Engineering in Plain Sight

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4 Bridges and Tunnels

Introduction

For all its natural beauty, the Earth often creates difficulties in getting around. In fact, many of the most magnificent of Earth’s features are also the most challenging to traverse. Rivers and mountains aren’t conducive to roadways, railways, or other corridors along the ground’s surface. When the topography is too wet, steep, treacherous, or prone to disaster, the only way forward is up or down. At canyons, valleys, and rivers, our roadways break free from the earth using bridges. And at hills, mountains, and shallow waterways, they bore right through to the other side. Perhaps because these structures ...