Principles and Criteria of Lighting Urban Squares (Case Study: Tehran Squares)

Although urban lighting can make a positive contribution to the character and utility of urban spaces, it’s often designed only in respect to the visual welfare and visibility aims. It’s important to consider in all urban space lighting designs that lighting plans in addition to providing visibility, safety and security have to play a key role in improving the function of urban spaces, quality of urban nightlife, image of urban spaces at nighttime, character and identity of urban spaces. This study shows that urban spaces lighting simultaneously have to pursue three main objectives including functional, aesthetic-cognitive and identity-oriented aims. Functional objectives as primary ones are aimed to provide good visibility, safety and security, and to improve nightlife economy, urban tourism and livability of urban spaces at night time. Aesthetic-cognitive objectives can enhance legibility, visual attractiveness, image and orientation in urban spaces at nighttime. Finally the identity-oriented objectives aim to create a strong sense of place and help to maintain the character and uniqueness of urban spaces. Proficiency of an urban lighting designer is to consider these different dimensions of urban spaces’ lighting to benefit from all advantages of lighting plans. The importance of this issue in urban squares is due to their special role in shaping social and physical identity, as one of the main public spaces of cities. This paper aims to reach a lighting design guideline for urban squares which provides a checklist of criterion that is applied in evaluating certain case studies. In order to identify of this guideline, subjective expectations of urban squares are recognized which are spatial determinant, integrity, immobility, and sociability. Spatial determinant in urban squares refers to the sense of enclosure, considering the bounds of space and ease of space perception as a whole by its users. Integrity means the ability of urban square to be consider as a unite space which is not separate to sub spaces. Sociability and immobility of urban squares refers to the ability of these spaces to gather people together and facilitate social interactions in sedentary and immobile behaviors. The second step to reach the guideline is to identify principals of urban spaces lighting in three main categories including contextuality, lighting equipment design, and visual welfare. Contextuality includes four principles namely functional and conceptual compatibility, history and legibility. Lighting equipment design principals categorized in three sub criterion include location and placement, form, maintenance and sustainability of lighting source. Visual welfare includes lighting level, glare limitation, harmonious distribution of brightness and color rendering. Eventually these principals are redefined in a way to enhance the subjective expectations of urban squares. A number of case studies, regional squares in the city of Tehran with various characteristics are chosen and assessed by the systematic self-observation supported by application of evaluation criteria. Findings show that the main purpose of lighting plans in Tehran’s squares is to provide visual welfare. Glare limitation has the highest and color rendering has the lowest significance amongst visual welfare principals in Tehran squares lighting design. Lighting equipment design significantly is the second criteria that has been considered in Tehran squares lighting plan. Findings show that maintenance and sustainability has the highest significance amongst lighting equipment design principals and form is neglected in almost all studied squares. Study of the contextuality in case studies show functional compatibility has the highest significance amongst its principals. Conceptual compatibility has the lowest, history has the second, and legibility has the third significance amongst contextuality principals. Low scores for Conceptual compatibility of lighting plans of Tehran regional squares demonstrate ignorance of identity and historical potential of these places, specially the old ones. As a result, functional qualities such as nightlife, livability, and night economy and cognitive qualities namely image, orientation and legibility have decreased in these urban places. This study show that urban lighting is not a one-dimensional process and purely technical task and in respect to it’s various objectives need to define different methods and principals in each urban spaces and corporation of different professions namely architecture, urban design, urban planning and lighting technical design. Identification of each different urban space lighting principals need accurate recognition and study of the place and its subjective expectations at first step. Study of lighting objectives and users of the place is the final step to achieve the principals of the urban space lighting design.