As for the asphalt pavement, the authors considered that
layering works are done in two parallel strips, each half the
width of the tunnel. The method has been adopted because it is
impossible to pump the bituminous concrete.
Construction costs were estimated using Italian road price lists;
for both tubes, they are listed in Table 1.
The maintenance plan takes into account the damage
induced by traffic and the management procedures reported in
the literature (Holt et al., 2011; Scheving, 2011; Torres-Machi
et al., 2014).