The role of design elements on the cost-effectiveness of streetscape improvement

Abstract

This study discusses the effectiveness of contingent valuation methods in evaluating the visual quality of streets. Economic valuation methods provide effective design methods that balance cost-effectiveness with the quality of urban design. Research on conventional contingent valuation methods concentrates on estimating the total value of landscape resources such as forests, wetlands, and parks. In contrast, we assess street design plans from both economic and psychological points of view and analyze by factor analysis the relative importance of design elements such as vegetation, lighting columns, and pavements on the economic and perception-based values. We conducted experiments by using computer-simulated photomontage images as virtual alternatives for two street design projects in Saitama City. The elements considered various types of design with a varying cost of materials for street furniture. The respondents participating in this experiment were asked to evaluate the alternatives by a bidding game method, which is one of the elicitation methods used in contingent valuation. In the economic evaluation of alternatives, the availability of amenities and high design quality of a street are seen as benefits, and these can be compared with the material cost of an alternative. In this study, we use six indices for the economic evaluation of street design that include an acceptable cost derived from a contingent valuation method as well as composite indices related to the cost and benefits (cost ( C), amenity ( A), acceptable cost (AC), A/ C, AC/ C, A − C) and clarify their characteristics indicating cost-effectiveness. Acceptable cost had a strong correlation to the amenity score for each of the two street design projects. In addition, our analysis suggests that AC/ C is highly correlated to low cost plans and that A/ C is a moderate index balancing high amenity value and low cost. We also discuss how these six indices can help planners and designers in making decisions regarding the design strategy of a project. Our results should prove useful in actual street design where cost-effectiveness is an issue.