*5.9. Urban Greenways Typology*

The typology of urban greenways described in Section 4 above illuminates some noteworthy traits of urban greenways. In urban centers, greenways are often implemented in highly constructed landscapes that formerly served another purpose. This is exemplified in the Cheonggyecheon freeway-to-greenway, as well as the Rose Kennedy Greenway. Colloquially known as the "Big Dig," this project depressed the Central Artery of Interstate 93—an elevated six-lane highway completed in 1959—and in its place created a 1.5-mile greenway through the heart of the city (see Figure 6). This reflects a late 20th and early 21st century urban parks movement to repurpose and adaptively reuse outdated landscapes such as landfills, elevated rails and highways, and parking lots [32]. It also reflects efforts to redesign the auto-centric landscape that dominated mid-20th century urban planning.

**Figure 6.** (**A**) The Central Artery highway running through the city in 1962. (**B**) Rose Kennedy Greenway in 2017 following depression of the Central Artery. Photo A: Reproduced with permission from the Massachusetts State Archives. Photo B: Reproduced with permission from the Rose Kennedy Greenway Conservancy, photo: ©Kyle Klein

Another contemporary expression of this aspiration is the active travel corridor exemplified in Boston's Emerald Network initiative and the Comox-Helmcken Greenway in Vancouver, Canada (see Figure 7). A unifying theme in these greenways is the redesign of existing streets to accommodate cyclists, including infrastructural interventions, such as: (1) new and upgraded traffic signals; (2) new street paving, concrete medians and curb bulges, catch basins, paint, and signage; (3) new sidewalks, curb ramps, and raised crosswalks; (4) new and upgraded street, sidewalk, and park lighting; and (5) new public realm amenities, such as seating, planting, trees, drinking fountains, and wayfinding features [49].

Similar to the freeway-to-greenway and rail-to-trail examples, these contemporary expressions of urban greenways adaptively reuse existing urban landscapes for new purposes. From a planning perspective, these adaptive reuse types of greenways can be considered an "offensive strategy," in that they introduce new elements in previously disturbed or fragmented landscapes [1]. This resonates with depictions of urban greening as a social practice of organized or semi-organized efforts to introduce, conserve, or maintain outdoor vegetation in urban areas [87,88]. In many cases, adaptive reuse greenways include new plantings and a net increase in flora and biomass. This may not, however, always be the case with active travel corridors, where new plantings are just one of many structural design elements and many stretches may have little if any vegetation.

**Figure 7.** The Comox-Helmcken streetscape before (**A**) and after (**B**) greenway construction. Photo A: Google Street View; Photo B: Reproduced with permission from Paul Krueger, City of Vancouver

This represents a departure from the original conception of greenways, where "green" is synonymous with "nature" or "flora" [4,5,19]. In urban areas, by contrast, "green" coupled with "ways" can signify a broader sustainability and livability agenda. This reflects popular and scholarly discourse on "green cities," which addresses topics including transportation, energy, food systems, and social equity, and climate change in particular [89–92]. The lack of much vegetation in contemporary expressions of greenways as active travel corridors might be perceived as corrupting the greenway construct. It is worth noting, however, that related terms have undergone similar changes. For example, early conceptualization of "green infrastructure" had a strong wildlife conservation orientation that drew upon landscape ecology as a strategy to protect and restore regional hubs and corridors of natural lands/habitat from development [18,93]. The term, however, also became synonymous with low-impact development and stormwater management, where the primary goal is to hold or infiltrate stormwater directly in the ground—often but not always through vegetated systems—instead of channeling runoff into traditional grey infrastructure culverts and pipes that discharge into nearby surface waters [94–96]. Some have even extended the green infrastructure construct to include solar panels, wind turbines, public art installations, and outdoor theaters [97].

Another noteworthy theme of urban greenways is that they exist along a naturalistic to highly constructed continuum. This is clearly the case for freeways-to-greenways, rail-to-trails, and active travel corridors, all of which are new constructions layered upon previous constructions. It is also the case for nature trails, which can include compacted gravel and paved paths as well as constructed bridges. This also applies to waterfront greenways in urban centers, which tend to have hardened shorelines and are often built on fill. But as riverfront greenways extend from urban centers to less densely developed landscapes, the waterfront can assume an increasingly naturalistic condition, as exemplified in the Schuylkill River Greenway in Philadelphia, USA. In some cases, urban greenway planning can include regrading and planting of vegetation to actively restore waterfronts to a naturalistic condition, as exemplified in the Chicago River corridor [98].
