# Sustainability Analysis of the M-30 Madrid Tunnels and Madrid Rio after 14 years of Service Life  
[PERSON]  
Departamento de Ingenieria Civil, Construccion, E.T.S de Ingenieros de Caminos, Canales y Puertos, Universidad Politecnica de Madrid, c/Professor [PERSON], s/n, 28040 Madrid, Spain; [EMAIL_ADDRESS] (L.L.-d.A. ); [EMAIL_ADDRESS] (A.P.P.-F); [EMAIL_ADDRESS] (M.G.A. ); [EMAIL_ADDRESS] (T.R.) 1 October 202020  
200,000 vehicles/day [8]. Its total length is about 32 km, with a generic configuration of 3 + 3 lanes except on the north part where it is an urban boulevard [1]. It was built during the 1970s and 1990s with a heterogeneous design, combining sections with highway and urban characteristics regulated by traffic lights. Although this diversity of sections still exists, during its first years the M-30 encountered issues which concurrently compromised road safety in the area (an average 600 accidents and eight deaths per year from 1998 to 2002, [9]). One of the main reasons was an excessive amount of entrances and exits from the main stem and several (and too short) transfer sections between side and central lanes [9]. Furthermore, the M-30 is located in close proximity to the city center and crosses built-up areas, which has caused several environmental problems such as noise and air pollution [10]. These issues were especially severe on the west sector where the highway flowed over an extremely developed area, causing a significant barrier effect [9]. Therefore, a renovation of layout was needed to improve socio-economic and environmental conditions. In such a way, renovation (carried out from 2004 to 2007) sought to increase the road service level and improve comfort and environmental conditions both of the road and the surrounding areas. Road service level was improved by homogenizing and relocating part of the road underground (with 8.8 km of tunnels being constructed [8]), reducing the accident rate and traffic congestion in the area. Such comfort and environmental conditions were improved by creating a new green corridor located in the south-west part of the city, Figure 1[10]. This corridor aimed to decrease the environmental impact and fluency problems caused by the barrier effect of the road in nearby neighborhoods [8; 9; 10]. Figure 1: Location of the M-30 ring-road and surrounding districts. South-west area renovated in 2004–2007 to build the tunnels and Madrid Rio park is highlighted in red. In this study, the sustainability analysis of the M-30 focuses on the works performed in its south-west stretch. This area was that most influenced by the new road design due to the burial of the layout and creation of a new green corridor, and public open space, named Madrid Rio. The tunnels of this section were built through use of two typologies: an opencast tunnel with screen walls and a false ceiling (next to the Manzanares river) and a tunnel built by using two tunnel boring machines (TBMs) (a by-pass stretch, as shown in Figure 1) [11]. The tunnels offer high safety measures, such as accident and fire prevention, as well as several units and devices to control and ensure a suitable air quality. Indeed, they are fitted with a high amount of ventilation stations with ventilation areas about 600 m long to dilute the pollutant concentration inside of the tunnels [12]. Madrid Rio is a linear park with 429 hectares of new green areas distributed along the banks of the Manzanares river with the aim of integrating the river environment into the urban landscape of Madrid [13]. Thus, the park offered not only an improvement of the environmental conditions but also eliminated the previous road barrier, linking the south with central Madrid, thus producing extensive urban regeneration of the area [14]. The materials used to build the tunnels should also be taken into account, as it is known that cement production contributes to global warming with 7-8% of global CO\({}_{2}\) emissions [15].