Overall, while both tunnels were constructed in different settings—one under a river and the other beneath a city—the second tunnel is significantly larger in both length and capacity, despite being built more quickly. However, this larger scale came with a much higher financial cost.
The first tunnel, constructed in a sandy environment beneath a river and crossed by a bridge, extended 2.2 kilometers in length and was 1.5 meters deep underground. This project spanned 12 years, from 1986 to 1998, and was completed at a cost of $555 million. By comparison, the second tunnel, built in a dense urban area with a terrain of stone and clay, was much longer, measuring 3.6 kilometers, and was located at a depth of 2.5 meters. Despite the increased complexity, this tunnel was completed in just four years, between 2002 and 2006, at a cost of $1.1 billion.
In terms of capacity, the second tunnel could accommodate six lanes of traffic, making it significantly more efficient than the first tunnel, which only had four lanes. The greater size and capacity of the second tunnel are likely reasons for its higher cost, despite its shorter construction timeline.