Why tunnel instead of bridge?

Why tunnel instead of bridge?" This is a question that often arises in the context of infrastructure planning and engineering projects. Tunnels and bridges are both viable solutions for crossing obstacles such as rivers, valleys, or mountains, but each has its unique advantages and disadvantages. Tunnels offer the advantage of preserving the natural landscape above ground, avoiding the visual impact of a bridge. They can also provide a smoother, more direct route, especially in mountainous terrain where bridges may require steeper grades or longer spans. However, tunnels can be expensive to construct and maintain, and they may pose unique engineering challenges such as groundwater management and ventilation. Bridges, on the other hand, can be less expensive to build and may have a smaller impact on the environment during construction. They also offer a more open and scenic route, providing views of the surrounding landscape. But bridges can be visually intrusive, especially in sensitive environments, and may require additional land for piers or abutments. So, the decision to choose a tunnel over a bridge ultimately depends on a range of factors including cost, engineering feasibility, environmental impact, and community preferences. It's a complex question that requires careful consideration of all these variables.