**1. Introduction**

Our streets are currently undergoing a transformation that might lead to a substantial change in the way valuable urban space is allocated, and, consequently, in the way it is designed. Back in time, streets were public spaces essential to our social needs (i.e., provision of recreational space and places to enhance social links [1]), cultural needs (i.e., cultural heritage preservation and provision of sense of place [2]), and economic needs (provision and sustainment of economic interchange places [3]), transportation notwithstanding [4,5]. In time, a change for streets involved the introduction of automobiles to the urban scene. The speed of motor vehicles and the demand for additional road capacity were the two main factors that affected the allocation of street space. Nowadays, streets have been rethought to make that space serve more functions than mere transportation. Green streets, or streets that devote some space for green infrastructure (GI) with an environmental purpose, are an example of this.

More green areas are required in cities for social, economic, and environmental purposes; however, there is limited space within the built environment to allocate GI. Cities and towns have been growing in such a way that some basic environmental services have been seriously affected and their delivery compromised [1]. The provision of GI within the built environment contributes to alleviating, mitigating, or resolving environmental problems that include heat island effect [6], non-regulated runoff speed [7], or urban noise [8] at local and global scale and to enhance the quality of life.

**Citation:** Rodriguez-Valencia, A.; Ortiz-Ramirez, H.A. Understanding Green Street Design: Evidence from Three Cases in the U.S. *Sustainability* **2021**, *13*, 1916. https://doi.org/ 10.3390/su13041916

Academic Editor: Ken Tamminga Received: 2 December 2020 Accepted: 18 December 2020 Published: 10 February 2021

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GI requires land and cities might not have enough free, empty, or underutilized space to house enough GI to cope with the demand. This limitation has shifted the attention to the rights-of-way (streets) to provide these services, because they are numerous, accessible, and evenly distributed public lands. The rights-of-way (ROW), however, are heavily regulated public spaces, where design is standardized, ruled by codes and manuals. But some cities have found mechanisms to make green streets a common practice within ROW.

The original purpose of this paper is to better understand green street design, analyze how it differs from the traditional standardized and rigid transportation-landscape design approach, and unveil general design commonalities based on case studies. This paper qualitatively revises the processes in three US cities to understand how green infrastructure was considered and included in the traditional standardized and rigid transportationlandscape design procedure. Since all cases are related to stormwater management, this paper also contributes to understanding the assessment of the environmental service that justifies the process. A qualitative case study methodology was grounded in in-depth multi-agent interviews, documentary information, and on-site visits.
