Evaluation of the Literature on the Use of Space Underneath Elevated Highways in Urban Leftover Space Renewal

The construction of urban highways within and around the city has resulted in a significant amount of residual spaces, which are rarely incorporated into official planning and design efforts. This literature review paper provides an overview of space underneath elevated highways delivered by urban leftover space: What types of leftover space have been discussed? Which underneath elevated highways have been identified in leftover space? 112 scientific papers were analyzed for their 1) leftover space terms applied, 2) space underneath elevated highways studied, 3) current or potential underneath elevated highways discussed. Through the review, we found that although different types of space have been identified in leftover space, most studies did not consider underneath elevated highways synergies and trade-offs. The literature review highlights two knowledge gaps for future research: Firstly, the existing research on residual space under urban viaducts has been exhaustive in terms of connecting with environmental attributes. Secondly, the content of the social interaction and use of the remaining space under the viaducts can be connected to the content of the environmental attributes. The existing gaps in the research indicate the importance of exploring the potential impacts aimed at utilizing leftover spaces. By highlighting the value of the environmental attributes of under-bridge spaces, the literature study promotes the recognition of the association of social interactions with the environmental attributes of under-bridge spaces and further outlines future research directions for the remaining under-bridge spaces in the urban design process.