The figure shows two distinct underground tunnels constructed in different Australian cities, which were built between 1986-1998 and 2005-2006 respectively. Both projects have varying dimensions, locations and costs.
The first tunnel was constructed under a bridge and a water body, and goes 1.5 meters deep and is 2.2 kilometers long. Meanwhile, the second tunnel was built under the city’s buildings and roads. The newer tunnel is also deeper (2.5 meters) and longer (3.6 kilometers) in comparison to the older one.
The first tunnel lies under a bed of sand while the latter is surrounded by stone and clay. It induced a cost of $555 million, while the latest tunnel’s development cost $1.1 billion dollars. This higher cost can be attributed to its greater depth, length, along with a greater width that increases the road’s capacity to three cars traveling simultaneously. On the other hand, the older tunnel only has two lanes per road.
Overall, these two tunnels have different outlooks and are likely designed to serve different purposes for underground travel within the Australian cities.