Generally, people have a good understanding of their local areas. Hence, encouraging them to share this tacit knowledge with local authorities, urban designers and city planners could help improve the quality of public space design significantly. However, persuading people to share their concerns/ideas about their areas, especially through a digital platform, presents a real challenge. One of the main barriers is a lack of trust in the public feedback system. Thus, this research investigates relationships between online trust and service design in order to provide a guideline on how to design the feedback system that addresses users' practical and emotional requirements. A mixed-methods approach was employed to identify key factors affecting online trust and their implications on service design. Six key factors affecting online trust were identified and combined to form a basis for service design guidelines. The outcomes show that service design can support all components required to build trust.