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Introduction
As highlighted over the past few decades, the world is experiencing a drastic increase in population growth in urban settings. Improper consumption of existing resources and increased population rates have also led to growing environmental concerns over the past century (Lerner and Audenhove, 2012). As vehicular traffic increases, additional roads are required to reduce traffic congestion and shorten travel distances. This growing vehicularization leads to a wide variety of social, economic, environmental and health consequences.
To answer the transportation needs of modern society, different methods and solutions have been proposed during the past century, although their side effects have generally been neglected. In particular, different types of urban roads have changed the landscape and highway transportation, directly affecting civil and transportation engineering and urban planning. One of the popular transportation systems, which has been significantly used is elevated highways. Elevated urban highways (UHs) have been seen as the easiest and most efficient solution to solve traffic problems, especially in developing countries (Dessouky, 2017). As a consequence, elevated highways and UHs more generally, have influenced urban design and planning.
UHs are considered as great achievements in urban development projects. For almost a century, their purpose was to contribute to the economic aspect of urban settings and provide access to ever-growing commuting to and from the advancing suburbs. Some researchers claim that such structures result in negative physical and psychological health conditions, increasing the noise and air pollution, especially in residential areas (Appatova et al., 2008). Transportation infrastructures also increase the segregation between local neighborhoods and influence the aesthetic, ecological and historical qualities urban areas (Carmona, 2010; Anuar and Ahmad, 2017; Canter, 1977; Forman et al., 2002; Transportation Research Board, 2002). In particular, highways can act as physical and psychological barriers and create undesirable views, which make the pedestrian experience unpleasant (Trancik, 1986).
Moreover, the spaces under the overpasses, bridges and any kind of urban infrastructures are considered as perilous, neglected places for surrounding environments. Spaces under UHs are often unmanaged “lost spaces” that create complex problems in urban areas (Carmona, 2010). Dumping debris, abandoned cars or illegal activities are mentioned as the negative impacts of these infrastructures (Trancik, 1986; Anuar and Ahmad, 2017). A resultant lack of security and fear of violence further...