealistic, they will not expect the plan to produce a good outcome regardless of their perception of the ultimate goal as acclaimed.